To improve the low-temperature charge-discharge performance of lithium-ion battery, low- temperature experiments of the charge-discharge characteristics of 35 Ah high-power lithium-ion batteries have been conducted, and the wide-line metal film method for heating batteries is presented. At ?40 °C, heating and charge-discharge experiments have been performed on the battery pack. The results indicate the charge-discharge performance is substantially worse in cold climates, and can be significantly improved by heating the battery pack with a wide-line metal film. Pulse charge-discharge experiments show that at ?40 °C ambient temperature, the heated battery pack can charge or discharge at high current and offer almost 80% power.