Battery issue

[Bman Gtz]

If my car sits for more than 2 days without being started, the battery is dropping down to about 10 volts, yet when I boost it, it goes right back up to 13.5 give or take and I can turn off the car and fire it back up. I had it tested before and there is a minimal drain but I am thinking the battery is on it's way out, how would I confirm this. It's a optima yellow top, about 5-6 years old. Any help would be greatly appreciated, thanks.

BMAN

[Koots]

It sounds like it's getting weak or it's not getting charged properly.

The best way to test a battery is a simple battery tester, one that puts a load on it to see how quickly the voltage drops. You could do it using a multimeter, cut off the fuel to the engine and crank it while you or someone watches the readout. An okay battery will drop down to 10-11 on my old school battery tester. I know because I ended up going through 3! sets of batteries in my diesel K5. Each set cost me nearly $250, so I was testing each damn battery I got LOL

[pghturbo88]

If my car sits for more than 2 days without being started, the battery is dropping down to about 10 volts, yet when I boost it, it goes right back up to 13.5 give or take and I can turn off the car and fire it back up. I had it tested before and there is a minimal drain but I am thinking the battery is on it's way out, how would I confirm this. It's a optima yellow top, about 5-6 years old. Any help would be greatly appreciated, thanks.

BMAN

Charge it up fully, pull it, and have someone load test it. Many parts stores will do that for free. If it passes the load test, next step would be to put a voltmeter across the battery with the engine running to validate alternator output. If it is near 14 volts, alternator is okay. If the battery passes these two tests, then you have a phantom load somewhere (light staying on, etc.)

[berettaboi]

you can also charge it up and leave it unhooked, see if it has dropped to 10 volts with nothing hooked up to it... that's the dead giveaway.

if it keeps at 12.7 volts or so after a few days of being unhooked, then you may have something drawing power in your car while it's off.

[DTMAce]

I know mine can be pulled down too low to start the car if it sits for more than 2 weeks, but I know there is a drain there all the time.

[Bman Gtz]

Yeah, most cars all have a small drain, I know mine did from previous tests, but I am just wanting to fix the issue is all, thanks for the help guys. Gonna yank the battery out and have it tested.

[Bman Gtz]

Well, I let the car sit for almost 3 weeks with the battery disconnected, went to storage today, plug her in and she fired up so I don't think the battery is the issue otherwise it would have lost power from sitting, so now I need to figure out what is draining it. Has anyone ever heard of an alternator draining it while sitting? The car sits for a few days and loses enough power for it not to turn over, then I let it sit for a week or so and it ran down to 2 volts. Any help would be greatly appreciated. Thanks.

[berettaboi]

it is a possibility. You can eliminate some stuff by yanking a bunch of fuses, and leaving the batt hooked up. if it stops draining, then something on one of those circuits is pulling some "key off" amps. I havent tried, but i'm sure you could toss a ammeter between the fuse points, while the fuse is yanked, to complete the circuit, and see what has some power running through it. there is a certain amount that is allowable i think too.