Lead Acid Battery - 2 Cells No Float

[KendallP]

So I picked up a new (to me) rig from family last weekend. It had been sitting at the BIL's place for several years. He started it occasionally, but never kept it plugged in.

2 of the 3 group 29, Interstate, hybrid "deep cycles" tested in ok shape and sharpened right up after a good 3 hour hammering with my beloved Chicago Electric, Harbor Freight, 20A manual beast.

I'm afraid to do anything with the 3rd battery because the SG in one of the cells reads at the top of the red and another reaches just to the top of the entire float before... floating it.

At 60F, the rest of the cells read...

1.310
1.310
1.325
1.300

Of course I don't know their baseline, but that's pretty high. After the hard equalizing, the other 2 came up to a healthy 1.275, give or take, in all cells.

And the resting voltage of this battery is 12.67, measured with a quality multimeter.

I've never seen such a thing. Seems like 4 of the cells have taken the brunt of the alternator charging and are now overperforming.

None of the cells had low electrolyte. BIL said he never added water. Never touched 'em.

I'm kind of afraid to equalize it because I'd be concerned about overstressing the other 4 cells. But maybe that's what it needs?

Or...
.

[BFL13]

The higher SG (more acidic) sitting there for so long could have eaten plate so maybe not much left? If you got 1.3 up top where the hydrometer can reach, what was the SG like near the bottom all those years sitting there?--it would be higher. You might remember my tipping the 27s days to de-stratify them.

I have run mixed banks of various combos no problem while camping, then recharged them at home by type to their own specs and combo again for floating them if not enough floating chargers handy.

I have done two 6s and a 12, three 12s and two 6s, four 6s and a 12, and for lots of AH two 12v T-1275s and four 6s. Then I got two 12v AGMs and mixed them with the two T-1275s. Now I am back to four 6s in the Class C and two 12s in the TC.

I did try it without mixing batts, using one set for inverter only and the other set to run everything else. That worked with two solar sets one on each set of batts. It wasn't a good way because the "RV" set would get low and there was still plenty of AH left in the inverter's set, but no way to get at those AH to run the furnace. So back to mixed bank to spread the wealth.

What is the converter in the new to you rig?

[KendallP]

BFL13 wrote:
K, hope the new rig works out for you.

Mex will have to answer about why the high SGs. You will know this, but IMO put a load on that battery to see if it holds up under load, even if its voltage isn't too bad with no load. ( Same with the other two just in case of course)

If it does hold up, it would still make me nervous to bank it with the other two for very long.

Hey B,

Thanks! Me too.

Yeah, I sent a PM to Mex. I figured this question was well above most of our pay grades. I'm sure we'll see him when we see him.

Unless someone smarter on the subject than the two of us has another idea, then I'm inclined to agree with ya'. I was thinking maybe there could be a way to replace the electrolyte, but the whole thing is just too odd. I can replace it for less than a hundred bucks and then sleep at night. Of course I'd prefer 3 identical batteries "new off the truck," but... it seems a shame to just get a core rebate on those 2 with such good SG figures.

EDIT: Come to think of it, with just the 13.x volt float charge spread across three batteries, I probably wouldn't be too concerned about that weak player messing with the rest of the bank. I think the larger concern here is total capacity and fewer minutes of generator noise at the campground. Peukert... and so on and so forth.

But now what do you think of the 2 GC2s plus 1, 12V G29 idea?

The GC2s would be easier to restore following successive 50-90% cycles. And they should fair better with solar. I'd just have to hammer the 29 a little more when I got home to combat our good ol' PCL (progressive capacity loss.)
.

[KendallP]

2oldman wrote:
Old batteries. Get rid of them and try AGMs

Thanks 2oldman,

Yeah, I'm well versed in AGMs vs FWCs. AGMs have their place, but I got over 10 years out of my old group 27s and a 6300 series converter because they could be safely equalized... and the rig was always plugged into shore during storage.

And then only 10 years because the property owner stopped paying the power bill without letting me know. SG numbers were still beautiful just beforehand.

That said... my BIL did replace the Cat starting batteries with a pair of these babies. I won't know their condition until I can do a load test. A 500A load tester has been on my list for many years. Perhaps I'll take the plunge rather than driving the rig into the shop. Though I might be concerned that one of these monster batteries could blow the thing to smithereenies.

With the cranking power specs of these suckers, part of me wants to sell one off and utilize the storage space for a 4th GC2. Worst case... I could always start the Cat with a boost from the house bank.

(Brainstorming) OR... since it's an AGM... with low self discharge and no concern of spillage...

I could keep one of them in a separate compartment as a jumpstarter and just top it on occasion. I guess I could start with seeing how easily just one of those AGMs turns over the Cat with a multimeter monitoring things.
.

[KendallP]

wa8yxm wrote:
You can attempt equalization but you have 3 Group 29 MARINE/deep cycle that's about 280/290 amp hours and about 71 usable before rapid aging sets in.

Go to a pair of GC-2 (about 220 Amp Hour) about the same price as a pair of Group 29's and you get 220 amp hours 110 usable before rapid aging sets in
And you can parallel a Group 29 with them (yes you can) in case a battery goes bad..

Hey J,

Long time. Thanks for weighing in.

Believe me, I've considered GC2s. They would always be my preference where height is a consideration along with even numbers. My old rig also had room for 3, so I went with 3 27s. I never considered 2 GC2s plus an additional 12V in parallel. Most intriguing idea.

I guess my stumbling blocks would be...

1. My 2-29s appear to be in excellent condition according to the SGs

2. I'm more concerned about max storage at the campground vs. life expectancy. Though again... your 12V hybrid parallel idea is something I hadn't considered before. I'm such a creature of symmetry, I would have that to overcome.
.

[2oldman]

Old batteries. Get rid of them and try AGMs

[Lynnmor]

If you can get by without the third battery, simply remove it.

[BFL13]

K, hope the new rig works out for you.

Mex will have to answer about why the high SGs. You will know this, but IMO put a load on that battery to see if it holds up under load, even if its voltage isn't too bad with no load. ( Same with the other two just in case of course)

If it does hold up, it would still make me nervous to bank it with the other two for very long.

[wa8yxm]

You can attempt equalization but you have 3 Group 29 MARINE/deep cycle that's about 280/290 amp hours and about 71 usable before rapid aging sets in.

Go to a pair of GC-2 (about 220 Amp Hour) about the same price as a pair of Group 29's and you get 220 amp hours 110 usable before rapid aging sets in
And you can parallel a Group 29 with them (yes you can) in case a battery goes bad..