DEV Community: jia yuying

Battery Heater Integration: 6 Engineering Issues to Consider Before Building a Prototype

jia yuying — Wed, 04 Nov 2026 06:31:50 +0000

When developing an EV battery pack or an energy storage system, adding a heating element may seem straightforward.

Select a heater, connect the power supply, install a temperature sensor, and control the heating process.

In practice, battery heater integration is more complicated.

The heater must fit the battery structure, transfer heat effectively, work with the temperature control system, and withstand the operating environment. A design that looks acceptable on paper may encounter problems during prototype testing.

Here are six engineering issues worth evaluating before building a battery heating prototype.

1. Heater Placement and Battery Geometry

The first challenge is often mechanical rather than electrical.

Battery modules contain cells, cooling channels, structural supports, wiring, and monitoring components. These elements restrict where a heater can be installed.

A standard rectangular heating pad may not provide sufficient coverage or fit the available installation space.

Before selecting a heater, review:

Battery module dimensions
Available heating surface
Installation clearance
Surface curvature
Mounting position
Cable routing
Connector location

For custom battery assemblies, heater dimensions and lead exits should be determined alongside the mechanical layout.

This can prevent unnecessary modifications after the first prototype is assembled.

2. Uneven Heating and Poor Thermal Contact

A heater can generate sufficient heat without transferring it evenly to the battery.

One common cause is poor thermal contact.

Air gaps, uneven surfaces, unsuitable adhesive layers, and inconsistent mounting pressure can all affect heat transfer.

Another issue is the heating element layout. If heat generation is concentrated in one area, the battery surface may develop temperature differences.

During prototype development, engineers should evaluate:

Contact between the heater and battery surface
Heating element distribution
Thermal interface materials
Mounting pressure
Insulation and heat loss
Temperature differences across the module

Increasing heater power is not always the right solution. Improving the thermal interface or changing the heater layout may produce better results.

3. Choosing the Appropriate Heater Construction

Different battery assemblies require different heater constructions.

Two commonly considered options are silicone rubber heaters and polyimide (PI) heaters.

Silicone Rubber Heaters

Silicone rubber heaters are useful when flexibility, durability, and larger heating areas are important.

They can be manufactured in customized shapes and dimensions to fit battery modules and other irregular surfaces.

Typical considerations include:

Flexible installation
Broad-area heating
Customized shapes
Environmental protection requirements
Integrated temperature sensors

They are commonly considered for battery modules, EV battery packs, and energy storage equipment.

Polyimide (PI) Heaters

PI heaters are useful when installation thickness and weight are major constraints.

Their thin construction makes them suitable for compact assemblies where available space is limited.

They may be considered for small battery components, compact electronics, and applications requiring lightweight flexible heating.

The decision should be based on the actual mechanical and thermal requirements, not simply on material preference.

For reference, FLD provides custom silicone rubber heaters and polyimide heater solutions.

4. Temperature Sensor Position and Control Logic

Temperature control is another area that deserves attention during early development.

A temperature sensor does not necessarily measure the temperature of the entire battery module. Its reading represents the temperature at its installation location.

If the sensor is too far from the heating area, or positioned where heat accumulates differently, the control system may not respond as expected.

Depending on the system architecture, engineers may consider:

NTC thermistors
RTD sensors such as PT100
Thermostats
External temperature controllers
BMS feedback

Sensor placement should be evaluated together with heater placement.

For EV and energy storage applications, the heating strategy should also coordinate with the battery thermal management system.

The objective is not simply to switch the heater on and off. It is to apply heat according to the actual thermal requirements of the battery.

5. Electrical Compatibility and Wiring

Electrical specifications need to match the available power system.

Important parameters include:

Operating voltage
Heater resistance
Rated power
Current
Power density
Wire length and gauge
Connector configuration

Wiring is sometimes overlooked during the initial design.

However, cable routing, insulation, strain relief, and connector space can become significant integration issues once the heater is installed inside a compact battery assembly.

These details should be included in the prototype drawing rather than left until final assembly.

6. Reliability Under Real Operating Conditions

Laboratory testing is only one part of heater validation.

A battery heating system may experience vibration, moisture, repeated thermal cycling, mechanical stress, and long operating periods.

