DEV Community: jia yuying

Why EV Battery Heaters Fail: 7 Engineering Mistakes in Thermal Design

jia yuying — Wed, 14 Oct 2026 06:05:45 +0000

Designing EV Battery Heating Systems: The Thermal Problems Engineers Need to Solve

When engineers start designing an EV battery heating system, the first question is often:

"How much heater power do we need?"

It is an important question, but it is usually not the first problem that needs to be solved.

A battery heater with higher wattage does not automatically create a better thermal solution.

In real EV battery applications, heating performance depends on much more than electrical power. The actual challenge is moving thermal energy from the heater to the battery cells efficiently, uniformly, and safely.

A practical battery heating design needs to consider:

Thermal path
Heater placement
Heating uniformity
Power density
Thermal interface resistance
Temperature sensing
Control strategy
Mechanical reliability

The heater is only one part of the system.

Problem 1: The Heater Generates Heat, But the Battery Does Not Warm Evenly

One common issue in battery heating design is assuming that generating more heat will solve the problem.

In reality, the key question is:

Where does the heat go?

A simplified thermal path looks like this:

Heater
   ↓
Thermal Interface
   ↓
Battery Module Structure
   ↓
Battery Cells

Every layer in this path affects performance.

If thermal contact is poor, heat transfer efficiency decreases.

If heating is concentrated in a small area, local hot spots can develop while other areas remain cold.

This creates temperature gradients inside the battery module.

For lithium-ion batteries, temperature uniformity is often more important than simply increasing the average temperature.

Problem 2: Selecting Heater Power Without Understanding Thermal Requirements

A common design mistake is choosing heater power based only on battery size.

The required heating power depends on:

Battery mass
Starting temperature
Target temperature
Required heating time
Heat loss
Thermal conductivity
Installation environment

A basic thermal relationship is:

Q = m × Cp × ΔT

Where:

Q = required thermal energy
m = mass being heated
Cp = specific heat capacity
ΔT = required temperature increase

The final heater power should also consider heat loss and system efficiency.

A 200 W heater may perform well in one battery design and poorly in another.

The surrounding thermal structure matters.

Problem 3: Heater Placement Is a System Design Decision

The location of the heater can influence performance as much as the heater specification itself.

Possible installation methods include:

Directly heating the battery module surface
Heating through a metal heat-spreading plate
Installing near a thermal interface layer
Heating specific areas that require temperature control

The best location depends on the battery architecture.

A heater should be placed where thermal energy can enter the battery effectively.

The question is not:

"Where can the heater physically fit?"

The better question is:

"Where can heat be transferred most efficiently?"

Problem 4: Temperature Sensors Can Create False Feedback

Battery heating systems rely on temperature feedback.

However, sensor placement can create unexpected control problems.

For example:

A heater may be installed near the bottom of a module, while the temperature sensor is located several centimeters away.

The heater area may already be warm, but the sensor still detects a lower temperature.

The control system may continue heating.

This can increase temperature differences inside the battery.

A better design considers:

Heater location
Heat spreading
Sensor position
Expected temperature distribution

The sensor should represent the actual thermal condition that the control system needs to manage.

Problem 5: Flexible Heaters Solve Integration Challenges

EV battery packs have extremely limited space.

Engineers must fit:

Battery cells
Structural components
Cooling channels
Electrical connections
Sensors
Insulation
Heating elements

This is where flexible heaters become useful.

Unlike rigid heating components, flexible heaters can be customized around the battery structure.

Two common approaches are:

Silicone Rubber Heaters

Silicone heaters are often selected when the design requires:

Larger heating areas
Mechanical durability
Environmental resistance
Flexible installation

Polyimide (PI) Heaters

PI heaters are useful when:

Installation space is limited
Low thickness is important
Weight needs to be minimized
Precise heating areas are required

The correct choice depends on the thermal and mechanical requirements of the battery system.

Problem 6: Battery Heating Is Part of BTMS, Not a Separate Component

Another common mistake is designing the heater independently from the battery thermal management system.

In an EV, heating must work together with:

Battery Management System (BMS)
Temperature sensors
Charging strategy
Cooling system
Vehicle control logic

For example, before fast charging in cold weather, the vehicle may need to precondition the battery.

The heating system needs to bring the battery into a suitable temperature range before higher charging power is available.

The heater is therefore part of the overall energy management strategy.

A Better Engineering Workflow for Battery Heater Design

A more reliable design process is:

Step 1: Define the thermal objective

Determine:

Minimum operating temperature
Target temperature
Required heating time
Acceptable temperature difference

Step 2: Understand the battery structure

Analyze:

Cell arrangement
Module dimensions
Available installation space
Thermal interfaces

Step 3: Design the thermal path

Understand how heat travels from the heater to the cells.

Step 4: Calculate initial power requirements

Estimate required energy and consider heat losses.

Step 5: Select heater construction

Choose the heater type based on:

Thickness requirements
Heating area
Mechanical conditions
Environmental exposure

Step 6: Validate the complete system

Measure:

Heating speed
Temperature distribution
Power consumption
Thermal cycling performance

Testing the complete assembly is more valuable than testing only the heater.

The Main Lesson: A Heater Specification Is Not a Thermal Solution

An EV battery heater is not defined only by:

Voltage
Wattage
Maximum temperature

A successful design depends on the relationship between:

Heat generation → Heat transfer → Heat distribution → Temperature control

The best heater is not necessarily the most powerful one.

It is the heater that fits the battery's thermal architecture.

For engineers working on EV battery heating projects, understanding the complete thermal design process is essential.

A more detailed engineering discussion of EV battery heating system design can be found here:

https://www.fldheaters.com/blog/ev-battery-heating-system-design/

Final Thoughts

As EV battery systems become more compact and energy-dense, thermal management becomes increasingly important.

The future of battery heating is not simply higher power output.

It is smarter integration between:

Heating elements
Thermal interfaces
Sensors
Control systems
Battery structures

Good battery heating design starts with understanding the thermal problem first, then selecting the right heating solution.

2.amazonaws.com/uploads/articles/wwa8h1i36ohkjtv4zt4c.png)

EV Battery Heating System Design: A Practical Engineering Approach

jia yuying — Wed, 14 Oct 2026 06:02:40 +0000

Designing an EV battery heating system is not simply a matter of selecting a heater with enough power.

In cold environments, lithium-ion batteries can experience increased internal resistance, reduced charging performance, lower available power, and slower thermal response. A properly designed heating system needs to address these issues while avoiding excessive energy consumption and temperature gradients across the battery pack.

The key engineering question is:

How can heat be distributed through the battery pack efficiently and uniformly?

This article looks at the main design factors engineers should consider when developing an EV battery heating system.

1. Start With the Battery Thermal Architecture

Before selecting a heater, it is important to understand how heat moves through the battery pack.

A simplified thermal path may look like:

Heater
   ↓
Thermal Interface
   ↓
Cooling Plate / Housing
   ↓
Battery Module
   ↓
Battery Cells

Every layer affects heat transfer.

For example, a heater may have sufficient electrical power but still provide poor heating performance if there is excessive thermal resistance between the heater and battery module.

Important parameters to identify during the initial design stage include:

Battery cell type and dimensions
Module arrangement
Battery pack structure
Cooling plate configuration
Housing materials
Thermal interface materials
Available heater installation area
Ambient temperature
Required warm-up time

This is why heater selection should be part of the overall battery thermal design rather than an isolated component decision.

2. Heater Placement Affects Temperature Distribution

The position of the heater can have a significant effect on the final temperature distribution.

Consider a simple example:

Small high-power heater
        ↓
     HOT SPOT
        ↓
 ───────────────
 |    Battery  |
 ───────────────

The heater may provide enough total energy, but the heat is concentrated in a small area.

A larger heating surface can distribute thermal energy more evenly:

 ┌──────────────────────┐
 │  Distributed Heating │
 │  ██████████████████  │
 │  ██████████████████  │
 └──────────────────────┘
          ↓
   More uniform heating

Depending on the battery architecture, heaters may be installed:

Beneath battery modules
Between thermal plates and modules
On battery enclosure surfaces
Around selected modules
In localized areas requiring additional heat

The optimal position depends on the battery's thermal path, mechanical structure, and available installation space.

3. Heating Uniformity Is as Important as Heating Speed

A battery pack does not necessarily benefit from simply reaching a target temperature as quickly as possible.

Temperature differences between modules or cells also need to be considered.

A system with one hot area and several cold areas may have an acceptable average temperature but still have poor thermal uniformity.

Designers should therefore consider:

Hot spots
Cold zones
Temperature gradients
Module-to-module temperature differences
Heat transfer between the heater and battery

For large and relatively continuous surfaces, flexible silicone heaters can be designed to cover a larger heating area.

For compact areas with limited installation space, thin polyimide heaters can be useful for localized heating.

The important point is that heater material and heater geometry should be selected according to the battery structure.

4. Calculate Thermal Energy Before Selecting Heater Power

A basic thermal-energy calculation can provide a starting point for heater sizing.

The required thermal energy can be approximated by:

Q = m × Cp × ΔT

Where:

Q = required thermal energy
m = battery mass
Cp = specific heat capacity
ΔT = required temperature increase

For example, if a battery system has a large thermal mass, more energy is required to increase its temperature by the same amount.

However, this equation represents an idealized calculation.

Real battery packs also lose heat through:

The enclosure
Cooling structures
Mounting components
Thermal interfaces
Surrounding air
Vehicle structures

Therefore, the actual heater power must account for both the energy required to heat the battery and the heat lost during the process.

