6V battery maintenance on RV

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zombieapocalypsegame
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6V battery maintenance on RV

Post by zombieapocalypsegame » Sat Apr 22, 2017 7:04 pm

Hey all

My RV's been beeping periodically of late. It's the smoke detector telling me the battery is really low. We haven't been using it so I haven't been too worried about it and had other priorities to fix first. I've also got a 12v solar panel on the ignition battery, so I know I can start the thing. It's the house batteries that are the issue.

But, with summer approaching it's getting hotter here in Texas and I can't sleep with that beep outside our window if the window is actually open. It's roughly every 5 minutes, maybe 10. Haven't timed it but it's frequent. And my wife is a super light sleeper, so I'd never hear the end of it. :awesome:

It's not the first time this has happened. :( Last time, we were living in the RV several years ago and had begun beeping while we were plugged into shore power. The batteries were just ~4 years old at the time but were dying from poor maintenance on my part. Those were Trojan T-105 deep cycle 6V house batteries wired in series for 12V service. Expensive mistake at the time.

Since we were in it full time, rather than messing with trying to fix the old ones I replaced the batteries with exact same model. These current ones are now a little older than the originals, but they have been maintained much better overall.

That said, I put a multi-meter on the batteries after taking them out. I got 5.88 and 5.85. What is normal on a 6V? I see a 12v battery would be @ roughly 25% with a 11.73 rating I have from them combined. So they are definitely discharged but hopefully not completely gonzo.

I typically have the battery disconnect thrown so the house batteries weren't getting juice FROM anywhere, but there is ONE thing that still sucks down charge even in that scenario which is the smoke alarm itself. But even when I re-connected the house batteries by flipping the switch, they wouldn't charge. I left it plugged into shore power (110V household not 30A like at a camp) for about 3 days and that did nothing.

Here they are prior to removing from the RV
Image
6V Deep Cycle Trojan T-105 batteries

I am wondering if heavy corrosion on the series cable is to blame.

You can just barely see it in this photo - the battery cable on the left battery negative post is heavily corroded / rusted under the securing nut. I don't recall ever seeing it like that before. If that is providing heavy resistance, that might explain why the batteries won't charge.

I'm going to hit the cable with a wire brush thoroughly to clean it up while I have a wall wort charger on the battery pair directly to see if that helps. If not, I'm going to try de-sulfating the batteries. Nowadays I have a nice box of Epsom salt in the garage.
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Re: 6V battery maintenance on RV

Post by MPMalloy » Sat Apr 22, 2017 7:22 pm

Question: How expensive are the cables?

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Re: 6V battery maintenance on RV

Post by NT2C » Sat Apr 22, 2017 7:28 pm

You could have corrosion up inside the cable under the insulation. The easiest thing now is to just replace it, clean the terminals, and get the batteries charged back up. Since they are in series you charge them as a pair, like you would any other 12v battery, just using the positive on one and the negative on the other.

If you can't find the cable local just drop me a note with the length and gauge and I'll make one and pop it in the mail for you. I make all my own cables.
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Re: 6V battery maintenance on RV

Post by gundogs » Sun Apr 23, 2017 8:37 am

A reading of 5.85 is very low,about 20%---fully charged should be about 6.5
If batts are 6-7 years old they may be shot.
Have you charged them yet?

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Re: 6V battery maintenance on RV

Post by raptor » Sun Apr 23, 2017 8:46 am

A charged 6 volt bathery should have a reading of at least 6.25 volts.

You should remove the connections and use a wire brush or sand paper then clean them. Then clean themail post connectors. Then reattach them.
You can then try an charge the batteries to see if they hold a charge.

You can also use a hydrometer to see if one cell is dead.
FWIW I get only about 4 years out of my marine deep cycle batteries.

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Re: 6V battery maintenance on RV

Post by Dooms » Sun Apr 23, 2017 11:44 am

We have extra 6 Volt batteries at work for swapping into various machines and used to have trouble with them dying on us prematurely. Speaking with the battery vendor we were told to get them off the cold concrete floor and to use a 6 volt Deltran Battery Tender. Ever since we did that we've had no issues.

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Re: 6V battery maintenance on RV

Post by zombieapocalypsegame » Mon Apr 24, 2017 10:38 pm

These batteries are wired in series in the RV for 12v configuration, and are charged using the shore power connection. The solar panel on the roof is only temporarily wired to the starter battery, and the cutoff switch for these (house) batteries is usually thrown off to prevent drain from them.

So, I won't use a 6V tender on them. If anything, I would connect the RV to shore power to keep topped off. Now that they are on my workbench, I can use my 12v charger in my garage but only if they are again wired in series and meet 12v specs. So, the cable again becomes my primary focus.

That said, I may only need to clean off or swap the rusted/corroded connector wire, or I might need to desulfate the batteries if they are in fact discharged too much.

Do 6V deep cycle batteries have any difference regarding the desulfation process than typical 12v car batteries? i.e. using epsom salt in solution to recharge the cells?

Thx
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