The complete heater assembly should therefore be evaluated, including:

Heating element
Insulation
Adhesive system
Electrical leads
Connectors
Mounting structure
Sensor attachment

For outdoor energy storage systems, environmental exposure deserves particular attention.

A heater that performs well in an initial heating test may still require improvements to its wiring, mounting, or protective construction before it is suitable for long-term operation.

A Practical Workflow for Battery Heater Prototyping

To reduce redesign work, it helps to follow a structured development process.

Step 1: Define the thermal requirements

Identify the starting temperature, target temperature, heating area, and required heating time.

Step 2: Review the mechanical structure

Confirm available space, surface geometry, mounting method, and cable routing.

Step 3: Select the heater construction

Evaluate silicone rubber and PI options according to thickness, flexibility, heating coverage, and environmental requirements.

Step 4: Define the electrical configuration

Confirm voltage, power, resistance, wiring, connectors, and sensor requirements.

Step 5: Build and test the prototype

Evaluate temperature distribution, heating response, thermal contact, and control behavior.

Step 6: Validate reliability

Test the complete assembly under the environmental and mechanical conditions expected in the application.

What Information Should Be Prepared for Custom Heater Development?

When working with a heater manufacturer, a technical drawing and basic project specifications can make the development process much more efficient.

Useful information includes:

Category	Required Information
Dimensions	Length, width, thickness, shape
Thermal	Target temperature, heating area, heating time
Electrical	Voltage, power, resistance
Control	NTC, RTD, thermostat, sensor position
Mechanical	Mounting method, bending, cable exit
Environment	Moisture, vibration, thermal cycling

Not every project has all parameters finalized at the beginning. However, identifying the unknowns early makes it easier to evaluate design options.

Final Thoughts

Battery heater integration is not just an electrical design task.

Mechanical fit, thermal contact, temperature uniformity, sensor placement, wiring, and environmental reliability all influence the final result.

For engineers developing EV battery packs or energy storage systems, considering these factors before prototyping can reduce integration problems and avoid unnecessary redesign.

For additional application information, see FLD's EV heating solutions or battery energy storage heating solutions.

Polyimide Heaters in Electronic Devices: 8 Practical Applications and Design Considerations

jia yuying — Fri, 30 Oct 2026 03:48:47 +0000

As electronic devices become smaller and more integrated, thermal management is becoming an increasingly important part of product engineering.

Not every electronic device needs a large heating system. In many applications, only a specific component requires temperature control.

For example, a lithium battery may need additional heating in a cold environment, a security camera lens may require anti-fog heating, and an outdoor sensor may need protection from temperature fluctuations and condensation.

This is where polyimide heaters, also known as PI heaters or Kapton heaters, can provide a practical solution.

Their thin and flexible construction makes them suitable for compact electronic assemblies where installation space is limited and localized heating is required.

In this article, we explore eight common applications of polyimide heaters and the engineering factors to consider when integrating them into electronic devices.

1. Battery Heating Systems

Lithium battery performance can be affected by low ambient temperatures.

Depending on the battery chemistry and system design, cold conditions may reduce available power, increase internal resistance, slow down charging, or introduce charging restrictions.

A flexible PI heater can be integrated with a battery cell, module, or designated thermal interface to provide localized heating.

Typical applications include:

Lithium battery packs
Portable power stations
Battery-powered electronic devices
Energy storage systems
Electric vehicle battery modules
Backup power equipment

When designing a battery heater, engineers should consider battery dimensions, thermal transfer paths, ambient temperature, allowable temperature range, heating time, and available power supply.

The heater should be designed around the battery structure rather than selected only by nominal wattage.

2. Camera Lens and Optical Anti-Fog Heating

Outdoor cameras and optical systems can experience condensation when the lens or optical window temperature falls below the surrounding air's dew point.

Moisture on the optical surface may cause:

Blurred images
Reduced visibility
Poor image recognition
Frost formation in cold environments
Unstable monitoring performance

A polyimide lens heater can provide localized heat around the optical assembly to help maintain a suitable surface temperature.

Typical applications include:

CCTV cameras
Outdoor security cameras
PTZ cameras
Traffic monitoring cameras
AI vision cameras
Machine vision systems
Optical monitoring equipment

For compact camera assemblies, heater geometry is particularly important. The heating element may need to follow the shape of the lens housing or optical window.