5. Look at Watt Density, Not Just Total Wattage

Total heater power alone does not describe how heat will be distributed.

Consider two heaters with the same electrical power:

Heater A
100 W / 0.02 m²

Heater B
100 W / 0.10 m²

Both consume 100 W, but the second heater distributes that energy over a much larger area.

This is why engineers should evaluate:

Power + Heating Area + Watt Density + Thermal Path

A higher watt density may provide faster local heating, but excessive concentration of heat can create temperature gradients.

The design target should therefore balance heating speed with thermal uniformity.

6. Integrate the Heater With Temperature Feedback

An EV battery heater should normally be considered as part of the battery thermal management system.

A simplified control loop might look like:

Temperature Sensor
        ↓
   Control System
        ↓
    Heater ON/OFF
        ↓
 Battery Temperature
        ↓
    Sensor Feedback

A typical sequence could be:

Detect that the battery temperature is below the defined threshold.
Activate the heater.
Monitor battery or module temperature.
Adjust heating according to temperature feedback.
Reduce or stop heating when the required temperature is reached.

This approach can provide better control than applying constant heater power for a fixed amount of time.

The exact control strategy depends on the battery architecture, vehicle control system, operating conditions, and safety requirements.

7. Silicone vs. Polyimide for Battery Heating

The heater construction is another important design decision.

Silicone Rubber Heaters

Silicone rubber heaters are flexible and can be manufactured in custom shapes and dimensions.

They can be useful when the application requires:

Large-area heating
Flexible installation
Custom geometries
Surface heating
Durable insulation
Customized wiring

For example, a battery module with a relatively large flat surface may be suitable for a custom silicone heater.

Polyimide Heaters

Polyimide heaters are particularly useful where installation thickness and available space are limited.

They can be considered for:

Compact modules
Narrow installation gaps
Localized heating
Complex mechanical structures
Thin heating requirements

A simple way to think about the selection is:

Large-area / flexible surface
            ↓
      Silicone Heater

Compact / space-constrained
            ↓
      Polyimide Heater

This is not a universal rule. The final selection should also consider operating temperature, thermal path, mechanical requirements, insulation, mounting method, and environmental conditions.

8. Mechanical Integration Can Change the Thermal Result

A heater can have the correct electrical specifications and still fail to integrate properly into a battery pack.

Before finalizing the design, engineers should check:

Heater dimensions
Surface geometry
Bending requirements
Cable exit position
Connector location
Mounting method
Adhesive selection
Compression
Assembly tolerances
Service access

Cable routing is a simple example.

If the heater cable interferes with a cooling plate or module assembly, the heater may need to be redesigned even if its electrical performance is acceptable.

This is one reason custom heater geometry can be important for OEM battery applications.

9. Thermal Interface Resistance Matters

The heater is only one part of the thermal system.

Suppose a heater is operating correctly, but an air gap exists between the heater and the heated surface.

The electrical input may remain unchanged, but thermal transfer can become less efficient.

Engineers should therefore evaluate:

Surface contact
Thermal interface material
Interface thickness
Thermal conductivity
Air gaps
Mechanical pressure
External insulation

In some cases, improving the thermal interface can provide a better result than simply increasing heater power.

This leads to an important design principle:

Improve the heat path before assuming that more heater power is the solution.

10. Design for Real Operating Conditions

The required heater performance depends strongly on the intended operating environment.

Engineers should consider scenarios such as:

Cold starts
Overnight exposure to low temperatures
Low-temperature charging
Fast charging in cold conditions
Repeated heating and cooling cycles
Different ambient temperatures

A heater that performs well in a controlled laboratory environment may behave differently once it is installed inside a complete battery enclosure.

Testing should therefore consider the complete assembly rather than evaluating the heater alone.

A Practical EV Battery Heater Design Workflow

A useful development process can be summarized as follows.

Step 1: Define the Thermal Requirements

Identify:

Initial temperature
Target temperature
Required warm-up time
Ambient temperature
Allowable temperature difference

Step 2: Understand the Battery Structure

Map the:

Cells
Modules
Cooling plates
Housing
Thermal interfaces
Available heating surfaces

Step 3: Select the Heating Area

Determine whether the design requires:

Full-surface heating
Partial heating
Multiple heating zones
Localized heating

Step 4: Estimate Heater Power

Calculate the approximate thermal energy requirement and account for system heat losses.

Step 5: Evaluate Watt Density

Check whether the selected heating area provides a suitable power distribution.

Step 6: Select Heater Construction

Compare silicone and polyimide based on:

Thickness
Flexibility
Installation space
Heating area
Environmental conditions
Mounting requirements

Step 7: Develop Temperature Control

Integrate temperature sensing and heater control into the battery thermal management architecture.

Step 8: Test the Complete System

Evaluate:

Heater
+ Thermal Interface
+ Battery Module
+ Cooling Structure
+ Enclosure
+ Control System

Testing the complete thermal system provides a more realistic picture of performance than testing the heater alone.

Final Takeaway

The hardest part of EV battery heating system design is not producing heat.

It is delivering the right amount of heat to the right location at the right rate.

A successful design needs to balance:

Heating speed
Temperature uniformity
Watt density
Energy consumption
Thermal interfaces
Mechanical integration
Temperature feedback
Environmental durability

For large-area battery surfaces, flexible silicone heaters can provide a practical approach to distributed heating. For compact or space-constrained applications, thin polyimide heaters can provide additional installation flexibility.

The final heater design should be developed around the battery architecture rather than treating the heater as an independent component.

For engineers working on an EV battery heating project, the most useful starting point is therefore not:

“How many watts do I need?”

It is:

“Where does the heat need to go, how quickly does it need to get there, and how evenly does it need to be distributed?”

EV Battery Heating System Design: A Practical Engineering Approach

jia yuying — Tue, 29 Sep 2026 07:37:37 +0000

Designing an EV battery heating system is not simply a matter of selecting a heater with enough power.

The key engineering question is:

How can heat be distributed through the battery pack efficiently and uniformly?

This article looks at the main design factors engineers should consider when developing an EV battery heating system.

1. Start With the Battery Thermal Architecture

Before selecting a heater, it is important to understand how heat moves through the battery pack.

A simplified thermal path may look like:

Heater
   ↓
Thermal Interface
   ↓
Cooling Plate / Housing
   ↓
Battery Module
   ↓
Battery Cells

Every layer affects heat transfer.

For example, a heater may have sufficient electrical power but still provide poor heating performance if there is excessive thermal resistance between the heater and battery module.

Important parameters to identify during the initial design stage include:

Battery cell type and dimensions
Module arrangement
Battery pack structure
Cooling plate configuration
Housing materials
Thermal interface materials
Available heater installation area
Ambient temperature
Required warm-up time

This is why heater selection should be part of the overall battery thermal design rather than an isolated component decision.

2. Heater Placement Affects Temperature Distribution

The position of the heater can have a significant effect on the final temperature distribution.

Consider a simple example:

Small high-power heater
        ↓
     HOT SPOT
        ↓
 ───────────────
 |    Battery  |
 ───────────────

The heater may provide enough total energy, but the heat is concentrated in a small area.

A larger heating surface can distribute thermal energy more evenly:

 ┌──────────────────────┐
 │  Distributed Heating │
 │  ██████████████████  │
 │  ██████████████████  │
 └──────────────────────┘
          ↓
   More uniform heating

Depending on the battery architecture, heaters may be installed:

Beneath battery modules
Between thermal plates and modules
On battery enclosure surfaces
Around selected modules
In localized areas requiring additional heat

The optimal position depends on the battery's thermal path, mechanical structure, and available installation space.

3. Heating Uniformity Is as Important as Heating Speed

A battery pack does not necessarily benefit from simply reaching a target temperature as quickly as possible.

Temperature differences between modules or cells also need to be considered.

A system with one hot area and several cold areas may have an acceptable average temperature but still have poor thermal uniformity.

Designers should therefore consider:

Hot spots
Cold zones
Temperature gradients
Module-to-module temperature differences
Heat transfer between the heater and battery

For large and relatively continuous surfaces, flexible silicone heaters can be designed to cover a larger heating area.

For compact areas with limited installation space, thin polyimide heaters can be useful for localized heating.

The important point is that heater material and heater geometry should be selected according to the battery structure.

4. Calcu

EV Battery Heating: Why Heater Power Is Only Part of the Problem

jia yuying — Wed, 23 Sep 2026 02:23:13 +0000

Cold temperatures can change the thermal behavior of lithium-ion batteries significantly.

For EVs operating in cold climates, battery heating may be required before charging or high-power operation. A common approach is to add a flexible heater to the battery module.

But there is an easy mistake to make:

Choosing the heater based only on its wattage.

A 200 W heater does not automatically provide better battery heating than a 150 W heater. The actual result depends on how that heat is distributed and transferred.

1. Heat Distribution Matters

Imagine a battery module heated from underneath.

If most of the heater's power is concentrated in a small area, the surface above the heater can become much warmer than the rest of the module.

The average temperature may look acceptable, while significant temperature differences remain.

For battery heating, engineers should therefore consider:

Heating area
Power density
Heater layout
Thermal contact
Insulation
Sensor position

The goal is not simply to generate more heat. It is to deliver the right amount of heat to the right areas.

2. Thermal Contact Can Change the Result

Heat needs a path from the heating element to the battery.

An air gap or poor mounting interface can increase thermal resistance and slow down heat transfer.

