The owner manual says, that to charge the 12V battery, it has to be disconnected from the car.
My solution is to disconnect only the negative terminal, and charge the battery in the car. (leaving the positive terminal connected).
I just make sure, that my charger, which is grounded doesn’t touch the body of the car.
It works well.
The reason I have disconnected the negative instead of the positive is because the negative terminal is in the open, and has only one wire attached to it. The positive terminal has many wires attached to it.
In my case, the 12V battery is new, replaced by the previous owner, who didn’t charge the original 12V battery, and it has gone bad.
It is not too cold here yet, so I have the negative cable disconnected from the 12V battery.
The 12V battery is fine in the cold temperature. It will not freeze.
