Heating Character of a LiMn₂O₄ Battery Pack at Low Temperature Based on PTC and Metallic Resistance Material

After long cold winter nights, the direct use of a deeply frozen Lithium-ion pack in an electric vehicle(EV) would cause detriments to its battery performance and life. In this research, a battery pack of a dual-source trolley bus, consisting of 35Ah large format prismatic LiMn₂O₄ cells, is taken as the object. Series of experiments are designed to simulate a winter night standing condition and subsequent pre-heating procedure. Two of the current applied pre-heating methods, PTC (Positive Temperature Coefficient) material and metallic resistance (MR) material heating method are selected, tested and compared to indicate the battery temperature variation characteristics during the heating process. Furthermore, experiments under the condition of enforced air ventilation by a set of electric fans are conducted, in order to research the influence of air circulation during heating process.