Its position, mounting method, lead-wire routing, and heat distribution should all be considered during the mechanical design stage.

3. LCD and Display Heating

Electronic displays installed outdoors or in cold environments may require temperature compensation.

Potential applications include:

Outdoor LCD displays
Industrial control panels
Vehicle displays
Instrument panels
Touch-screen equipment
Outdoor information terminals

A display heating element can be integrated into the display assembly to provide localized temperature control when required.

One important consideration is thermal uniformity.

Uneven heating may create unwanted temperature differences across the display surface. Therefore, the heating pattern, installation position, and power distribution should be evaluated together.

4. Optical Equipment and Sensor Heating

Optical systems and electronic sensors can be sensitive to environmental temperature changes and condensation.

For outdoor or exposed equipment, moisture on an optical surface may interfere with imaging, detection, or measurement.

Localized PI heating can help maintain the required temperature conditions around sensitive components.

Typical applications include:

Optical sensors
Infrared equipment
Machine vision systems
Measurement instruments
Detection equipment
Imaging systems
Environmental sensors

In these applications, heater placement can be more important than simply increasing heating power.

The heating element should transfer heat to the target area without unnecessarily heating nearby electronic components.

5. Printers and Copiers

Printers and copiers contain several components and processes where controlled heating may be required.

Depending on the equipment structure, heating elements can be used around:

Rollers
Ink systems
Print heads
Toner-related components
Moisture-sensitive areas
Localized thermal processing sections

The heater design should match the actual process temperature, heating area, thermal mass, power requirements, and mechanical structure.

For compact printing equipment, available installation space is often a major design constraint.

A customized heating element can help fit the available mechanical assembly more effectively.

6. 3D Printers and Heated Build Platforms

Temperature control plays an important role in 3D printing.

A heated build platform is designed to maintain a controlled surface temperature during printing, helping establish suitable printing conditions for different materials.

Depending on the printer architecture, flexible heating elements may be considered for:

Heated beds
Build platforms
Printer enclosures
Localized thermal components
Certain resin-related temperature control applications

For a heated build platform, engineers should evaluate the heating area, target surface temperature, power supply, heat distribution, insulation, and mounting method.

The heater should be designed around the actual platform dimensions instead of being selected only according to its rated wattage.

7. Communication and 5G Equipment

Communication equipment is generally associated with cooling, but certain outdoor installations also require localized heating.

Environmental conditions may include:

Low ambient temperatures
High humidity
Condensation
Rapid temperature changes
Cold-weather startup conditions

A localized heater can help maintain suitable temperatures in selected areas of communication equipment.

Potential applications include:

Outdoor network equipment
5G communication systems
Communication enclosures
Electronic control units
Outdoor monitoring equipment

Engineers should consider enclosure heat loss, airflow, insulation, and the position of temperature-sensitive components before selecting a heater.

8. Electronic Enclosures and Control Boxes

Electronic devices installed in outdoor or semi-enclosed housings may experience significant temperature changes.

When the internal environment reaches conditions that favor condensation, moisture may accumulate on circuit boards, connectors, and electrical terminals.

A localized enclosure heater can help maintain a suitable internal temperature and reduce conditions that contribute to condensation.

Typical applications include:

Outdoor control cabinets
Security equipment
Communication enclosures
Monitoring systems
Electronic control boxes
Industrial electronic equipment

For larger enclosure surfaces or applications with different mechanical requirements, silicone rubber heaters may also be considered.

The most appropriate heating technology depends on the enclosure structure, heating area, environmental conditions, and required thermal performance.

Key Engineering Considerations When Selecting a PI Heater

Selecting a polyimide heater should start with the actual thermal problem rather than a predetermined heater size or wattage.

Engineers should evaluate the following factors:

Design Factor	Key Questions
Heating target	Which component needs to be heated?
Temperature	What operating temperature is required?
Heating area	How much surface needs localized heating?
Power supply	What voltage is available?
Thermal transfer	How does heat reach the target component?
Installation space	What dimensions and shapes are possible?
Mounting method	Is adhesive mounting or another fixing method required?
Temperature control	Is a thermistor, thermostat, or thermal protector needed?
Environment	Will the device operate in cold, humid, or outdoor conditions?

These factors help engineers avoid oversized heaters, inefficient placement, and unnecessary heating of surrounding components.

