12 volt battery location and charging

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mindmachine

Well-known member
Joined
Mar 15, 2014
Messages
502
Location
Ohio, USA
KMP647 said:
I tried searching but couldn't find the posts on this topic
I am buying an i3 Rex that has been at the dealer for months
I always like to top off the 12 volt battery on any newly purchased car
Where is it, and is ther any thing special about charging it .
I have a deltran 3 amp trickle charger

Thnks in advance
Click to expand...

Charging the 12 volt battery directly is not recommended as it is charged when you charge the HV battery using EVSE. Even if the 12 volt battery drops to low to activate the computers, BMW says to plug in the EVSE to charge the 12 volt and not to try charging it directly. The 12 volt is also charged when the vehicle is in ready mode and while being driven via the HV battery.
 
The owner's manual says you can damage the car if you try to charge the 12vdc battery! IOW, DON'T! Now, I suppose if you disconnected it, you could, but not sure what effect that would have on things like many of your presets which may be held because of the 12vdc battery.
 
It is under the passenger side frunk velcro panel, but way back towards the firewall. Not easily accessible. And as others have said, not a good idea to put a charger on it. You can toast the capacitors in the EME if it kicks on the DC/DC converters while you are charging it, if your voltage is higher than it is.
 

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