After a generation of technological changes in lead-acid batteries, nickel-cadmium batteries and nickel-hydrogen batteries, most of today's mainstream
electricvehicles use battery packs with lithium batteries as the core. The main reason lies in the multiple advantages of lithium batteries, which have better
energy-weight ratio,better charging and discharging performance at high and low temperatures, and longer life.
The decrease of ambient temperature in winter is mainly due to the increase of electrolyte viscosity of lithium batteries and the slowdown of lithium ion
activity insidethe batteries, which results in the decrease of discharge (output) current of the batteries and the decrease of start-up power of the batteries.
Charging or discharging batteries at ambient temperatures below - 20 C will greatly reduce the battery life and affect power output and endurance mileage.
Therefore, it has become a common practice in high-end electric vehicle industry to install heating system for lithium batteries in electric vehicles to pre-heat
and protect lithium batteries before charging orstarting (discharging). In addition to heating the car, the heating system of electric vehicle is mainly designed
to meet the requirements of normal use of batteries in low temperature environment.