EV Battery Thermal Management with Flexible Heaters: What You Need to Know

Electric vehicles (EVs) depend on lithium-ion batteries that are highly sensitive to temperature changes. In cold environments, battery capacity and charging efficiency drop significantly, reducing range and performance. To address this, EV battery thermal management systems regulate battery temperature to maintain optimal operating conditions. Flexible heaters are a key component of these systems, providing fast and even warming directly to the battery pack to maintain safe, reliable operation and extend battery lifespan.

How Does Heat Affect EV Batteries?

Temperature plays a vital role in EV battery efficiency and longevity. Lithium-ion batteries ideally operate between 20°C and 40°C. When temperatures fall below this range, electrochemical reactions slow down, the electrolyte thickens, reducing ion mobility and limiting discharge capacity and driving range. Charging below 0°C risks lithium plating on the anode, a permanent issue that damages capacity and increases the likelihood of internal short circuits. Cold conditions also increase internal resistance, which reduces power output while generating unwanted heat.

At the other extreme, overheating above 45°C accelerates battery degradation and can trigger thermal runaway. Therefore, incorporating flexible heaters as part of an effective thermal management system is essential to maintaining optimal temperatures, safeguarding performance, and extending battery lifespan.

How Do Flexible Heaters Work?

Flexible heaters convert electrical energy into heat via a thin resistive element embedded in a flexible substrate. When applied to an EV battery pack, they distribute heat evenly to maintain the cells within the ideal temperature window (approximately 20–40°C).

These heaters are typically controlled by the vehicle’s Battery Management System (BMS) or dedicated thermostats, enabling:

• Preheating: Warm the battery before charging to improve efficiency and shorten charge times.

• Temperature maintenance: Stabilize battery temperature during cold weather driving.

• Battery protection: Prevent irreversible cold-induced damage like lithium plating.

Flexible Heater Construction and Customization Options

A typical EV battery flexible heater comprises:

• Insulation Layer: Made of polyimide (PI) or silicone rubber.

￮ Polyimide can withstand -200°C to +300°C, offers excellent electrical insulation, chemical resistance, and is ultra-thin (0.1–0.3 mm), ideal for space-constrained battery packs.

￮ Silicone rubber is thicker but provides superior flexibility, mechanical strength, and resistance to moisture, chemicals, and vibration—perfect for harsh environments.

• Heating Element: Usually composed of metal alloys such as brass, stainless steel, or iron-chromium-aluminum (FeCrAl), selected for stable, precise heat generation tailored to battery thermal requirements. Optimizing element material selection ensures not only thermal efficiency but also long-term stability under EV operating conditions.

Choosing the Right Flexible Heater for Your EV Battery

• Operating temperature range: Must suit your local climate and battery specs.

• Heating power density: Higher power densities enable faster warm-up but consume more energy.

• Voltage compatibility: Ensure alignment with the EV system voltage for safe operation.

• Material selection: Use PI heaters for thin, precise, space-saving applications, and silicone heaters for rugged, durable needs.

• Installation constraints: Heater size, shape, and mounting options should fit battery pack design.

• Optional features: Adhesive backing, wire protection sleeves, solder joint sealing, integrated sensors, and thermostats.

Due to differing customer needs, ordering options often include glass fiber sleeves and various adhesive backing choices.

Adhesive Backing

To simplify heater installation on battery packs, many users opt for flexible heaters with adhesive backing. JLCPCB Flexible Heater offers several 3M adhesive options, including 3M 8448A, 3M 468MP, 3M 55236, Crown 513. These differ in temperature resistance and thickness. Customers usually select adhesive backing on the non-wiring side to avoid interference with solder joints.

Wire Protection: Glass Fiber Sleeves

The wires connecting heaters to battery systems require effective protection to ensure safety and longevity. Glass fiber sleeves, also known as ceramic or high-temperature fiber sleeves, are commonly used for this purpose. They offer excellent resistance to high temperatures and provide superior thermal insulation, helping to shield the wires from heat generated during battery operation.

Additionally, these sleeves are flame retardant and electrically insulating, reducing the risk of short circuits. Their strong chemical resistance protects against potential exposure to battery electrolyte leaks, including acids and alkalis. Mechanically, glass fiber sleeves are highly durable, offering abrasion resistance and the ability to withstand constant vibration and friction commonly experienced in EV environments. Moreover, they provide a cost-effective solution to wire protection, helping to prevent damage and extend the overall durability of the battery’s wiring system.

Solder Joint Protection: Potting vs. Silicone Pad Sealing (Compression Packaging)

When wiring is needed, JLCPCB Flexible Heater provides Dot Adhesive and Silicone Pad Sealing that fit different mechanical and environmental demands.

• Dot Adhesive: Enhances solder joint strength and insulation but can be fragile.

• Silicone Pad Sealing: It is for flexible heaters that require wire connections or long-term use in humid or corrosive environments, improving waterproofing, corrosion resistance, and ensures durability and reliability.

Installation Options: Where and How to Place Flexible Heaters

In new energy vehicle lithium battery packs, flexible heaters are typically installed in three ways: on the module side, on both the side and bottom, and within the gaps between batteries. The module side installation can be further divided into single-sided and double-sided mounting.

With the same total power, the heating time for all three installation methods is basically similar and decreases as the heating power increases. However, installing heaters on both the battery’s side and bottom can effectively reduce the average temperature of the heating film, thereby enhancing safety during use.

Conclusion

Maintaining EV lithium battery temperature within the optimal range is crucial for maximizing capacity, safety, and lifespan. Flexible heaters, whether polyimide or silicone, offer efficient, customizable solutions for rapid preheating and reliable thermal regulation. Their lightweight, thin profiles and seamless integration with battery management systems make them indispensable components in EV battery thermal management.