P85D / P90D have "Set max battery power" option to heat the battery (more power available) but also useful to get rid of regen limit. For other cars, you can toggle the use of the battery heater when regen is limited by using Range Mode OFF. On Range Mode ON it doesn't use the heater and takes a serious long drive to gain regen from self battery heating from discharge. Having a heavy foot here helps get it done faster. On range mode OFF, the battery heaters starts once you drive (or of you pre-heat the cabin), and uses 5kW max.