This is one reason flexible silicone heaters can be useful in battery applications. Their construction allows the heater to conform to the target surface and be customized around the available installation area.

But the heater material alone is not enough. The mounting method and thermal interface also need to be considered.

3. Sensor Position Is Part of the Design

A temperature sensor only measures the temperature where it is installed.

If the sensor is too close to the heater, it may detect a local temperature increase while other areas of the battery are still cold.

If it is too far away, the control response may become slower.

This means the heater and temperature sensor should be designed together.

A simple way to view the system is:

Battery → Thermal Interface → Heater → Sensor → Controller/BMS

Changing one part can affect the behavior of the entire system.

4. Flexible Heaters Need to Match the Battery Structure

EV battery modules contain cells, cooling components, busbars, sensors, wiring, and structural parts.

The available space for a heater is therefore often limited.

A customized silicone heater can be designed around requirements such as:

Length and width
Heater shape
Voltage
Power
Resistance
Lead-wire position
Mounting method

This makes flexible heaters particularly useful when a standard heating pad cannot match the battery geometry.

A Better Starting Point

Instead of asking:

“How many watts should the heater have?”

Start with:

“Where does the battery need heat, how quickly does it need to reach the target temperature, and how evenly should the heat be distributed?”

Once those requirements are clear, heater power, geometry, sensor position, and mounting method can be designed around the actual thermal problem.

For a more detailed discussion of silicone heater design for EV battery applications, see the full engineering article on FLD's website.

EV #Battery #ThermalManagement #BatteryHeating #ElectricVehicles #Engineering

Preventing Condensation in Outdoor EV Charging Enclosures: A Practical Thermal Design Approach

jia yuying — Tue, 22 Sep 2026 07:24:21 +0000

Outdoor EV charging equipment has to deal with more than low ambient temperatures.

A charging enclosure can experience large temperature swings between day and night, changing humidity conditions, rain, snow, and repeated heating and cooling cycles. Under the right conditions, moisture can condense on internal surfaces even when the enclosure itself is properly sealed.

For engineers designing outdoor charging equipment, this creates an interesting thermal problem:

How do you keep sensitive surfaces above the condensation point without unnecessarily heating the entire enclosure?

One practical approach is localized thermal management.

Why Condensation Happens Inside a Sealed Enclosure

A sealed enclosure does not necessarily mean a dry enclosure.

Suppose an outdoor charging cabinet contains air at a relatively high humidity level. During operation, the internal air may be warmer than the surrounding environment.

When the equipment is shut down, the internal temperature can gradually fall.

If a component surface becomes colder than the surrounding air's dew point, water vapor can condense on that surface.

The basic relationship is:

Surface temperature < Dew point → Condensation risk

This is particularly important for components with relatively high thermal conductivity or direct thermal paths to the outside of the enclosure.

Examples include:

Metal mounting plates
Connectors
Cable terminals
Heat sinks
Display windows
Sensor housings
Exposed electronic components

The problem is therefore not simply "the cabinet is too cold."

It is often:

a specific surface is colder than the surrounding environment.

That distinction changes how the heating system should be designed.

Think About Surface Temperature, Not Just Air Temperature

A common design approach is to measure the air temperature inside the enclosure and activate a heater when the temperature drops below a predefined value.

This can work, but it has an important limitation.

Air temperature and component surface temperature are not always the same.

For example, a metal surface connected to the outside of the enclosure may cool much faster than the internal air.

This creates a thermal gradient:

Outside air
    ↓
Enclosure wall
    ↓
Metal mounting structure
    ↓
Electronic component

Even if the internal air remains above a certain temperature, a colder surface can still approach the dew point.

For condensation prevention, it is therefore useful to consider three variables:

Ambient temperature

How cold is the environment?

Relative humidity

How much moisture is present in the air?

Critical surface temperature

How cold can the protected component become?

The heater control strategy should ideally consider the relationship between these variables rather than relying on a single temperature threshold.

Dew Point Is a More Useful Reference

Relative humidity alone does not tell you when condensation will occur.

Dew point provides a more practical reference.

For engineering calculations, a commonly used approximation is the Magnus equation:

γ(T,RH) = ln(RH/100) + aT/(b+T)

Td = bγ/(a-γ)

Where:

T = air temperature
RH = relative humidity
Td = dew-point temperature
a and b = empirical constants

The exact calculation method can vary, but the design principle is straightforward:

Keep the critical surface temperature sufficiently above the dew point.

This changes the heating requirement considerably.

You may not need to heat an entire charging enclosure from 0°C to 20°C.

You may only need to prevent several critical surfaces from falling below a safe temperature margin.

That is where localized heating becomes attractive.

Why Localized Heating Can Be More Efficient

Consider two different strategies.

Strategy A: Heat the Entire Enclosure

A large heater raises the temperature of the internal air.

The advantage is simplicity.

The disadvantage is that much of the energy may be used to heat components that do not actually need protection.

The enclosure also loses heat through its walls, ventilation paths, cable openings, and structural components.

Strategy B: Heat Critical Surfaces

Instead of heating the entire enclosure, heating elements are placed near condensation-sensitive areas.

For example:

+--------------------------------+
|        Charging Enclosure      |
|                                |
|   [Control Board]              |
|        ↑ Heater                |
|                                |
|   [Connector] ← Heater         |
|                                |
|   [Display Window] ← Heater    |
|                                |
+--------------------------------+

The objective is to maintain the temperature of these surfaces rather than raise the temperature of the entire enclosure.

This approach can reduce the required thermal mass and potentially reduce energy consumption.

However, the heater must be designed around the actual thermal path of the component.

Heater Placement Matters

Installing a heater inside an enclosure is not automatically effective.

The location of the heater determines how efficiently heat reaches the target surface.

For example, placing a heater several centimeters away from a metal component may result in significant heat loss to the surrounding air.

A heater attached directly to the target surface can provide a more predictable conduction path.

This is one reason thin flexible heaters are useful for certain charging equipment designs.

They can conform to irregular surfaces and occupy relatively little installation space.

Typical targets may include:

Metal plates
Small control areas
Display assemblies
Connector regions
Sensor mounting areas
Enclosure sections prone to condensation

The exact configuration depends on the thermal structure of the charging equipment.

Sensor Location Is Just as Important

The heater itself is only one part of the system.

The sensor position can determine whether the control strategy works correctly.

Imagine a temperature sensor installed close to the heater:

Heater → Sensor

The sensor may quickly reach the target temperature even though the protected surface farther away remains too cold.

The controller then switches the heater off.

This can create a false sense of thermal protection.

A better approach is to place the sensor where it represents the temperature of the critical area as closely as practical.

Depending on the design, this could mean:

Near the coldest surface
On the protected component
Near a thermal bridge
At a representative location inside the enclosure

For more advanced systems, temperature and humidity sensors can be combined to estimate condensation risk.

Do Not Overlook Thermal Bridges

Thermal bridges are another important source of cold spots.

A metal bracket, mounting screw, cable gland, or structural connection can provide a relatively low-resistance thermal path between the internal components and the outdoor environment.

The result can look like this:

Warm internal area
        |
        |
   Electronic board
        |
   Metal bracket
        |
   Enclosure wall
        |
   Cold outdoor air

The bracket may become significantly colder than the surrounding enclosure.

If a sensitive component is connected to that structure, condensation risk can increase locally.

In these situations, thermal insulation and localized heating may need to be considered together.

Heating alone does not always solve the underlying thermal path.

A Simple Engineering Workflow

A practical design process can start with the following steps.

1. Define the Environmental Conditions

Identify:

Minimum ambient temperature
Maximum ambient temperature
Expected relative humidity
Rain, snow, and condensation exposure
Temperature cycling conditions

2. Identify Critical Components

Determine which parts are sensitive to moisture or frost.

Do not automatically treat every component as equally important.

3. Determine the Critical Surface Temperature

Measure or estimate the temperature of the surfaces most likely to become cold.

This can be more useful than looking only at enclosure air temperature.

4. Estimate the Dew Point

Use temperature and humidity data to establish the condensation threshold.

5. Establish a Temperature Margin

Instead of designing the heater to operate exactly at the dew point, introduce a suitable engineering margin based on the application and environmental uncertainty.

6. Select the Heating Method

Possible approaches include:

Enclosure air heating
Surface heating
Insulation
Passive thermal design
A combination of these methods

7. Validate Under Cycling Conditions

A heater that works under a constant low temperature may behave differently during repeated heating and cooling cycles.

Testing should consider:

Startup
Shutdown
Rapid temperature changes
High humidity
Frost conditions
Long-duration operation

Where Flexible Heaters Fit

Flexible heaters are one possible solution when the protected surface has limited installation space or an irregular geometry.

Silicone rubber heaters and polyimide heaters are commonly considered for applications where a thin, conformable heating element is needed.

The important point is that the heater should be treated as part of the thermal system rather than as an isolated component.

The engineering question is not simply:

"What wattage heater should I use?"

It is:

"Where does the heat need to go, and what surface temperature must be maintained?"

That shift in thinking usually leads to a more controlled design.

Final Takeaway

Condensation protection in outdoor EV charging equipment is fundamentally a thermal-management problem.

The most important variables are not just ambient temperature and heater power.

Engineers should consider:

Dew point
Critical surface temperature
Relative humidity
Thermal bridges
Heat-transfer paths
Sensor position
Heater placement
Temperature control
Environmental cycling

For some designs, heating the entire enclosure may be appropriate.

For others, protecting a few condensation-sensitive surfaces with localized heating can provide a more targeted approach.

