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Old 05-14-2016, 11:02 PM   #1
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Battery down under 5v- what happened?

Trying to solve a mystery I just discovered with my electrical system.

Some background:

- brand new 12v 'true' AGM deep cycle battery (UB121000)
- recently replaced power converter, including DC board (PD4655)
- converter appeared to be working flawlessly
- DC system appeared to be working flawlessly, we dry camped with the new battery/converter for 3 nights and finished with about 1/2 charge on the RV gauge which seemed good for how much power we used.


After that weekend, we stored it, and I also plugged in a 12v solar panel trickle charger (sunforce 50022 5 watt) that I used on my old trailer without any issues. On this new-to-us trailer, the only 12v socket is the TV antenna jack, so I (perhaps foolishly) plugged it into that thinking it would work as my old system did, and pushed the button on the jack, thinking that would 'open' the circuit between battery and solar. Typing it out it sounds awfully suspicious and naive, but you tell me.

Next time we came out to the trailer, the battery is functionally completely dead. Seemingly no power at all except to light up the LED indicator lights on the DC board.

Today I took my multimeter to it and was very surprised to see it reading only 4.8v! I unhooked it to take it home to try and diagnose, and noticed a divot with some green stains on the outer case of the battery, directly under the neutral line, as if it had been very hot and melted a small divot.

Now unhooked to anything, it seems to actually be gaining power...? It's up to 5.1v in about 2 hours of sitting idle.

The solar panel is a few years old and has some wear and tear, including a few areas where the outer wire cable has stripped and kinked (but not to expose bare wire, only the dual wires contained within the outer casing). It's putting off about 9v when exposed and just a few millivolts when covered.

What could be the issues? Things I've considered:

- a short in the DC system. I sure hope not, this will be harder to resolve.
- a bad battery/cell. But it's brand new and worked great for a short while.
- the antenna jack won't work for this and somehow the solar panel is to blame?
- DW left the fridge door open to try and keep air moving in the fridge. We didn't see any lights but maybe there's something else drawing?
- mystery draw in the trailer just happened to drain the battery completely. But would a normal draw like a LP detector draw it down below 5v?

I haven't yet charged the battery, nor taken it to get checked at an auto parts store. Also I didn't think to manually check the DC fuses in the panel, however none were lit up, even though the DC board green light was on.

Any ideas what I might be facing here? Is my new battery screwed already? Thoughts on next steps?
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Old 05-14-2016, 11:33 PM   #2
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Quote:
Originally Posted by Eazy View Post
- DC system appeared to be working flawlessly, we dry camped with the new battery/converter for 3 nights and finished with about 1/2 charge on the RV gauge which seemed good for how much power we used.

1/2 Charge on the panel is most likely less than 1/2 charge on the battery...they're not all that accurate.

After that weekend, we stored it, and I also plugged in a 12v solar panel trickle charger (sunforce 50022 5 watt) that I used on my old trailer without any issues.

5 Watts is nowhere near enough to recharge. The most you can expect out of that is to maintain once charged.

Now unhooked to anything, it seems to actually be gaining power...? It's up to 5.1v in about 2 hours of sitting idle.

That's somewhat normal and indicates you had a draw on it prior to disconnecting it.

It's putting off about 9v when exposed and just a few millivolts when covered.

Again, nowhere near enough to recharge a depleted battery. You'll need 14V or more to completely recharge. Seriously consider spending $100 or so for a good smart charger if you're going to dry camp like that very much...it's cheaper than new batteries.

But would a normal draw like a LP detector draw it down below 5v?

Yes, that alone will hurt a battery in a week or so if fully charged, much less one that's half charged or less.

I haven't yet charged the battery, nor taken it to get checked at an auto parts store.

Along with not discharging below 50%, charging ASAP and keeping them that way will keep them happier longer.

Any ideas what I might be facing here? Is my new battery screwed already? Thoughts on next steps?

Maybe not toast, but the life has probably been cut pretty good. Next steps...get it charged, get a good charger, keep it charged, and disconnect it when not in use. Also, don't rely on those panel lights. While not extremely accurate, I just use a multi meter and check voltage once a day..generally after we've been away for a while with minimal draw on the batteries.
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Old 05-16-2016, 03:32 PM   #3
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Thanks for the reply. Sounds like you're thinking it just simply drained due to normal draw from LP detector and such. If so, I suppose that's better than having some kind of chronic short. I'll get to ordering a smart charger and a battery cutoff switch.

What about the small cable-shaped divot on the battery casing? Nothing to worry about?
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Old 05-16-2016, 05:41 PM   #4
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I would see if I could bring it back and have it replaced. It sounds like an internal battery problem if you can see physical signs of overheating on the outside of the battery.
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Old 05-16-2016, 08:31 PM   #5
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If your solar panel is putting out 9v that is not going to maintain your battery. The normal draw from the CO/Propane detector etc would not be covered by that solar panel either. You need at least 13v with some amperage to maintain the battery.
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Old 05-16-2016, 08:47 PM   #6
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do a google search on AGM chargers... AGM batteries have special needs that a regular charger does not always provide...

you have harmed the battery, but it might come back for you to get some use, but never back to original spec's

How about taking a picture of the damage you see on the case???
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Old 05-16-2016, 08:48 PM   #7
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Those small solar trickle chargers are nothing more than a gimmick. The do not produce a high enough voltage or enough current to do anything. As mentioned above, it would not even operate the CO/Propane detector. Dry camping for 3-4 days on one battery is a challenge. Once you get the battery charged back up, I would take it to a battery dealer and have it load tested. The battery lights on the control panel are a best guess only.
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Old 05-16-2016, 09:59 PM   #8
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Quote:
Originally Posted by Eazy View Post
Trying to solve a mystery I just discovered with my electrical system.
Today I took my multimeter to it and was very surprised to see it reading only 4.8v! I unhooked it to take it home to try and diagnose, and noticed a divot with some green stains on the outer case of the battery, directly under the neutral line, as if it had been very hot and melted a small divot.
IMO, if the battery got so hot as to melt the case, it would take an extreme amount of amp load which would have popped breakers and fuses. since everything is working, it seems an internal short would be more likely. Simply, killing the battery over time, would not melt the case.
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Old 05-16-2016, 11:00 PM   #9
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Get a real voltmeter and monitor the battery during charging and use. Get information on AGM batteries, max voltage drop and charging voltage which are different than lead acid batteries.


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Old 05-17-2016, 10:30 AM   #10
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The craftsmanship clip-on DC/AC amp meter (about $49) at Sears is one of the most useful tools For finding out what your current flow is.
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