Is my battery dead?

Question

I have a 1995 Pontiac Bonneville. The battery is only two years old so I dout that is the problem. I have been having to get my car jump started, the battery has been completely dead after leaving it sit overnight. The alternator is charging the battery because i can still start my car 4 hours after i have been driving it for 15 minutes. What could be draining my battery? I also pulled out the fuse the controls the chime and the radio. thanks

Answer 1

A common misconception alternators will not charge a dead battery,alternators require a min of 10.5 volts to overcome the internal resistance of the stator and diodes.Get your battery charged first,with a volt meter across the terminals - + check voltage with the engine running just above idle,with the headlights on it should read about 13.8 to 14.5 volts anything higher that 14.7 volts the alternator is at fault(shorted stator)anything below 13.8 to 13.0 volts it is the regulator.Some regulators are external but most are internal they can be replaced but sometimes it's more cost effective to replace alt.A simplified load test for the battery is after it is fully charged,turn the headlights on for 5minutes and then try to start the engine,if it starts it's not the battery.
REMEMBER ALT'S DO NOT CHARGE A DEAD BATTERY.

Answer 2

Even brand new batteries can be bad. Does EVERYTHING work on the car? You may have a system draining your battery. Does the light above your head work? Has someone unplugged the horn? The horn relay will still draw juice. If you can, get an ohm meter and remove the negative battery cable. Hook the meter between the battery and the cable. If you have a draw, it will show a full 12 volts. Open the door to check if it doesn't show a draw at first. If the draw goes away when you shut the door it is the battery. If you still have a draw, remove the fuses one at a time until the draw goes away. The fuse that you pull that kills the draw, is the system pulling the battery down. A wire could be shorted to ground or something is turned on but doesn't work. Anything left plugged into the cigarette lighter? Do you have a power Antenna? Unplug it. It will not effect your radio.

Answer 3

Best place to start is a charging system diagnostic, like $25, and go from there. This does a load test on the battery, checks the AMP's drawn by the starter and checks the voltage output of the alternator.

If these all check out OK, then you have a parasitic draw somewhere and I'd recommend a shop that only handles electrical repairs since this is all labor to find the drain and fix it. Most "grease monkey" shops can't do it fast enough and it should never take more than two hours to trouble shoot a parasitic drain. One guy under the hood, one guy at the "fuse box" and presto, a diagnoses in about an hour. (Labor times two guys equals two hours labor.)

Good Luck!

Answer 4

Have your battery checked with a Hydrometer after it is charged up. A single bad cell in a battery will sometimes cause it to function properly as long as it is used regularly, but after letting it sit for 12 to 24 hours it will be dead.

Answer 5

Sounds like your battery has a bad cell and isn't able to hold a charge anymore...take it to AutoZone or someplace like that, they will test it for you for free.