The best solution depends on the enclosure structure, environmental conditions, component layout, and required operating temperature.

In other words, good condensation control starts with understanding the thermal path—not simply adding more heat.

EV Battery Heating Problems: Why More Heater Power Does Not Always Mean Better Heating

jia yuying — Mon, 21 Sep 2026 06:15:17 +0000

When an EV battery heater does not bring the battery up to temperature as expected, the first thing that often gets checked is power.

If the heater is rated at 100 W, the assumption is that increasing it to 150 W or 200 W should solve the problem.

Sometimes it does.

But in battery heating applications, simply increasing heater power can also create a different problem: the heater gets hot, while the battery does not heat evenly.

This usually means the problem is not the total power alone. It is related to where the heat is being generated, how it is transferred, and how the temperature is being measured.

Here is a practical way to look at the problem.

Start With the Heating Area

Suppose a battery module has a relatively large flat surface, but the heater covers only part of it.

The heater may still have enough total wattage to generate the required amount of heat. However, the area directly above the heater will receive heat much faster than areas outside the heating zone.

This creates a temperature gradient.

For battery applications, it is often more useful to look at power per unit area rather than total wattage alone.

For example, two heaters may both be rated at 100 W:

Heater A: 100 W over 0.05 m²
Heater B: 100 W over 0.10 m²

They have the same total power, but their heat distribution is not the same.

The second heater spreads the same energy over a larger surface.

That does not automatically make it the correct solution, but it illustrates why heater area needs to be considered together with power.

When designing a battery heater, I would normally start with the required heating area and thermal target before deciding the final wattage.

Check the Thermal Path, Not Just the Heater

Another common source of problems is the thermal interface between the heater and the battery.

A heater can produce the specified electrical power while transferring less heat than expected to the battery.

For example, if there is an air gap between the heater and the battery surface, the thermal resistance can become significant.

The result is easy to recognize:

The heater temperature rises quickly, but the battery temperature responds slowly.

This is why the mechanical installation of the heater matters almost as much as its electrical specification.

Depending on the battery structure, engineers may need to consider:

Surface flatness
Contact pressure
Thermal interface materials
Adhesive thickness
Mounting method
Air gaps
Mechanical tolerances

A flexible heater works best when its heating surface has a predictable thermal path into the component being heated.

More Power Can Create a Hot Spot

Increasing heater power can be useful when the heating time is too long.

But there is a limit.

If the heater is already concentrated over a relatively small area, increasing its power density can raise the heater temperature much faster than the rest of the battery.

This is particularly important for battery modules because the desired result is normally not "make the heater hot."

The desired result is to bring the battery to the required temperature range in a controlled way.

That distinction changes the design approach.

Instead of asking:

How many watts do we need?

It is often better to ask:

How much heat needs to reach the battery, over what area, and within what time?

The answer can lead to a different heater geometry rather than simply a higher wattage.

Temperature Sensor Location Can Mislead the Control System

I have also seen temperature-control problems that are actually sensor-location problems.

Imagine the heater is installed close to one side of a battery module and the temperature sensor is placed several centimeters away.

The sensor may show a relatively low temperature while the area around the heater is already much warmer.

The controller continues supplying power because the sensor has not reached its target temperature.

This can cause unnecessary heating and a larger temperature difference across the module.

The opposite situation can happen as well.

If the sensor is located too close to the heater, it may reach the target temperature quickly and shut the heater down while the rest of the battery is still cold.

So the sensor should be considered as part of the heater design.

It is not simply an electrical accessory that can be added at the end.

For some battery applications, NTC sensors or other temperature-sensing components can be integrated into the heating assembly according to the control requirements.

Silicone or PI? Start With the Mechanical Design

The choice of heater material is another area where specifications can be misleading.

Silicone rubber heaters and polyimide (PI) heaters can both be used for battery heating, but they solve somewhat different integration problems.

A silicone heater is useful when the application requires a flexible heating surface with a customized shape and relatively large heating area.

A PI heater is extremely thin and can be useful where available installation space is limited.

The better question is therefore not:

Which heater material is better?

The more useful engineering question is:

Which heater construction fits the battery geometry and thermal interface?

For example, if there is very little clearance between components, heater thickness may become more important than maximum operating temperature.

If the heater needs to cover a larger irregular surface, flexibility and customized geometry may become more important.

The battery structure should drive the heater selection.

Calculate the Heating Requirement Before Selecting the Heater

For a first-order estimate, the energy required to raise the temperature of a mass can be approximated by:

Q = m × Cp × ΔT

Where:

Q = required thermal energy
m = mass of the battery or component
Cp = specific heat capacity
ΔT = required temperature increase

If the heating needs to happen within a specific time:

P ≈ Q / t

This gives a starting point for estimating heating power.

However, this is not the final heater rating.

Real systems have heat losses through the battery housing, cooling structure, mounting components, surrounding air, and other paths.

The actual design therefore needs to account for the thermal environment and the efficiency of heat transfer.

This is one reason prototype testing remains important even when the initial thermal calculation looks correct.

Do Not Forget the Cooling System

A battery heater can also interact with the vehicle's existing cooling architecture.

For example, a battery pack may use liquid cooling during normal operation. The heating strategy may need to warm the battery before the cooling loop becomes active, or the system may need to coordinate heating and cooling depending on operating conditions.

The heater therefore should not be designed as an isolated component.

The control logic needs to consider:

Battery temperature
Ambient temperature
Charging status
Vehicle operating condition
Heating power
Cooling availability
Temperature limits

This is particularly important during battery preconditioning.

Heating and cooling are different functions, but they are part of the same thermal management system.

I discussed this system-level relationship in more detail here:

EV Battery Thermal Management: How Cooling and Heating Work Together

A Practical Troubleshooting Sequence

If an EV battery heater is not producing the expected result, I would not immediately replace it with a higher-power version.

A more useful troubleshooting sequence is:

Verify the actual electrical input

Check voltage, current, resistance, and actual power rather than relying only on the heater label.

Check the heating area

Confirm that the active heating area matches the battery area that actually needs to be heated.

Measure the heater surface temperature

Compare heater temperature with battery surface temperature.

A large difference can indicate a thermal-transfer problem.

Check the mechanical interface

Look for air gaps, poor contact, uneven pressure, or excessive adhesive thickness.

Check sensor placement

Compare the sensor reading with measurements at several points across the battery surface.

Review the power density

If the heater surface is getting hot very quickly, increasing wattage may make the temperature distribution worse.

Review the control strategy

Check when heating starts, when it stops, and whether cooling or other thermal systems are operating at the same time.

This approach usually gives more useful information than changing heater wattage first.

Design the Heater Around the Battery

One of the biggest differences between a general-purpose heater and an EV battery heater is the level of integration required.

The heater needs to fit the actual battery structure.

That can mean customizing:

Length and width
Shape
Heating zones
Voltage
Resistance
Power
Lead-wire position
Sensor location
Thickness
Mounting method

For OEM battery projects, the heater is often developed alongside the mechanical and thermal design rather than selected as an off-the-shelf component.

That approach also makes it easier to test the complete thermal path instead of testing the heater by itself.

Final Takeaway

When an EV battery heater is not performing as expected, higher wattage is only one possible solution.

In many cases, the real issue is related to heating area, power density, thermal contact, sensor placement, or control strategy.

The most useful starting point is to look at the complete thermal path:

Electrical power → heater → thermal interface → battery structure → temperature sensor → control system

If one part of that chain is poorly designed, increasing heater power may not solve the underlying problem.

For engineers working on EV battery thermal management, heater design should therefore begin with the battery's thermal and mechanical requirements rather than with a standard heater specification.

For more information on customized battery heating applications, see the EV battery heating solutions from Fulianda.

Designing Polyimide Heaters for Compact Electronic Devices

jia yuying — Thu, 17 Sep 2026 06:58:03 +0000

In compact electronics, adding a heater is rarely just a matter of choosing a wattage.

A battery may need to be warmed in a cold environment. A camera lens may need to stay above the condensation point. An optical sensor may require localized temperature stabilization.

These applications have one thing in common:

The heater is part of the thermal design of the device, not an independent component.

Polyimide (PI) film heaters are particularly useful when the available installation space is limited and heat needs to be delivered to a specific component.

Start With the Thermal Target

A common mistake is to start heater selection with voltage and wattage.

A better starting point is:

What component needs to reach what temperature, under what environmental conditions?

For example:

Battery → raise cell temperature before low-temperature operation
Camera lens → maintain the optical surface above the condensation threshold
Sensor → stabilize the local operating temperature
Display → provide controlled temperature compensation
Electronic enclosure → reduce condensation during temperature cycling

The same 10 W heater can behave very differently depending on its mounting position, contact area, thermal mass, and heat-loss path.

Heater Placement Can Matter More Than Heater Power

Consider a camera lens.

If the heater is mounted several millimeters away from the optical surface, increasing heater power may not efficiently solve the problem. Heat can be lost through the housing before reaching the lens.

The same principle applies to battery packs and sensors.

A practical thermal design should evaluate:

Contact area
Thermal interface
Mounting surface
Heat conduction path
Surrounding materials
Thermal insulation
Ambient temperature
Heat dissipation

This is why localized heating is often more effective than simply increasing total heater power.

Why PI Heaters Fit Compact Electronics

Polyimide heaters use a thin-film construction that can be customized to fit restricted installation areas.

They can be designed with:

Custom length and width
Irregular outlines
Cutouts
Different lead-wire positions
Custom voltage and resistance
Sensor integration
Adhesive mounting

This makes them useful for applications where a conventional rigid heating element would consume too much space.