Why Heater Placement Matters

In compact electronic devices, increasing heater power is not always the best solution.

Consider a camera lens as an example.

If the heating element is installed too far from the optical surface, heat may be lost before reaching the area that needs temperature control.

The same principle applies to batteries, displays, and sensors.

During integration, engineers should evaluate:

Heat transfer paths
Contact area
Mounting surfaces
Thermal insulation
Surrounding materials
Ambient temperature
Heat dissipation

A properly positioned heater can provide more effective localized heating without unnecessarily increasing power consumption.

Custom Polyimide Heaters for OEM Electronics

Standard heating elements may not fit the mechanical structure of every electronic product.

OEM manufacturers often require customized heaters that fit around existing components or follow a specific installation area.

Common customization options include:

Heater length and width
Custom outline and geometry
Cutouts and mounting holes
Lead-wire position
Connector location
Operating voltage
Electrical resistance
Heating power
Temperature sensor position
Adhesive mounting options

For example, a camera manufacturer may need a ring-shaped heater designed around a lens assembly, while a battery manufacturer may require a long and narrow heating element that fits a specific battery module.

At FLD, customized polyimide heating elements are developed according to the mechanical and electrical requirements of different electronic applications.

The objective is to integrate the heater into the device structure while meeting its specific thermal requirements.

How to Choose the Right Heating Technology

There is no single heating solution suitable for every electronic device.

A battery heater, camera lens heater, display heater, sensor heater, and enclosure heater may have completely different design requirements.

Polyimide heaters are worth considering when an application requires a thin, lightweight, and flexible heating element for localized temperature control.

For larger surfaces or applications with different mechanical structures, silicone rubber heaters or other heating technologies may be more suitable.

The best approach is to select the heating technology according to the actual application rather than assuming that one heater type can solve every thermal problem.

Final Thoughts

Polyimide heaters are used in a growing range of electronic applications, from battery systems and security cameras to displays, optical sensors, printers, and communication equipment.

However, successful integration requires more than choosing a heater with the correct voltage and wattage.

Heating area, element geometry, thermal transfer, mounting position, power supply, and temperature control all influence the final result.

For OEM engineers developing electronic products, a customized PI heater can provide a compact and application-specific approach to localized heating.

Need a custom polyimide heater for your electronic device?

Visit FLD Heaters to explore flexible heating solutions or contact our team with your application requirements.

You can also learn more about our custom camera lens polyimide heater.

Originally inspired by FLD's technical article on Polyimide Heater Applications in Electronic Devices.

Designing EV Battery Module Heating: Thermal Paths, Power Density, and Temperature Control

jia yuying — Tue, 27 Oct 2026 03:09:50 +0000

When designing a heating system for an EV battery module, it is tempting to start with the electrical specification: voltage, wattage, and available installation area.

But these numbers do not tell the whole story.

A heater may produce the expected amount of heat and still fail to warm the battery module efficiently. The problem may be poor thermal contact, an unsuitable heating area, an unexpected heat-loss path, or a temperature sensor that measures the heater rather than the battery.

For compact battery assemblies, the real challenge is getting heat to the right place and controlling how it spreads.

This article outlines several practical considerations for battery module heating design.

1. Understand the Complete Thermal Path

Heat does not move directly from a heating element into a battery cell without resistance.

In a typical assembly, the path may include the heating element, an adhesive or interface layer, a metal support or cooling plate, and the battery cell itself.

Each layer affects heat transfer.

A small air gap, inconsistent contact pressure, or unsuitable interface material can increase thermal resistance. As a result, the heater may become hot while the battery warms more slowly than expected.

Before selecting a heating element, map the physical structure and identify the likely thermal path.

Questions worth asking include:

Is the heater in direct contact with the intended surface?
Does heat need to pass through a metal plate or another structural layer?
Could the cooling system absorb a significant amount of the supplied heat?
Are there areas where heat loss is likely to be higher?
Will the interface remain consistent after assembly?

These details can have a substantial effect on real-world performance.

2. Estimate the Required Heating Energy

A basic thermal calculation helps establish an initial power requirement.

