Originally Posted by insane79
i got a battery charger from the dealer today, will charge it up when i don't use the car often, is 13.8v reading from the battery good?
13.8V is what's called the "float charge" voltage for lead acid batteries. I'm going to assume you had the charger plugged in when you got that reading?
Anyway, yes, that's fine. If you're driving, you may get in the 14V range (depends on the alternator's MO, it's not going to be constant voltage in a bimmer). Anything down to just under 12V is probably acceptable. Not sure what the threshold for a low battery warning is. A deep discharge will be somewhere around 10 or 11V