Typical applications include:

Battery Heating

For battery systems, the heater can be positioned close to the cell or module to improve heat transfer.

The design needs to account for battery dimensions, allowable temperature range, thermal path, heating time, and available electrical power.

The heater should also be integrated with the battery's temperature monitoring and control strategy rather than operated independently.

Camera Lens Heating

For outdoor cameras, the thermal target is often the lens or optical window rather than the entire camera.

A thin PI heater can be designed around the optical assembly to provide localized heat and reduce condensation or frost formation.

The important parameters include lens geometry, heater position, ambient temperature, humidity, and heat loss through the camera housing.

Optical Sensors

Optical sensors can be affected by both temperature variation and condensation.

A localized heater can maintain the temperature of the optical surface without unnecessarily heating the complete sensor assembly.

This is particularly useful for outdoor imaging and measurement equipment.

PI Heater vs. Silicone Heater

PI is not automatically the correct choice for every electronic device.

The mechanical and thermal requirements should determine the heater construction.

Requirement	PI Heater	Silicone Heater
Very limited space	Suitable	Less suitable in some designs
Thin construction	Strong advantage	Available, but generally thicker
Small optical assembly	Suitable	Possible
Irregular/curved surface	Suitable	Suitable
Larger heating area	Application dependent	Often practical
Flexible enclosure heating	Possible	Often preferred

For a compact optical component, PI may provide a better integration path.

For a larger enclosure or surface requiring flexible coverage, silicone rubber heaters may be more practical.

Temperature Control Should Be Designed With the Heater

A heater does not necessarily need to operate continuously at full power.

Depending on the application, temperature feedback can be provided by:

NTC thermistors
RTD sensors
Thermostats
External temperature controllers

For example, a camera heater can be controlled according to the local temperature or environmental conditions instead of remaining continuously energized.

This approach can reduce unnecessary power consumption and help prevent excessive local temperature rise.

A Simple Engineering Workflow

For OEM electronic products, I recommend defining the thermal problem in this order:

1. Identify the target component

What actually needs to be heated?

2. Define the temperature requirement

What is the minimum and maximum required temperature?

3. Define the environment

Consider ambient temperature, humidity, airflow and expected temperature cycling.

4. Map the heat path

Determine how heat will move from the heater to the target component.

5. Define the mechanical constraints

Available thickness, installation area, bends, cutouts, wires and connectors all affect the heater design.

6. Determine electrical requirements

Voltage, resistance and power should be selected after understanding the thermal requirements.

7. Add temperature control

Determine whether NTC, RTD, thermostat or another control method is required.

This workflow generally produces a more reliable design than selecting a standard heater based only on wattage.

The Main Design Principle

For compact electronics, the most important question is not:

"How powerful should the heater be?"

It is:

"How efficiently can the required heat be delivered to the component that actually needs it?"

That distinction becomes important as electronic products become smaller and thermal margins become tighter.

For OEM applications, PI heaters can be customized around the mechanical structure of the product, including dimensions, shape, voltage, resistance, power, lead location and sensor position.

FLD develops customized PI and silicone heating elements for batteries, cameras, optical equipment, sensors and other electronic devices.

Technical reference:
https://www.fldheaters.com/product/Polyimideheaters.html

Custom heater inquiry:
https://www.fldheaters.com/Contact.html

Silicone vs. PI Heaters for EV Battery Modules: The Design Constraints That Matter

jia yuying — Tue, 15 Sep 2026 06:53:38 +0000

When designing a heating system for an EV battery module, the first question is often:

Should we use a silicone heater or a polyimide (PI) heater?

In practice, that question is too broad.

Both technologies can provide flexible surface heating, but the better choice usually depends on the mechanical and thermal constraints of the battery module.

For engineers, the more useful approach is to start with the battery architecture and work backward to the heater design.

Start With the Installation Space

Battery modules are already highly constrained assemblies.

Cells, busbars, cooling components, insulation, sensors and structural parts all compete for limited space. Adding a heater means introducing another layer into this stack-up.

This makes heater thickness more important than it may initially appear.

A heater can meet the required voltage, power and temperature specifications but still be unsuitable if there is not enough clearance for installation.

This is one area where PI heaters can be particularly useful.

Their thin construction allows the heating element to be integrated into compact areas where a thicker heater may create mechanical interference.

For larger battery surfaces with fewer space restrictions, silicone heaters may provide a more practical solution.

Heating Area Matters More Than Total Wattage

Another common approach is to select a heater based primarily on wattage.

That can be misleading.

Suppose two heaters both provide 100 W. If one distributes the heat over a much larger surface while the other concentrates the power into a smaller area, the thermal behavior of the battery module can be very different.

The actual design should therefore consider:

Heating area
Power density
Surface contact
Heat transfer path
Battery mass
Initial temperature
Target temperature
Heat loss

The objective is not simply to generate more heat.

The objective is to deliver the required amount of heat to the right location with acceptable temperature distribution.

This is particularly important for battery modules where localized heating can create temperature differences between different areas.

Silicone Heaters: Where They Fit

Silicone rubber heaters are well suited to applications where the heating element needs to conform to a battery surface.

They can be manufactured in custom shapes and sizes, making them useful when the available heating area is not a simple rectangle.

A silicone heater can make sense when the design requires:

A relatively large heating area
Flexible surface contact
Custom geometry
Robust mechanical integration
Space for the heating element

For example, a battery module with a broad accessible surface may allow the heater to cover a larger portion of the module.

In this situation, the ability to customize the heater geometry can be more valuable than minimizing thickness alone.

PI Heaters: Where They Fit

Polyimide heaters are particularly attractive when space and thickness are critical.

A compact battery assembly may have only a small gap available for the heating element. In such cases, reducing heater thickness can simplify mechanical integration.

PI heaters can also be customized for different dimensions, resistance values, voltage requirements and lead configurations.

The main engineering advantage is therefore not simply that PI is a different heating material.

It is that the heater can be designed as a thin component within a constrained assembly.

A Practical Comparison

Design Factor	Silicone Heater	PI Heater
Large heating surface	Strong choice	Suitable
Limited installation space	Suitable	Strong choice
Thin construction	Good	Excellent
Lightweight design	Good	Excellent
Flexible mounting	Excellent	Excellent
Custom geometry	Excellent	Excellent
Compact battery modules	Good	Strong choice
Larger battery surfaces	Strong choice	Good

This is not a specification ranking.

It is a way to identify which technology should be evaluated first based on the mechanical requirements of the battery.

Don't Ignore the Mounting Method

The heater itself is only one part of the thermal path.

The interface between the heater and battery surface can significantly affect heat transfer.

If the heater does not maintain consistent contact with the target surface, part of the generated heat may be lost through unwanted thermal paths.

The mounting design should therefore be considered together with:

Surface flatness
Adhesive or mounting method
Compression
Thermal interface materials
Mechanical tolerances
Vibration
Thermal cycling

For a production battery module, the heater should be treated as part of the mechanical assembly rather than as an independent electrical component.

Temperature Control Is a System-Level Problem

A heater that produces a fixed amount of power does not automatically maintain a fixed temperature.

Actual heater temperature depends on the thermal environment.

For this reason, battery heating systems normally need some form of temperature monitoring and control.

The design may include a temperature sensor such as an NTC or another suitable sensor, together with a controller or power-management system.

Sensor placement matters as well.

If the sensor is located far from the actual heating zone, the measured temperature may not represent the temperature that the control system needs to regulate.

This can lead to unnecessary heating or insufficient heating.

How I Would Approach Heater Selection

Instead of starting with a product catalog, I would define the application in this order:

1. Define the thermal target

What part of the battery actually needs to be heated?

2. Define the available space

Measure the maximum allowable heater thickness, width and length.

3. Define the heating time

Determine how quickly the battery needs to reach the target temperature.

4. Estimate the required power

Consider battery mass, starting temperature, target temperature and heat loss.

5. Select the heater construction

At this stage, silicone and PI can be compared based on the actual mechanical constraints.

6. Design the control system

Determine sensor location, temperature limits and power-control strategy.

This sequence prevents the heater material from becoming the starting point of the design when the real limitation may be mechanical clearance or thermal distribution.

The Real Selection Criteria

For EV battery applications, I would summarize the decision this way:

Silicone becomes attractive when surface coverage, flexibility and mechanical integration are the priority.

PI becomes attractive when thickness, weight and installation space are the main constraints.

Neither technology is automatically better.

The better solution is the one that fits the battery's thermal and mechanical architecture.

Final Thoughts

Flexible battery heaters are relatively simple electrical components, but integrating them into a battery system is not always simple.

The heater has to work within a limited mechanical envelope while delivering predictable heat to the required area.

That is why parameters such as heater thickness, heating area, power density, mounting and temperature sensing should be considered together.

If you are evaluating silicone or PI heating technology for an EV battery module, it is useful to define the battery dimensions, available installation space, voltage, required power, target temperature and heating time before selecting the heater construction.

For more information on flexible heating for EV battery applications, see Fulianda's EV Battery Heating Solutions.

What constraints have you found most difficult when integrating a heater into a battery module — thickness, heat distribution, mounting, or temperature control?

Designing Heaters for Semiconductor Equipment: An Engineer’s Approach to Thermal Stability

jia yuying — Thu, 10 Sep 2026 02:43:30 +0000

When designing thermal systems for semiconductor equipment, one of the first mistakes engineers can make is to think of the heater as simply a source of heat.

