Li batteries used in electric vehicles have a high discharge voltage and an excellent energy density. However, in a low-temperature environment, the output of the lithium battery sharply decreases, which reduces the total cruising distance. We developed film type battery heater for enhancing Li battery performance at a cold state. This battery heater can increase the temperature of Li-ion battery soaked at cold state below from –20℃ to 0℃ within several minutes. To test performance of battery heater developed in KETI, various stacking structures (Al/battery heater/Al) depending on thickness of Al plate were prepared and were soaked at –20℃ for a day. While DC 4V was applied to the battery heater, the surface temperature of Al plate increase dramatically to above 0℃ within several mins. As decreasing in thickness of Al plate, the heat-up speed get faster. It ensured almost stable heating behavior without degradation of performance even with increasing in the number of on / off cycling.