It takes some of the power from the charger to heat the battery further. Necessary if temperatures are around or below zero (Celsius)
If the battery pack is too cold the heater will switch on automatically.
If the battery pack is at or above 10C the heater will not switch on.
While the heater is on, the battery is heated up to around 17 to 20
Intelligent battery geating instead is mostly there to avoid ‘cold-gate’, whereby rapid charging will be severely limited in the first few minutes until the battery pack is at or above 12 Celsius and then as the battery heats up ( to around 30 to 40 Celsius) speeds will quickly increase