The sensible heat required to raise the temperature of a mass can be approximated by:

Q = m × Cp × ΔT

Where:

Q is the thermal energy required
m is the mass being heated
Cp is the effective specific heat capacity
ΔT is the required temperature increase

If the target heating time is known, a first estimate of average thermal power is:

P = Q / t

This is only an initial estimate. It does not account for heat loss, temperature-dependent material properties, uneven heat transfer, or energy absorbed by surrounding components.

The calculation is still useful because it provides a starting point for testing rather than relying on an arbitrary wattage.

One important distinction: the calculated thermal power delivered to the battery is not necessarily equal to the electrical power consumed by the heater. The difference depends on the efficiency of the complete thermal path.

3. Total Wattage Is Not the Same as Heating Performance

Consider two heaters with the same rated power.

One distributes heat across a relatively large area. The other concentrates the same power into a smaller zone.

Their total electrical power may be identical, but their local thermal behavior can be very different.

Power density is commonly expressed as:

Power density = Electrical power / Active heating area

A higher power density can support faster local heating, but it can also increase temperature gradients if heat cannot spread effectively through the surrounding structure.

A lower power density may provide a more gradual temperature rise, but the system may require more time to reach its target.

The right balance depends on the cell arrangement, thermal interface, available heating time, and allowable temperature variation.

The goal is not simply to maximize power density. It is to provide enough heat in the right location without creating unacceptable local temperature differences.

4. Decide Where Heating Is Actually Needed

Full-area heating is not always the best solution.

Some battery modules have relatively uniform thermal conditions. Others have cold spots caused by structural geometry, uneven insulation, or different heat-transfer paths.

Localized heating may be worth evaluating when only certain areas require additional thermal input or when installation space is limited.

However, localized heating also introduces a design trade-off. Heat must spread from the heated region to the rest of the intended area without creating excessive gradients.

The decision should be based on the thermal behavior of the assembled module, not just the shape of the available surface.

A useful development process is to compare several heating layouts and measure the temperature distribution under the same test conditions.

This helps determine whether a larger heating area, a different heating pattern, or a change to the interface would improve the result.

5. Treat Temperature Uniformity as a Design Requirement

A single temperature reading can hide important differences across a battery module.

For example, a sensor might report that the module has reached a target temperature while some areas remain substantially colder.

This matters because the average temperature alone does not describe the thermal condition of every cell.

During prototype testing, multiple measurement points can help identify:

The fastest-heating region
The slowest-heating region
Local temperature peaks
Persistent cold spots
Differences between heater temperature and cell temperature

The resulting temperature map provides a basis for refining heater geometry, power distribution, insulation, and sensor placement.

The relevant acceptance criteria should be defined for the specific battery design and operating conditions. There is no single temperature-uniformity target that applies to every module.

6. Place Temperature Sensors According to What Needs to Be Controlled

Sensor placement is closely connected to the thermal path.

A sensor located near the heating element may respond quickly because it measures a region that receives heat directly. The battery cell may respond more slowly.

If the control system relies only on this local reading, it may reduce or stop heating before the intended battery region has reached the required condition.

The appropriate sensor location depends on the control objective.

It may be necessary to monitor a representative cell surface, a known cold spot, a critical structural location, or more than one point.

Sensor position should therefore be decided during thermal design rather than added as an afterthought.

The control strategy also needs to account for sensor accuracy, response time, heater limits, and the battery management system's operating requirements.

7. Consider Heating and Cooling as One System

Battery heating and cooling share the same physical structure, but their thermal objectives are different.

During cooling, a plate or other thermal component removes heat from the battery. During preheating, that same component may absorb some of the energy supplied by the heater.

This can increase the energy needed to warm the battery and change the expected heating time.

Testing only the heater on an isolated surface may therefore produce results that do not represent the final assembly.

Where possible, prototype testing should reproduce the relevant mounting structure, thermal interface, insulation, and cooling-system configuration.

The closer the test setup is to the intended application, the more useful the results will be for design decisions.

8. Validate the Complete Assembly

Calculations help narrow the design range, but testing determines whether the proposed system works as intended.

A practical test plan should record:

Initial battery and ambient temperatures
Applied voltage and electrical power
Heater temperature
Temperatures at representative battery locations
Heating time
Temperature variation across the module
Changes under relevant cooling or insulation conditions

The data should be reviewed against the original requirements.

If the heater reaches its target temperature quickly but the battery remains cold, increasing power may not be the most effective next step. The thermal interface or heat-transfer path may be the limiting factor.