In practice, the difficult part is usually not generating enough thermal power. The challenge is delivering that heat uniformly, predictably, and within the physical constraints of the equipment.

A heater that reaches the target temperature quickly can still create process problems if one area becomes significantly hotter than another. Likewise, a heater with good thermal performance may not be practical if it cannot fit around a chamber, valve, pipeline, or other constrained component.

This is why flexible heaters are increasingly useful in semiconductor equipment where conventional heating elements are difficult to integrate.

The Real Engineering Problem: Controlling Heat Where It Is Needed

A semiconductor process may involve chambers, gas delivery lines, valves, fittings, sensors, and other components that operate under very different thermal conditions.

From an engineering perspective, I would normally look at four questions first:

Where does heat need to be maintained?
What temperature range is required?
How uniform does the temperature need to be?
How can the heater physically be integrated into the equipment?

These questions are more important than simply selecting a heater based on wattage.

For example, increasing heater power can shorten warm-up time, but excessive localized power density may create hot spots. A better solution may be to redesign the heating pattern and distribute the power across the required surface.

Temperature Uniformity Is Often More Important Than Maximum Temperature

Many semiconductor processes operate within relatively narrow thermal windows.

A chamber surface, gas line, or valve may technically reach the required temperature, but temperature differences across the component can still affect process consistency.

Potential problems include:

thermal gradients
localized condensation
precursor deposition
process drift
inconsistent material behavior
increased maintenance requirements

For this reason, heater geometry and power distribution should be considered together.

A flexible heater can be designed around the actual component geometry rather than forcing the equipment to accommodate a standard heater shape.

Why Installation Geometry Matters

Semiconductor equipment often has very limited installation space.

There may be cables, sensors, mechanical structures, vacuum components, and other assemblies competing for the same space.

A traditional rigid heater may therefore create several problems:

insufficient contact with the surface
excessive thickness
difficult installation
interference with nearby components
uneven thermal transfer

Flexible heaters offer a different approach.

Silicone rubber heaters can conform to curved or irregular surfaces, while polyimide heaters are useful when a thin and lightweight heating structure is required.

The heater can also be manufactured with customized dimensions, openings, lead positions, resistance values, and sensor configurations.

From a mechanical design perspective, this is important because the heater becomes part of the component design rather than an external accessory added afterward.

Gas Lines and Valves Need More Than Simple Heating

Gas delivery systems are another area where thermal control becomes important.

If a process gas or precursor travels through a line that is colder than the required operating temperature, condensation or deposition can occur.

This can affect:

gas flow consistency
line cleanliness
process repeatability
maintenance intervals

Valves and fittings can present similar problems because their geometry can create localized heat-loss areas.

In these applications, the objective is not necessarily to make the entire system extremely hot. The objective is to maintain the required thermal condition along the critical path.

That means heater placement and temperature feedback are just as important as heater output.

Temperature Sensors Should Be Considered During Heater Design

Another common engineering consideration is temperature feedback.

A heater can be designed to produce a specific amount of power, but without reliable temperature measurement, the actual surface temperature may vary with ambient conditions, mounting methods, airflow, and heat dissipation.

Depending on the application, engineers may integrate:

RTD sensors
thermocouples
NTC sensors

The sensor location is particularly important.

Placing the sensor too far from the critical heating area may result in a temperature reading that does not accurately represent the actual process surface.

Therefore, heater layout and sensor position should ideally be designed together.

Power Density Is a Design Parameter, Not Just Total Wattage

Two heaters can have the same total power but produce very different thermal results.

For example:

Heater A

400 W concentrated over a relatively small area

Heater B

400 W distributed over a larger and more carefully designed heating pattern

The total power is identical, but the surface temperature distribution can be very different.

This is why semiconductor heater design should consider power density distribution rather than total wattage alone.

The heating pattern can be adjusted to compensate for areas with higher heat loss or different thermal characteristics.

Flexible Heaters Can Simplify Prototype Development

Semiconductor equipment manufacturers frequently work with customized mechanical structures.

During development, dimensions may change several times before the final equipment configuration is established.

A flexible heater can be modified to match the updated geometry without completely redesigning the surrounding equipment.

A typical development process may look like this:

Equipment Geometry → Heater Layout → Prototype → Temperature Testing → Design Optimization → Production

Temperature mapping during prototype testing is especially useful.

It can reveal hot spots, cold areas, insufficient contact, or unexpected heat loss that may not be obvious from theoretical calculations.

What I Would Check Before Specifying a Heater

When evaluating a heater for semiconductor equipment, I would normally collect the following information first:

Mechanical Requirements

Heating area
Component dimensions
Surface shape
Available installation space
Mounting method
Cable exit location

Electrical Requirements

Operating voltage
Required wattage
Resistance
Power density
Control method

Thermal Requirements

Target temperature
Temperature tolerance
Warm-up time
Required uniformity
Heat-loss conditions

Environmental Requirements

Vacuum exposure
Chemical exposure
Ambient temperature
Continuous or intermittent operation
Cleaning requirements

These parameters provide a much better starting point than selecting a heater based only on its nominal temperature rating.

Choosing Between Silicone and Polyimide Heaters

The heater material should also be selected according to the application.

Silicone rubber heaters are useful when flexibility, mechanical durability, and conformity to irregular surfaces are important.

Polyimide heaters are particularly attractive when the design requires a thin heating structure, low mass, and limited installation space.

The final selection depends on the actual operating environment rather than simply choosing the material with the highest temperature rating.

The Heater Should Be Designed With the Equipment

One lesson from thermal integration is that heater selection should not happen at the very end of equipment development.

If heating is considered early, engineers can optimize:

heater geometry
sensor location
mounting method
cable routing
power distribution
thermal insulation

This can reduce redesign work later in the project.

For equipment manufacturers working on customized thermal requirements, the overall approach to [semiconductor equipment heater design]should therefore start with the component geometry and process requirements rather than with a standard heater model.

Final Thoughts

Thermal control in semiconductor equipment is fundamentally an engineering integration problem.

The heater needs to work together with the mechanical structure, temperature sensors, control system, process requirements, and environmental conditions.

A successful design is not necessarily the heater with the highest power or highest rated temperature.

It is the heater that delivers the required thermal performance at the right location, with the right temperature distribution, while fitting reliably into the equipment.

For semiconductor equipment manufacturers, this approach can make thermal management more predictable and help improve process stability over long operating cycles.

Why Flexible Heaters Are Useful in Battery Thermal Management

jia yuying — Tue, 08 Sep 2026 07:04:17 +0000

Battery thermal management is usually associated with cooling. But for lithium-ion batteries operating in cold environments, heating can be just as important.

Low temperature can reduce charging performance, available power, and overall battery efficiency. In some applications, the battery needs to be preheated before charging or high-power operation.

This creates an interesting engineering problem:

How do you add enough heat to a battery system without taking up too much space or creating large temperature differences?

Flexible heaters are one practical answer.

The Heater Is Only One Part of the Thermal System

A flexible heater should not be treated as an isolated component.

A simplified battery heating system looks like:

Temperature Sensor → Controller / BMS → Heater → Battery

The heater generates heat, but the thermal performance depends on how that heat reaches the battery.

For example, a 100 W heater does not necessarily provide better heating than a 60 W heater. If the 100 W heater has poor contact with the battery surface, much of the heat may be lost to the surrounding structure.

This is why heater power, installation location, thermal interface, insulation, and temperature control need to be considered together.

Where Should a Flexible Heater Be Installed?

There is no universal installation position.

The right location depends on the battery architecture and the required thermal path.

1. Side of the battery module

A flexible heater can be attached to the side of a battery module when there is sufficient surface area and a suitable thermal path.

This approach can work well when the module structure allows direct heat transfer from the heater to the cells.

2. Bottom of the module

Bottom heating can provide a relatively large contact area and can be integrated with other layers of the battery structure.

However, engineers need to check the complete thermal path. Adding a heater underneath the module does not automatically guarantee uniform cell temperatures.

3. Battery enclosure

For stationary energy storage systems, the heater may be installed inside the battery enclosure rather than directly on individual modules.

This can be useful when the objective is to maintain the internal battery environment above a minimum temperature.

Outdoor energy storage introduces additional requirements, including humidity, condensation, thermal cycling, and mechanical durability.

Why Flexible Construction Matters

Battery packs are densely packed.

A typical design may include cells, cooling plates, busbars, sensors, structural components, and insulation within a relatively small volume.

A rigid heating element may not fit the available space.

A flexible heater can be manufactured to match the required shape and dimensions.

This is particularly useful when the heater needs to:

Fit into a narrow clearance
Follow a curved or irregular surface
Cover a specific area of a battery module
Avoid other components
Maintain a controlled heating pattern

The flexibility is therefore not just a mechanical feature. It can directly affect how the thermal system is packaged.

PI or Silicone?

Two common flexible heater constructions for battery-related applications are polyimide and silicone.

Polyimide heaters

PI heaters are useful when thickness and available space are major constraints.

A thin heater can be installed close to the target surface while adding very little thickness to the assembly.

This makes PI heaters interesting for compact battery modules and other applications with limited clearance.

Silicone heaters

Silicone heaters are useful when flexibility, surface conformity, and environmental durability are important.

They can be manufactured in different shapes and can follow curved surfaces more easily than many rigid heating solutions.

For outdoor energy storage applications, the overall heater construction also needs to be evaluated against moisture, temperature cycling, and the expected operating environment.

So the question is not simply:

“Which material is better?”

A better question is:

“Which heater construction fits the mechanical and thermal requirements of this battery system?”

