Battery Question

[waygard33]

A friend gave me a Deep Cycle battery that he bought new in 2002 and never used. It was left just sitting all this time, never charged.

I charged it and after sitting for 3 days, it measures 12.42 volts (about 75%) with no load. (After charging and waiting about 6 hours, it measured 12.68)

My question is: What does this mean. How long should a battery hold nearly the 100% charge. In the case of this battery, it would be my backup and it would be at 75% before I even hooked it up. Is it toast or is it done?

Thanks for your help,

[wavery]

A friend gave me a Deep Cycle battery that he bought new in 2002 and never used. It was left just sitting all this time, never charged.

I charged it and after sitting for 3 days, it measures 12.42 volts (about 75%) with no load. (After charging and waiting about 6 hours, it measured 12.68)

My question is: What does this mean. How long should a battery hold nearly the 100% charge. In the case of this battery, it would be my backup and it would be at 75% before I even hooked it up. Is it toast or is it done?

Thanks for your help,

Check it again after 24 hours and let us know what it reads. I'm actually surprised that it took a charge at all.

The main thing is to check to see if it is full of water. If it's low, top it up with distilled water (only). Charge it again, wait 24 hrs then post your reading.

The best way to check the battery is cell by cell with a hydrometer. If it has one bad cell, it's toast.

Think of a 12v battery as 6 - 2v batteries wired together (because that's exactly what it is). If one of the 2v batteries is bad, it will just continually discharge all of the others.

[tlhdoc]

I would use a 3 stage smart charger with a desulfication cycle.  I would run the desulfication cycle a couple of times and then charge the battery.  I wouldn't count on the battery being good, but it is worth a try.

[waygard33]

Thanks for the advice. The fluid level is good. I'll charge it again and see what happens. I'll let you know how it goes.

[waygard33]

I charged the Battery to 100% again and 12 hours later, the voltage is 12.5.

With no load, I figure this is about 80%. Doesn't sound good.

What kind of charge should I expect on a good battery, a few days after charging and then left to sit in the truck until needed on the camping trip? How close to 100% should it be?

Thanks again,

[austinado16]

12.5v appears to be about 90%, which seems good.  If it's bad, it's bad so you can try it out and who knows, maybe it'll be just fine for how long you plan on being "out" and what you plan on running.  Won't cost anything to give it a test run in camp-driveway.

Here's a battery level chart I found online today.  I actually printed a version of this out (minus the specific gravity info since I can't check mine) and used clear packaging tape to tape it to the top of my battery box.  No more guess work.  My PUP has a neat little analogue voltage meter built into the converter panel, but I think I'll add a little digital one like one of our members posted pics of a few weeks ago.

[wavery]

I charged the Battery to 100% again and 12 hours later, the voltage is 12.5.

With no load, I figure this is about 80%. Doesn't sound good.

What kind of charge should I expect on a good battery, a few days after charging and then left to sit in the truck until needed on the camping trip? How close to 100% should it be?

Thanks again,

OK, now that you have a base reading, give it a few days and check it again. If it stays about the same, you should be good to go. If it drops to about 12.2 it may be week at best.

After letting it sit for a couple days, try putting a load on it, like a simple 12v light. Leave it on for about 12 hours, then take a reading and do the math.