A fast-speed heater with internal and external heating for lithium-ion batteries at low temperatures

This paper proposes an automotive on-board heater for lithium-ion batteries at low temperatures without the requirement of external power supplies. The proposed heater only needs one MOSFET for one cell, resulting in a smaller size and lower cost, which can be easily applied to electric vehicles (EVs). One high-frequency PWM signal is employed to drive all MOSFETs, and batteries can be heated internally by the ohmic losses and warmed externally by the switching losses and conduction losses of MOSFETs, leading to a high heating speed and efficiency. In addition, the proposed system with a higher switching frequency and smaller duty cycle can also realize the passive balancing for battery cells. Experimental results show that the proposed heater, by generating a periodic ramped discharged current with the amplitude of 3.7 C and the switching frequency of 150 kHz, can heat Lithium-Ion batteries from -20 °C to 0 °C within 1.9 min, consuming about 5 % of cell energy.