Thermal Design Optimization of PTC Heating Films for EV Battery Preheating and Insulation
As electric vehicles (EVs) gain widespread adoption, the need for efficient and reliable battery thermal management is becoming more critical than ever. Among the available technologies, PTC heaters stand out as the preferred solution for EV battery preheating and insulation, offering safe, stable, and energy-efficient performance in all climate conditions.
At XingHongChang Electric Co., Ltd., we specialize in developing advanced PTC heating films tailored for EV battery applications. In this article, we share our insights into the optimal temperature design of PTC heating films based on industry standards, battery chemistry, and field-proven application cases — helping OEMs and integrators achieve better performance, safety, and efficiency.
Learn more about our technology at XHC Heater, your trusted source for PTC heaters, flexible PTC heating films, and reliable PTC heaters manufacturers in China.
🔧 Typical Working Temperature Ranges of PTC Heating Films in EV Battery Systems
To ensure both rapid preheating and consistent thermal insulation, PTC heating films must operate within a carefully defined temperature window.
1. Preheating Phase (Cold Start / Pre-Charging Heating)
Target surface temperature: 40°C – 60°C
Function: Raise the battery cell temperature from sub-zero conditions (e.g., -30°C ~ 0°C) to 20°C – 35°C — the ideal operational temperature for lithium-ion batteries.
Example: At -10°C ambient, the heating film must elevate cell temperature to >20°C within 30 minutes. This requires maintaining the surface temperature at 40°C – 55°C for effective heat transfer.
2. Insulation Phase (Driving or Parking Mode)
Target surface temperature: 35°C – 50°C
Function: Maintain the battery’s temperature after it reaches the desired range (20°C – 35°C), compensating for thermal loss and preventing performance degradation.
Example: In cold environments during vehicle operation, PTC heaters help retain optimal battery temperature, reducing the risk of the battery dropping below 15°C, which can cause noticeable capacity and power loss.
⚙️ Why Temperature Control Precision is Critical for Battery Safety and Efficiency
The required temperature range is not arbitrary. It is a result of rigorous considerations related to battery chemistry, safety, energy efficiency, and thermal uniformity.
1. Lithium-Ion Battery Chemistry
Low temperatures (<10°C) reduce ion mobility, causing capacity loss and posing risks such as lithium plating.
Optimal range (20°C – 35°C) ensures peak efficiency, cycle life, and charging performance.
Therefore, PTC heating films must operate at surface temperatures 10°C – 25°C higher than battery target temperatures to ensure effective heat delivery.
2. Safety Margins
Overheating can cause thermal runaway due to:
Electrolyte decomposition (>60°C)
Cathode degradation (>80°C)
To prevent safety hazards, most EV manufacturers — including BYD — require surface temperatures ≤ 60°C, with tighter limits around 55°C.
XHC’s PTC heating films are designed to self-regulate and maintain precise temperature control under dynamic environmental conditions.
3. Energy Efficiency & User Experience
Excessive heat (>60°C) leads to high thermal losses and reduced vehicle range.
Insufficient heat (<35°C) causes slow warm-up times, especially in extreme cold.
An optimized range of 40–60°C for preheating and 35–50°C for insulation balances heating speed with energy consumption.
4. Temperature Uniformity
EV battery packs contain hundreds of cells — uneven heating leads to:
Accelerated aging of hotspots
Cell imbalance and reduced pack life
XHC’s heating films maintain ±3°C temperature uniformity, achieved through advanced material formulation (silver paste + carbon ink) and fine-tuned circuit layout.
✅ Conclusion: Precise Thermal Design = Better Battery Performance
To support EV battery efficiency, longevity, and safety, PTC heating films must operate within the optimal surface temperature ranges:
40°C – 60°C for preheating
35°C – 50°C for insulation
These design parameters align with the chemical behavior of lithium-ion batteries, their thermal limits, and the operational expectations of top-tier EV brands like BYD. At XHC Heater, we deliver reliable, customized heating film solutions engineered for this exact purpose.
Visit https://xhc-heater.com to learn how our PTC heaters, flexible heating films, and full-stack engineering capabilities can help your EV project succeed. As a reliable PTC heaters manufacturer, we are committed to safety, performance, and innovation.