Don't Design Around Wattage Alone

One of the easiest mistakes in battery heating design is selecting a heater based mainly on its wattage.

Consider two heaters:

Heater A: 60 W
Heater B: 100 W

It is tempting to assume that Heater B will heat the battery faster.

But the actual result depends on:

Heating area
Contact area
Heater position
Thermal conductivity of surrounding materials
Insulation
Ambient temperature
Battery mass
Heating time
Temperature control

A high-power heater concentrated in a small area may create local hot spots, while a lower-power heater distributed across a larger area may provide more uniform heating.

For battery systems, temperature distribution can be more important than maximum local temperature.

Temperature Uniformity Is a System-Level Problem

Suppose the heater is attached to the bottom of a battery module.

The cells closest to the heater may heat faster than cells farther away.

That means the battery may have an acceptable average temperature while still having a significant temperature difference between individual cells.

The solution may involve changing:

Heater geometry
Heating area
Heater position
Thermal interface material
Insulation
Heating power
Control strategy

This is why thermal simulation and prototype testing can be useful before finalizing the heater design.

How Temperature Control Fits In

A heater should normally be controlled according to the battery's actual temperature rather than simply running continuously.

A basic control strategy might be:

Measure battery temperature.
Compare it with the required operating range.
Activate the heater when temperature is too low.
Reduce or stop heating when the target temperature is reached.
Continue monitoring during charging and operation.

The actual control algorithm can be more complicated when the heater needs to work with the BMS, charging system, and cooling system.

The important point is that heater selection and control strategy should be considered together.

A Practical Engineering Checklist

Before specifying a flexible heater for a battery application, I would define these parameters first:

Mechanical

Available installation space
Heater dimensions
Surface shape
Mounting method
Clearance from other components

Electrical

Operating voltage
Required power
Resistance
Lead configuration
Electrical insulation requirements

Thermal

Starting temperature
Target temperature
Heating time
Heating area
Temperature uniformity
Thermal interface

Environmental

Ambient temperature
Humidity
Condensation
Vibration
Thermal cycling

This information gives the heater manufacturer a much better starting point than simply specifying “I need a battery heater.”

Final Thoughts

Flexible heaters are useful in battery thermal management because they allow the heating element to be designed around the battery rather than forcing the battery structure to accommodate a rigid heater.

But flexibility alone does not solve the thermal problem.

The important engineering questions are:

Where should the heat be introduced?

How will the heat reach the cells?

How uniform does the temperature need to be?

How will the heater be controlled?

Answering these questions first usually leads to a better heater design than starting with wattage or heater material alone.

For engineers working on EV batteries or energy storage systems, FLD develops customized silicone and polyimide heaters based on application-specific dimensions, voltage, power, resistance, and installation requirements.

You can find more information about its battery heating solutions here:

https://www.fldheaters.com/

How to Solve Temperature Uniformity Problems in Large Composite Presses

jia yuying — Mon, 07 Sep 2026 03:03:10 +0000

# How to Solve Temperature Uniformity Problems in Large Composite Presses

Temperature control is often treated as a simple heating problem: choose a heater, reach the target temperature, and maintain it.

In large composite processing equipment, that approach is usually not enough.

A press plate may reach the required average temperature while still having significant temperature differences between the center and edges. For processes involving epoxy, carbon fiber, fiberglass, or adhesive layers, these local differences can affect curing and bonding consistency.

The real engineering problem is often temperature uniformity, not simply maximum temperature.

This article looks at the common causes of uneven heating in large composite presses and several practical ways to improve the thermal design.

1. Why Large Press Plates Develop Hot and Cold Zones

A large heating surface does not automatically produce uniform temperature.

Several factors can create temperature differences:

Heater resistance distribution
Unequal heat loss at the edges
Press plate material and thickness
Contact quality between heater and plate
Heater watt density
Insulation around the equipment
Sensor location
Mechanical structure of the press

For example, the center of a press plate may retain heat better than the outer edges.

If the heater circuit delivers the same power density across the entire surface, the edges may still operate at a lower temperature because they lose more heat to the surrounding environment.

This is why simply increasing total heater power is not always the correct solution.

More power can increase the average temperature while leaving the underlying uniformity problem unresolved.

2. Start With the Heat Loss Distribution

Before changing the heater, it is useful to understand where heat is being lost.

For a large composite press, consider:

Press plate dimensions
Ambient temperature
Target processing temperature
Thermal conductivity of the plate
Insulation thickness
Edge heat loss
Contact conditions between heater and plate

The basic heat balance can be considered as:

Required heater power ≈ heat required for warm-up + continuous heat loss

During warm-up, a large amount of energy is required to raise the temperature of the press plate.

Once the system reaches steady state, the main requirement becomes compensating for continuous heat loss.

These are two different design conditions.

A heater designed only around warm-up speed may consume unnecessary power during steady operation. Conversely, a heater designed only for steady-state operation may heat too slowly during production startup.

3. Heater Layout Is More Important Than Total Wattage

One common mistake is to select a heater based primarily on total wattage.

For large-area applications, where the power is distributed can be more important than the total number of watts.

Consider a rectangular press plate.

If the heating circuit is concentrated in the center, the center may reach the target temperature quickly while the edges remain relatively cold.

A better approach is to design the heating circuit according to the actual thermal characteristics of the equipment.

Possible design strategies include:

Increasing heating density near high-loss areas
Reducing power density in areas that retain heat
Dividing the heater into multiple heating zones
Adjusting the circuit layout around mounting features
Leaving controlled areas for sensors and mechanical components

Flexible etched-foil heaters are particularly useful for this type of design because the resistance circuit can be developed around the required heating area.

4. Consider Zoning Instead of Using One Large Heating Circuit

For large press plates, a single heating zone may not provide enough control.

A multi-zone configuration can provide better thermal adjustment.

For example:

+-------------------------------+
|           Zone 1              |
|                               |
|  Zone 2               Zone 3  |
|                               |
|           Zone 4              |
+-------------------------------+

Each zone can be controlled independently or adjusted according to the measured temperature profile.

This makes it possible to compensate for differences caused by:

Edge heat loss
Uneven insulation
Different material thicknesses
Mechanical structures
Local heat sinks

The number of zones depends on the equipment size and the required temperature accuracy.

For some applications, two zones may be sufficient. Larger or more complex equipment may benefit from additional zones.

5. Sensor Placement Can Create a False Sense of Uniformity

Another problem is sensor location.

Suppose a temperature sensor is installed near the center of the press plate.

The controller may report that the system has reached the target temperature.

However, the edge of the plate could still be significantly cooler.

The controller cannot correct a temperature difference that it cannot measure.

For large heating surfaces, sensor placement should therefore be considered together with the heater layout.

Depending on the application, sensors may be positioned at:

Center areas
Edge areas
High heat-loss areas
Process-critical locations

Multiple sensors can provide a more realistic picture of the temperature distribution.

The important point is that temperature control accuracy depends not only on the sensor itself, but also on where the sensor is installed.

6. Heater-to-Plate Contact Matters

Even a well-designed heater can perform poorly if thermal contact is inconsistent.

Air gaps between the heater and the metal plate create additional thermal resistance.

This can result in:

Slower heat transfer
Local temperature differences
Longer heating times
Higher heater surface temperature
Reduced system efficiency

For flexible silicone heaters, installation should therefore provide consistent contact with the heated surface.

Depending on the equipment design, this can be achieved through adhesive bonding, mechanical fixation, or controlled pressure installation.

The mounting method should be evaluated as part of the thermal design rather than treated as a separate mechanical issue.

7. Why Flexible Silicone Heaters Work Well for Composite Presses

Composite processing equipment rarely has a completely standard geometry.

The heater may need to fit around:

Mounting holes
Bolts
Curved surfaces
Wiring channels
Temperature sensors
Mechanical structures

A rigid heating element can make this difficult.

A flexible silicone heater can be manufactured to match the required geometry and heating area.

This allows the heater design to be developed together with the press plate instead of forcing the equipment to accommodate a standard heater.

For large pressing equipment, this design flexibility can be particularly useful.

8. Don't Solve Every Problem by Increasing Power

When a press heats too slowly, the first reaction is often to increase wattage.

That can work—but it is not always the best engineering solution.

Higher power may cause:

Local overheating
Larger temperature overshoot
Higher electrical load
Greater thermal stress
Reduced heater life

Before increasing power, check:

Is the problem insufficient power, or is the power distributed incorrectly?

If the center is already reaching the target temperature while the edges remain cold, increasing total power may make the center hotter without adequately solving the edge problem.

In this situation, changing the heater layout or introducing independent heating zones may be more effective.

9. A Practical Design Workflow

A useful workflow for designing a heating system for a composite press is:

Step 1 — Define the process

Determine:

Target temperature
Heating time
Holding time
Press plate dimensions
Production cycle
Ambient conditions

Step 2 — Identify heat-loss areas

Pay particular attention to:

Plate edges
Mounting interfaces
Exposed metal surfaces
Areas with limited insulation

Step 3 — Develop the heater layout

Determine:

Heating area
Circuit pattern
Watt density
Heating zones
Wire exit position

Step 4 — Plan sensor locations

Sensors should represent the actual process temperature rather than simply measuring the easiest installation point.

Step 5 — Test the temperature map

Measure multiple locations across the press surface during:

Warm-up
Stabilization
Continuous operation

A temperature map can reveal problems that a single controller reading cannot.

