battery bankd advice/thoughts

I was doing some maintenance yesterday on the batteries and checking electrolyte levels as well as condition of each cell with a hydrometer. I have one bad cell in a bank of two group 27 batteries. All other cells are in good shape. So, 1 bad cell out of 12. Its not totally dead but its headed there.

Common wisdom is that when you replace one battery you replace them both, I hate to do this- ( sort of like Subaru's advice you replace ALL tires when you replace one). So, I am going to llive with this for now, I guess. i assume I am simply sacrificing total capacity though I dont know how much or if that would tend to degrade the rest of the system---if it at all. I dont know why that might be the case but i am all ears for any wisdom any of you might have.

thanks

rick

Rick, you've probably already done this, but I'd refill the low cell with distilled water before charging it again. Then, try to get it back to full strength with a slow charger such as the Battery Minder. I think I'd separate the two batteries to do this so that you're working on just the one that is going bad.

Once fully charged, if you can get it that way, connect the batteries together again and maybe you'll be fine for a while. Keep an eye on the low cell. If it drops again, the battery is simply bad.

And yes, I'd replace BOTH if you need to replace either. A bad one is going to hurt the good one. Connected together, they're both going to have the voltage of the bad one and it will probably create a constant drain on the other.

- Jack

I fear the cell is just getting worse. I totally drained both batterys earlier this year when I accidently pulled the emergency brake while having it parked for a week. ( think I fried a couple of magnets as well.) The other battery shows good on all cells but I may just bite the dust and replace them both-give the good one to my brotherinlaw for his bass boat. Costco had group 24 interstates when I stopped in today and I may go back to them over the 27s as I, rarely, need that much reserve for what I have been doing. It would save a little weight as well. Still- those batteries are only four years old and were still working pretty well. Trailer has been sitting for five weeks with no trickle charge on it and I am still showing about 12.54 on the multi meter which is about 90% full charge. But, I will try what you suggest with a battery tender, though the one I have only puts out around 3 amps.

thanks Rick

3 Amps is enough to bring a low battery back up to full charge if it CAN be charged. Give it a try.

However, four years is a pretty good lifespan for a lead-acid battery.

- Jack

I would pull the bad one. If you don't need all the power one good 12v battery should work fine. It's a thought.

UPDATE:

Well after doing all the appropriate things I went camping but the batteries were dropping faster than I liked. i actually took my 2000 watt generator along for the first time and used it twice in three days after just running, mostly, the fan. Not what I like. So- seeing as both batteries are not holding up to snuff I think it IS time to replace them both. That said, the season is over for now, pretty much, for us so I guess i will wait until after the new year, or spring, before I replace them. No sense in "starting" the warranty until I need the batteries and the old ones I can leave on battery tender for raising or lowering etc. At present, Group 27s are just about 10.00 more than 24s , but, they are tight in there and I may just go back to two 24s to make things simple based on what we tend to do.

Thanks for the input.

Rick

4 years is a long time, maybe some people get 6 years, but after that good luck. Likely, for anyone reading with similar issue, the bad battery is draining the good battery down. Even with a new battery, the old bad will pull power from the good. Almost better to just use the one good battery alone. You could buy a used battery that is not "bad" and maybe get another season out of it. Batteries need to match as far as voltage.
Definitions: run in parallel means both batteries are hooked to the camper positive to positive and negative to negative. You can hook as many batteries together like this. The results is 12+12 = 12 volts.
run in series means first battery negative connects to ground, positive connects to second battery negative then second battery positive connects to camper. Similar how you stack D-cell batteries in your flashlight. The result is 6+6 = 12 volts.
A solution to this bad battery/good battery issue is to use two 6 volt batteries inline. Together they make 12 volts, but if one is bad it cannot drain the other, it just makes both add up to less. (say one is 5 volts and the other is 6, then you just get 11 volts max, not 12. Also your two-12 volt batteries wired parallel where one is 11 and the other 12 volts, this does not make 11.5, but rather, the 11 volt tries to charge itself off the 12 and then both become 11.) Run the 11 volt and 12 volt in series and you get 23 volts, but that is too much for your 12 volt camper, so get two 6 volt batteries.
Downside of two 6's is if one goes bad, then you cannot use the good one alone, as 6 volts will not run the camper, but that is unlikely to happen, usually one goes bad and drops, and you can run camper on 10 or 11 volts for most things.