Flex-PCB Battery Heater for -40°C Arctic Deployment

Challenge: Keep Li-Ion batteries above -20°C inside an environmental monitoring enclosure rated for -40°C. The heater has to wrap around an irregular battery compartment. Solution: Flex PCB with resistive heating traces on one layer and a copper heat spreader on the other. Serpentine pattern sized to deliver uniform W/cm² across the battery surface. Thermal simulation guided the trace density to eliminate hot spots. The heater activates when battery temperature drops below -10°C and shuts off at 0°C to conserve energy. Results: Temperature variation across the battery surface stays within ±3°C, compared to ±15°C with the wire heater it replaced. No mechanical fasteners needed; the flex conforms directly to the compartment.