One of the (written) requests I had was to check the EV battery and also the 12v Aux battery (when I had the BMW i3, lots of issues were caused by the 12v aux batt).
So the reports came back that both batteries are healthy, no issues and they gave me some print outs.
Knowing that I'd be away for a week, I didn't want to leave the EV battery flat so when I drove it last time I used the Charge mode quite often getting the EV range up to 5 miles.
Back a week later, unlock the car but it goes completely dead, dashboard dark yet I could still hear the AVAS sound!? not even the door locks were responsive, locked the car with the key and went to find a neighbour to lend me an extension so I can charge it.
Accessed the boot from the inside via the little flap, left the EV charger plugged in for 2 hours but nothing.
I then removed the boot cover to access the 12v battery and connected a smart charger - it showed 3.6v charge!!
Ultimately I had to remove the 12v battery and leave it in the garage to charge... couldn't use the car for almost 2 days.
Calling the dealer they said it's normal because the ICE doesn't charge the 12v battery..
So I still don't understand how the report came completely fine and the auxiliary battery was healthy and then reached such a low charge - did I do something wrong? what could've caused this in just a week?
but better than the inconvenience of not being able to start my car because my 8 year old battery had let me down I guess.