How low should the voltage on a car battery get after sitting over night?

It will stay around 12 volts, if you let it sit for a 3 or 4 weeks it may not start it takes a certain amount of voltage to run the computer.  more

ok, sorry for being rude but ignore the dumb *** answers here and message me the actual issue, the problem is that you question is irrelevant, what are your symptoms, a battery will naturally discharge over time as it ages as will a fresh battery charge itself with time,  more

There are 6 cells in the standard battery, and each one puts out 2 volts. 2 x 6 = 12. well, actually more like 12.35, but 12 is close enough. To charge it, you have to put in than those 12 volts, so normal charge is 13.8 volts.  more

sounds like your battery has a bad cell or just can't keep a good charge anymore.  more