Simon wrote:I got the following answer on the question why the battery is not 100 full at departure after preconditioning and why it is not taking power from the charger at all times: (it came from BMW headquarters)
” Required precon. power can be higher than charging power, depending on temperature, SoC and charging supply. Thus SoC can go down even if the vehicle is plugged in! … but will be recharged. some details: at cold temperatures (<0°C), a precon. power of up to 5kW is required. Charging with the standard cable at charging power “low” only delivers ca. 1,4kW, even at “high” only 2,8kW. And: at nearly full SoC, charging power goes down <1kW, no matter if plugged in to a AC 7,4kW charger or even DC charger. This is part of the charging characteristic of every Li-Ion battery.
- SoC can go down up to ca. 10%, if it is very cold/hot and charging power “low”.
- Timing: e.g. at -10°C, preconditioning will start ca. 30min before departure time with 5kW, then go down to 3kW and keep the vehicle warm 15min after departure time. Charging will proceed afterwards (if still plugged in) until the battery is fully replenished.
- All this is independent of automatic preconditioning at departure time or manual activation and charging timer / immediate charging etc.
- Exception: at public charging stations which unlocks after full charge, charging cannot be restarted.
Thanks for that information, it's very useful and makes complete sense of what I've been noticing and struggling to understand.
If your EVSE cannot supply sufficient power for the pre-conditioning phase the power extra is drawn from the battery.
- When preconditioning my standard UK EVSE draws the maximum 10 amps, the rest is coming from the battery
The consumption during pre-conditioning when cold is likely to be much higher than can be supplied from a standard charging connection.
- That fits, most mornings so far in my ownership the ambient has been below 10 C and the battery is not full when leaving.
If you do draw from the battery, because the SOC is nearly 100 %, charging rate is low, so the energy drawn from the battery takes a long time to replace.
Seems like another good reason to have a 7kw EVSE.