Voltage low when running 11-12amps

[JRust]

What do you guy's think my car battery is running low on juice. After driving for a while eventually it just won't start up again after stopping somewhere. The battery is only about 5 months old. But after being charged all night it still shows only 12. I've heard it sould be about 14 when fresh. I had a buddy check out the Alternater on one of those charger systems. He said he thought the alternator looked o.k. Might be a little tired but he thought the problem was probably in the battery. So do you think my battery maybe has a bad cell in it? Looking for possibilities

[Joe Ricard]

Actually you may want to check the transmission ground strap. Clean up both ends or just plain replace it. Then pull the big can off the fuse relay panel inthe engine compartment clean off any corrosion. Then go to the starter connections. If that doesn't help proceed to all the common ground points and clean up those connectors(all brown wires). Lights will be brighter gages will read more accurate etc.
BTW 12 volts is just fine engine not running. maybe 1 or 2 volts higher with engine running measured from the battery terminals. If you want to pull your hair out check voltage at the fuse panel. With any corrosion the volts will be lower there.
The alt makes like 55 amps give or take.

[jabb]

With the battery disconnected it should read about 12.2 - 12.4
on a digital volt meter. If it is 12 you might have a problem....
You can take the battery to a garage and have them load test the battery this will quickly tell you if the battery is godd or not....
New batteries do fail.

[Kevin Powers]

how's the belt tension?

[Dave at Pelican Parts]

12.65V (after the "surface charge" is gone) indicates a battery that is "full". 12.0V indicates a battery that is discharged, or maybe even worse. (I.e., dying.) This is measured across the battery terminals themselves--not the clamps, not the wires, but the terminals.

Charging voltage is around 13.5V - 14.5V. The charging system has to output a higher voltage than battery voltage to get the electricity to flow into the battery.

--DD

[JRust]

Problem solved I'm an idiot. Thanks for the post Kevin. I didn't check the tension of the belt when I read this afew days ago. Pretty much forgot about that. Was putting on my new coil tonight. I relocated it on the fan shroud. Anyway I happen to drop a bolt up front & in searching for it. I found the cursed belt sitting unattached down below. Put it on & what do you know I'm up at 14amps with the car running. Guess I'm not to bright.