If one area heats much faster than the rest, the heating layout or power distribution may need to change.

This is where temperature measurements become more valuable than assumptions.

A Practical Design Sequence

For a new battery module heating project, the following sequence provides a useful starting point:

Define the initial and target battery temperatures.
Establish the required heating time.
Estimate the thermal energy and initial power range.
Map the thermal path and identify likely heat losses.
Select candidate heating areas and layouts.
Review power density and interface conditions.
Determine sensor locations and control requirements.
Test a representative assembly.
Use temperature data to refine the design.

The key is to evaluate the heating element as part of a complete thermal system.

Final Thoughts

EV battery module heating is not simply a matter of selecting a heater with sufficient wattage.

The result depends on where heat enters the structure, how it travels through the interface, how evenly it reaches the intended areas, and how the control system measures the battery's thermal condition.

For compact modules, these considerations are especially important because installation space is limited and the thermal path may be constrained by the surrounding components.

A useful design starts with the battery architecture and its thermal requirements. Heater selection comes after those requirements are understood.

For a more detailed discussion of EV battery module heating design, see this related engineering article:

EV Battery Module Heating Design: When Thin, Localized Heating Makes Sense

The central question is not just how much heat the system can generate, but how effectively that heat reaches the battery.

BatteryEngineering #ThermalManagement #ElectricVehicles

Thick Film Heaters for EV Thermal Management: Engineering Considerations Beyond Power Density

jia yuying — Thu, 22 Oct 2026 05:38:09 +0000

Electric vehicle thermal management is often discussed in terms of cooling. Battery packs, power electronics, and electric motors all generate heat that must be removed under certain operating conditions.

But in cold environments, the opposite problem becomes equally important: how can heat be delivered efficiently, uniformly, and within a limited installation space?

Thick film heaters are one option for addressing this challenge. Their potential value comes not simply from generating heat, but from integrating a resistive heating circuit with a substrate designed for a particular thermal application.

This article looks at how thick film heating works, where it may fit into EV thermal systems, and what engineers should evaluate before selecting a heating element.

Why EV Thermal Systems Need Active Heating

Lithium-ion batteries are sensitive to operating temperature. At low temperatures, charging capability and available power may decrease. Charging a cold battery under unsuitable conditions can also increase the risk of lithium plating, depending on cell chemistry, state of charge, and charging conditions.

Preheating can help bring a battery closer to its required operating range before charging or high-power operation.

However, heating an EV battery is not as simple as increasing heater wattage.

Engineers must consider:

The battery's initial temperature and target temperature

The thermal mass of the battery pack

The required warm-up time

Temperature differences between cells and modules

Heat losses to the enclosure and surrounding environment

Available electrical power and control requirements

A heater that produces sufficient total energy may still create uneven temperature distribution if heat transfer and installation are poorly designed.

How Thick Film Heating Works

A thick film heater typically uses a resistive heating pattern formed on a suitable substrate. When electrical current passes through the resistive circuit, electrical energy is converted into heat.

Depending on the design, the substrate may be integrated with a metal structure or another thermally functional component. This can provide a direct heat-transfer path to the target component or a heat-transfer medium.

The final performance depends on more than the resistive material itself. Substrate properties, circuit layout, insulation, mounting pressure, interface materials, and temperature sensing all influence the thermal result.

This is why thick film heaters should be evaluated as part of a thermal assembly rather than as isolated heating elements.

Potential Applications in Electric Vehicles

Battery preheating

A thick film heating element may be incorporated into a battery thermal-management assembly to help warm the pack before charging or operation.

The important design question is how uniformly the heat reaches the intended areas. Engineers should assess the location of the heating element, the contact between surfaces, and temperature differences across the battery module.

High-voltage coolant heating

In liquid-based thermal-management systems, a heater can transfer energy to coolant, which then distributes heat through a circuit.

In this configuration, performance depends on the interaction between electrical heating, coolant flow, heat-transfer surfaces, and temperature control. Flow rate and local hot spots must be considered alongside nominal power.

Cabin and auxiliary heating

Electric vehicles cannot rely on engine waste heat in the same way as conventional combustion vehicles. Dedicated electric heating may therefore be required for cabin comfort or other auxiliary thermal functions.