Step 6 — Adjust the design

If the temperature distribution is not acceptable, consider changing:

Heating circuit density
Heating zones
Sensor locations
Insulation
Heater-to-plate contact

This iterative approach is usually more effective than simply increasing heater wattage.

10. Where This Approach Can Be Used

The same thermal design principles apply beyond ski and snowboard presses.

Examples include:

Carbon fiber molding
Composite panel pressing
Industrial laminating equipment
Adhesive bonding presses
Vacuum forming equipment
Composite tooling
Plastic forming systems

The materials and process temperatures may differ, but the engineering challenge remains similar:

How do you deliver the required amount of heat to the right locations and maintain a stable temperature distribution?

Final Thoughts

For large composite processing equipment, thermal management is not just about selecting a heater with sufficient power.

A reliable system requires the heater, press plate, insulation, sensors, control system, and installation method to work together.

If a press shows a large temperature difference between the center and edges, increasing heater wattage should not automatically be the first solution.

Start by analyzing the heat-loss distribution, heater layout, sensor locations, and thermal contact.

In many applications, a customized flexible silicone heater with an optimized resistance pattern and heating zones can provide a more practical solution.

For equipment manufacturers looking for customized heating elements for composite presses and other industrial thermal processing equipment, you can see more about custom silicone heating solutions here:

https://www.fldheaters.com/product/ski-press-silicone-heating-pad/

You can also learn more about FLD's approach to silicone heaters for composite processing and industrial press equipment:

https://www.fldheaters.com/blog/silicone-heater-ski-press-machine-manufacturing/

Designing Thick Film Heaters for EV Battery Thermal Management: A Practical Engineering Approach

jia yuying — Fri, 04 Sep 2026 07:22:45 +0000

When an EV battery system needs to operate in cold conditions, adding a heater is usually not the difficult part.

The difficult part is making the heater work efficiently, uniformly, and reliably within a limited mechanical space.

A heater may have the correct voltage and power rating on paper, but still perform poorly after installation because of thermal resistance, poor contact, uneven heat distribution, or an unsuitable control strategy.

This is where thick film heating technology becomes interesting.

Rather than treating a thick film heater as a simple replacement for a PTC heater, it is more useful to look at it as a heating element that can be designed around the thermal structure of the battery system.

The Real Problem: Heating the Battery Is Not Just About Heater Power

Consider a simplified EV battery heating system.

The battery starts at a low temperature and needs to reach a target operating range before charging or high-power operation.

A common engineering approach is to calculate the required heating power and then select a heater.

But the actual thermal response depends on much more than wattage:

Initial temperature
Target temperature
Battery or coolant mass
Heat loss to the environment
Thermal resistance
Contact area
Heating time
Heater location
Temperature sensor location
Control strategy

Two heaters with the same 1 kW rating can therefore produce very different system-level results.

The first design question should be:

Where should the heat be introduced into the thermal system?

1. Start With the Heat Transfer Path

For EV battery thermal management, there are several possible heating paths.

A heater may transfer heat directly to a metal thermal plate, heat a coolant circuit, or be integrated into a dedicated thermal structure.

The shorter and better controlled the heat transfer path is, the easier it is to achieve predictable thermal performance.

For example:

Heater → thermal plate → battery module

has a different thermal behavior from:

Heater → coolant → pump → cold plate → battery module

Neither architecture is automatically better.

The right choice depends on the battery pack design and the required heating response.

This is one reason thick film heaters can be useful: the heating element can be designed as part of a compact thermal structure rather than treated as a generic external component.

2. Don't Optimize Only for Maximum Temperature

A common mistake in heater design is focusing on the maximum heater temperature.

For battery applications, temperature distribution is often more important than maximum temperature.

Suppose a heating element produces sufficient total power but concentrates too much heat in one area.

The result may be:

Local hot spots
Uneven battery temperature
Increased thermal stress
More complicated control requirements
Reduced effective heating efficiency

The heating pattern should therefore be considered during the heater design stage.

With thick film technology, the resistance pattern can be designed according to the required heating area and power distribution.

This gives engineers more freedom to match the heater layout to the thermal structure.

3. Power Density Needs to Match the Thermal Structure

Higher power density is not automatically better.

If the heater produces high heat flux but the thermal interface cannot transfer that heat away effectively, the heater surface temperature can rise much faster than the target component temperature.

In other words:

Electrical power ≠ useful thermal power at the battery.

A simplified thermal path can be considered as:

Heater → interface → substrate → coolant / thermal plate → battery

Every interface introduces thermal resistance.

Therefore, when designing a thick film heater, power density should be evaluated together with:

Substrate material
Heating area
Contact area
Thermal interface material
Coolant flow rate, when applicable
Surface temperature
Heat dissipation capability

This system-level approach is much more useful than selecting a heater based only on its wattage.

4. Why Thick Film Heating Can Be Useful

Thick film heaters use a printed resistive heating element on a suitable substrate.

This construction provides several useful characteristics for EV thermal applications.

Compact construction

The heating circuit can be integrated into a relatively compact structure, which is useful when packaging space is limited.

High power density

The resistance pattern can be designed to concentrate heating power within a defined area.

Fast thermal response

A properly designed structure can reduce unnecessary thermal mass between the heating element and the target.

Custom geometry

The heater can be designed around the available mechanical structure rather than being limited to a standard rectangular heating pad.

Integration with metal structures

Metal substrates can provide a useful thermal path while also offering mechanical rigidity.

These characteristics make thick film technology worth evaluating for battery thermal management systems where packaging and thermal response are important design constraints.

More information about customized thick film heating structures is available on FLD's Thick Film Heater product page.

5. Thick Film vs. PTC: Think in Terms of System Requirements

It is tempting to ask:

Is a thick film heater better than a PTC heater?

That is usually the wrong engineering question.

PTC heaters have important advantages and are already widely used in automotive applications.

The better question is:

Which heater architecture fits the thermal system being designed?

A PTC solution can be attractive when its self-regulating characteristics and established system architecture fit the application.

Thick film heating becomes particularly interesting when the design requires:

Compact integration
Customized heating geometry
High heating power in a limited area
Direct integration with a thermal structure
Controlled heat distribution
Fast thermal response

The comparison should therefore be made at the system level, not simply by comparing heater specifications.

6. Temperature Sensors Should Be Designed With the Heater

Another issue that is often overlooked is sensor location.

The temperature measured by a sensor is not necessarily the actual temperature of the heating element.

For example:

Heater temperature ≠ thermal plate temperature ≠ coolant temperature ≠ battery temperature

If the sensor is positioned too far from the heating area, the control system may respond too slowly.

If it is placed too close to the heater, it may detect the heater temperature before the battery or coolant has reached the required temperature.

The sensor position should therefore be considered together with:

Heater layout
Heat transfer direction
Thermal mass
Expected temperature gradient
Control response

For a battery heating system, this can be just as important as selecting the heater's rated power.

7. Mechanical Design Matters More Than It Looks

EV battery systems experience vibration, thermal cycling, and changes in temperature over long operating periods.

The heater therefore needs to remain mechanically stable after repeated heating and cooling cycles.

Important design factors include:

Substrate selection
Mounting method
Thermal expansion
Surface flatness
Contact pressure
Insulation
Environmental protection
Connection design

A heater that performs well during a laboratory test may behave differently after integration into a vehicle system.

This is why heater development should include both thermal and mechanical considerations from the beginning.

8. A Better Way to Select a Thick Film Heater

Instead of starting with:

"I need a 500 W heater."

Start with the thermal requirement.

For example:

Step 1 — Define the target

What needs to be heated?

Battery module, thermal plate, coolant, or another component?

Step 2 — Define the temperature range

Determine:

Starting temperature
Target temperature
Maximum allowable temperature

Step 3 — Estimate heating power

Consider the thermal mass and required heating time, then account for heat loss.

Step 4 — Define the available installation space

Determine the maximum:

Length
Width
Thickness
Connection position

Step 5 — Design the heat transfer path

Identify how heat moves from the heater to the battery system.

Step 6 — Select the heater structure

Evaluate substrate, resistance pattern, heating area, insulation, and mounting method.

Step 7 — Design temperature control

Define sensor location, control method, and over-temperature protection.

This approach usually produces a more reliable design than selecting a standard heater first and trying to adapt it afterward.

When Should You Consider Thick Film Heating?

Thick film heating is particularly worth considering when several of these conditions exist at the same time:

Limited installation space

High heating power requirement

Fast thermal response

Customized heating geometry

Direct integration with a thermal structure

Controlled heat distribution

It is not necessarily the best solution for every EV battery application.

For applications where flexibility and conformable installation are more important, silicone heaters may be more suitable. For extremely thin and flexible heating requirements, polyimide heaters are another option.

The important point is to select the heater according to the thermal architecture, not simply according to the heater type.

Final Thoughts

Designing an EV battery heater is fundamentally a thermal-system problem.

The heater power is only one part of the equation.

A successful design needs to consider the complete path from electrical input to the final heat delivered to the battery or coolant.

Thick film heating can be a strong candidate when the system requires a compact, high-power-density heating element that can be integrated closely with the thermal structure.

For engineers working on a new battery thermal management project, the most useful starting point is not:

"Which heater should I buy?"

It is:

"Where does the heat need to go, how quickly does it need to get there, and what mechanical space is available?"

Once those questions are clear, the appropriate heater technology becomes much easier to determine.

If you are developing a customized EV battery heating solution, FLD works with OEM/ODM customers on heater dimensions, electrical specifications, heating patterns, substrate selection, and application-specific requirements. You can learn more about the company's custom thick film heater solutions.