marc780 wrote:
If you have a volt ohmmeter (also called a multimeter) you can check the battery and alt quickly. Just set the meter for "12v DC" and put the probes on the battery.
Engine off battery should be AT LEAST 12.4 V. 12.6 or greater is better.
And now start the car and let it idle first for two or three minutes, (more accurate). And now put the probes on the battery again and your meter should read at least 14.0 volts. If it is less than 14 then either your alt is bad or belt is slipping, so change them. (Acceptable range = 13.9 - 15.0 volts, engine running at idle)
Your numbers are off.
Car Off: Voltage can be as low as 11.5
Idle: 12.5+
Driving: ~13.5+ (expect lower if your using air condition, head lights, etc)
I have been monitoring my voltage via my passport 8500 for atleast 4 years. All of the cars in my family have the passport 8500 all set to voltage mode, so i'm very confident in the numbers.
...As for the battery - it is very possible that it has a bad cell. I had a similar problem with my yellow top battery, and replacing it did the trick. It was covered under warranty.
The alarm definately does drain the battery. Even with a deep cycle, optima yellow top, i only get 1 - 2 weeks before it goes dead.
If you have the car in a garage, get a battery maintainer. It trickle charges the battery so its always ready to go