Thick film technology can be considered where compact construction and integration with a heat-transfer structure are useful. Whether it is suitable depends on the required output, operating environment, and system architecture.

Thick Film vs. Silicone and Polyimide Heaters

Different heater technologies solve different installation problems. Choosing one based on a single specification can lead to a poor design decision.

Technology

Potential advantages

Typical design consideration

Thick film heater

Can integrate a resistive circuit with a functional substrate or heat-transfer structure

Substrate design, heat-transfer path, insulation, and assembly requirements

Silicone rubber heater

Flexible, conformable, and suitable for heating curved or irregular surfaces

Contact quality, mechanical attachment, and surface temperature distribution

Polyimide (PI/Kapton) heater

Thin, lightweight, and useful where installation space is limited

Mechanical protection, electrical insulation, and heat-transfer interface

PTC heater

Self-regulating behavior may be useful in suitable designs

Temperature characteristics, system-level control, power requirements, and packaging

These are general characteristics, not guarantees for every product. Actual performance depends on the specific heater construction and operating conditions.

For example, a flexible silicone heater may be a better fit when it needs to conform to a battery enclosure. A PI heater may be preferable when thickness and weight are critical. A thick film design may be worth evaluating when the heating circuit can be integrated with a substrate or thermal structure.

The goal is to select the technology that best fits the heat-transfer path and system constraints.

Five Engineering Factors to Check Before Selecting a Heater
Thermal load

Estimate the energy required to raise the target component from its initial temperature to the desired operating temperature.

A simplified starting point is:

Q = m × c × ΔT

Where:

Q is the required thermal energy

m is the mass of the component

c is its specific heat capacity

ΔT is the required temperature change

This calculation provides an initial estimate, not the complete heater rating. Real systems also lose heat to the environment and surrounding structures.

Power and voltage

The available voltage, target power, current limits, and electrical architecture must be compatible with the heating circuit.

High-voltage operation also requires appropriate insulation, dielectric testing, spacing, and protection according to the system's applicable requirements.

Heat-transfer interface

The heater may generate the expected amount of heat while the target component warms too slowly because the interface introduces excessive thermal resistance.

Engineers should evaluate substrate contact, mounting pressure, interface materials, coolant flow where applicable, and the thermal properties of adjacent components.

Temperature sensing and control

A temperature sensor should measure a location relevant to the control objective. Measuring only the heater's own surface may not accurately represent the temperature of the battery, coolant, or other target.

Sensor placement, response time, control logic, and independent overtemperature protection should be considered during system design.

Environmental and lifecycle requirements

Automotive applications may involve vibration, humidity, thermal cycling, chemical exposure, and repeated power cycles.

The heater and its assembly should be evaluated against the actual operating environment, including electrical insulation, sealing, mechanical durability, and reliability requirements.

Why Heater Integration Matters More Than Nominal Wattage

Consider two heating assemblies with the same rated power. One transfers heat efficiently to the target surface, while the other has poor contact and significant heat loss.

The two assemblies can produce very different warm-up times and temperature distributions despite having identical electrical ratings.

This is why thermal design should consider the complete energy path:

Electrical input → resistive heating element → substrate → interface → target component

For liquid heating, the path also includes heat transfer from the assembly into the coolant and transport through the fluid circuit.

A successful design must account for each stage rather than treating rated power as the only performance indicator.

When Should Engineers Consider a Custom Thick Film Heater?

A custom design may be worth evaluating when standard components cannot meet the required geometry, power distribution, mounting conditions, or thermal performance.

Before requesting a design, engineers should define:

Available installation dimensions

Operating voltage and target power

Target temperature and warm-up requirements

Substrate and mounting preferences

Temperature sensor and control requirements

Environmental and electrical safety requirements

Expected operating cycles and service life

Providing these details early helps narrow the design options and makes prototype evaluation more meaningful.

Conclusion

Thick film heaters can be a useful option for EV thermal management when the heating circuit, substrate, and heat-transfer structure can be designed to work together.

They are not a universal replacement for silicone heaters, polyimide heaters, or PTC solutions. Their suitability depends on the application, thermal interface, electrical requirements, and packaging constraints.

For engineers, the key question is not simply how much power a heater can generate. It is how effectively that energy reaches the intended component under real operating conditions.

For more information, see FLD's thick film heater product page or read the related guide on thick film heaters for EV thermal management.

Why EV Battery Heating Can Fail Even When Average Temperature Looks Normal

jia yuying — Mon, 19 Oct 2026 07:00:37 +0000

A battery module can reach its target average temperature and still have a heating problem.

This is easy to miss if the system is evaluated using only one temperature reading.

For EV battery heating, the real challenge is not simply generating enough heat. It is getting that heat to the right places, within the required time, without creating excessive temperature differences.

Here are several engineering factors worth checking when a battery heating system does not perform as expected.

1. Average Temperature Hides Local Hot and Cold Spots

Imagine a battery module with an average temperature of 15°C.

That number looks straightforward. But individual areas might be at 8°C, 14°C, 18°C or 20°C.

The average does not reveal how evenly the module has heated.

This matters during cold-weather preheating, when some parts of the battery may warm faster than others.

Troubleshooting tip: Record temperatures at multiple representative locations instead of relying on a single sensor or the module average. Compare the minimum, maximum and temperature spread throughout the heating cycle.

The acceptable temperature difference depends on the battery design, chemistry and operating requirements, so it should be defined by the application rather than assumed.

2. Increasing Heater Power May Not Fix the Root Cause

When heating takes too long, increasing power can seem like the simplest solution.

However, higher power does not automatically improve temperature uniformity.

If the heat source is concentrated in one area, the nearby surface may become warm while heat takes longer to reach more distant cells.

Before changing the power rating, examine:

Heater coverage and location
Thermal contact between the heater and module
Heat conduction through structural components
Insulation and heat loss
Available installation space

A better heating layout may improve temperature distribution without simply increasing power consumption.

3. Heater Placement and Thermal Contact Matter

Flexible heaters are often used when battery assemblies require thin, lightweight or customized heating elements.

Silicone rubber heaters can be suitable for flexible surface heating and custom geometries. Polyimide heaters can be useful where installation space and low thickness are important.

Neither material guarantees uniform heating on its own.

The outcome depends on the complete thermal path: heater, interface, module structure and cells.

For an overview of application-specific options, see EV Battery Heating Solutions.

When evaluating a design, check whether the heater makes consistent contact with the intended surface. Air gaps, uneven pressure and variations in interface materials can change local heat transfer.

4. Sensor Placement Can Misrepresent the Module

A temperature sensor measures the temperature at its own location, not across the entire battery.

If the sensor is positioned near a warm area, it may reach the control threshold before colder regions have caught up.

That can make the system appear to finish preheating earlier than expected.

During testing, consider:

Whether the sensor is too close to the heater
Whether likely cold spots are being monitored
Whether additional measurement points are needed
Whether surface temperature adequately represents the parameter being controlled

Sensor placement should be evaluated alongside heater placement and the control strategy.

5. Test the Temperature Profile, Not Just the Final Value

A useful heating test should capture how temperature changes over time.

At minimum, record:

Initial temperature at each measurement point
Heating rate at representative locations
Maximum and minimum temperatures
Temperature difference during heating
Time required to reach the target range
Temperature behavior after heating power is reduced or switched off

Thermal imaging can help identify surface hot spots and cold regions. However, it does not directly reveal internal cell temperatures, so its findings should be interpreted alongside suitable contact sensors or other validated measurements.

Testing should reproduce relevant ambient conditions, mounting pressure, insulation and operating constraints as closely as practical.

A Practical Engineering Checklist

When a battery heating system is too slow or heats unevenly, investigate in this order:

Measurement: Are the sensors capturing representative locations?
Thermal path: Where is heat being lost or delayed?
Contact: Is the heater consistently coupled to the intended surface?
Coverage: Does the heating area match the module geometry?
Control: Does the heating logic respond appropriately to temperature differences?
Validation: Has the design been tested under realistic conditions?

This approach helps distinguish a heater-power problem from a layout, interface, sensing or control problem.

Final Thought

A normal average temperature does not necessarily mean a battery module is heating uniformly.

For EV battery thermal management, heater power, placement, thermal contact and sensor location need to be considered together.

The most useful question is not just, “Has the battery reached its target temperature?”

It is also, “What is the temperature distribution across the module, and how does it change during heating?”

That question leads to better troubleshooting and a more complete evaluation of the heating system.

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.

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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