I think I damaged my batteries :-(

[daveola]

So I have a large battery bank.  10 group 8D AGMs.  2 banks of 5 in parallel for 24V.

And I just did some rewiring to put in some new master switches and to make it easy to charge off the bus battery bank.

But I think I really blew it.

Suddenly today the bank can barely hold much of a charge, and the genset surprised me today by coming on when the solar panels should have been giving us enough juice to be running just fine.

The genset came on a few more times this evening - usually the genset only has to run once a day, if even that, thanks to the solar panels.

So I took a look at the bank and realized that I screwed up and didn't tighten the bolt down on the last battery in one of the series.  Unbelievable screwup.  There was some contact, but I don't know how much, the nut was at the end of the threads of the bolt which was loosely threaded through the battery terminal.

So the question is - what is this most likely to have damaged?

Right now both sides of the battery bank are reading the same voltage, so it's not out of balance.

Is it possible that only one battery or only one side of the bank is damaged, and what's the easiest way to find out, short of pulling out all 3/4 ton of batteries and load testing them.

*sigh*

Not a good day.

[daveola]

To clarify the wiring, see attached image:

[Oonrahnjay]

... Is it possible that only one battery or only one side of the bank is damaged, 

    If there's damage, I think that's probably right.  Did you reconnect the loose bolt and give the bank a good charge?  It may be that you had enough of a good connection to allow the batteries to feed but not enough to take a charge.  It may be that if you can make a good connection on all the terminals, and can get a proper charge, it will work OK again.

what's the easiest way to find out, 

    Can you get to the individual terminals, like to disconnect them without pulling the batteries out?  If you can, you can load test them that way, or you can try individual battery charging.   But I'm guessing that you don't have access to the individual batteries or you wouldn't have asked. 

Not a good day. 

    No, but I hope that it turns out better once you've worked through it.  Good luck!

[bevans6]

I don't see why any of the batteries should be damaged.  It sounds like they weren't getting charged properly but your automatic systems took them off load before they discharged too far.  Have you done a charge cycle with the loose terminal fixed?  I would just do that, do an equalize charge, and see if they behave normally.  I have a feeling that they way you have them hooked up isn't optimum, but then again I have never been able to figure out the right way to hook up batteries in the first place.

[gumpy]

Fix the loose connection and let them sit for 24 hours to equalize on their own. They will even out. Then charge them normally. You should be fine.

[TomC]

You lucked out in that the first battery in the bank was the loose one. If any, maybe that one battery is bad, but I doubt it. Tighten all, charge all. Good Luck, TomC

[TomC]

When I had my engine turbo'd, and since it was out of the bus, I had the starter replaced. The ground wire from the solenoid was not tight and causing miss fire, not starting when hot. I just simply tightened up the terminal, and perfect starting ever since. Amazing how well electrical stuff runs when terminals are nice and tight.

[daveola]

Ugh.

I've reconnected it tightly, and once the charger is done I can watch the battery voltage dropping .1V every 15-30 minutes, when I'm only using about 1-2A of 110V from the inverter.

This is the wrong time financially for me to be replacing the battery bank.

I can get to each of the leads, but I don't have a load tester and I thought that load testing usually takes some time, so to load test each of the 10 batteries while in the bus would mean parking the bus somewhere next to a load tester for a couple days?  Is that right?

[gumpy]

If you want to check them individually. Shut everything off and disconnect them for 24-48 hours. Then test each one with a volt meter.

And by disconnect, I mean unhook each one from the string so it's stand-alone with nothing drawing on it.

[daveola]

I might have to do that, though we're boondocking, so that means no power for 24 hours.

Or maybe I could cut the bank in half.

Does only one battery going bad really enough to bring everything else down?  Shouldn't I see an unbalanced amount of current going into one battery to charge it up, thereby discharging the others?  Because I checked amps on the leads I could reach, and they're all fairly even.

[Oonrahnjay]

I might have to do that, though we're boondocking, so that means no power for 24 hours.

Or maybe I could cut the bank in half.

Does only one battery going bad really enough to bring everything else down?  Shouldn't I see an unbalanced amount of current going into one battery to charge it up, thereby discharging the others?  Because I checked amps on the leads I could reach, and they're all fairly even. 

      It's only a WAIG, but there's a pretty good chance that - if you have a damaged battery - that battery is showing a high resistance to charging.  That switches off "modern" automatic charge-then-trickle chargers (or other staged chargers).  After all, most of your arrangement is in parallel.  But there are so many posibilities for the details on this about all we can do is guess until you get some testing done.  But, yeah, take half your bank, wire them parallel/series to make 24V and you should be able to run on that, as long as you don't have a bad battery in that group.

[Iceni John]

Because FLA batteries have such low internal resistance, it's vitally important that interconnection cables between batteries have exactly the same resistance.   This means making them exactly the same length, crimping their lugs with a good circumferential crimper, and checking their individual load currents with an accurate DC clamp-on ammeter.   Seeing five batteries in parallel makes me nervous  -  there's too much chance of imbalance within that amount of batteries.   The folk at the Northern Arizona Wind & Sun forum have some very definite ideas about paralleling too many batteries!   SmartGauge has some excellent suggestions for interconnecting batteries the right way:   http://www.smartgauge.co.uk/batt_con.html

One possible way around having too many batteries in parallel is to do what I've done.   I have two completely separate banks of house batteries (each bank charged by its own charge controller that is powered by its own array of four PV panels), and each of their outputs is fed through a 250A Schottky diode before being combined to the DC load center and inverter.   This way, if one battery in one bank goes bad and draws down the entire bank, it cannot suck power from the good bank.   The voltage loss through Schottky diodes is much lower than the more common silicon diodes that can absorb almost one volt  -  that's why they have such huge heatsinks!   Another incidental benefit to having two separate battery banks is that I can replace one bank of batteries at a time instead of all eight batteries, or even use different batteries in each bank (the charge controllers can be easily reprogrammed for virtually any type of battery).   Now that's redundancy!

Just an idea,
John

[luvrbus]

I have about the same hookup only with 6 batteries 2-12 v runs my question of the day is I have a 24v to 12v drop down for the 12 v stuff,should I run it through a Vanner or will the 24v to 12v converter draw evenly from the battery bank

[gumpy]

I have about the same hookup only with 6 batteries 2-12 v runs my question of the day is I have a 24v to 12v drop down for the 12 v stuff,should I run it through a Vanner or will the 24v to 12v converter draw evenly from the battery bank

I don't understand your setup. You said you have two 12v runs.  Are you saying you have three parallel banks consisting of two 12v batteries wired in series for a resulting 24v output?

[luvrbus]

I have 3 -12v batteries in each run wired in parallel then tied in series for 24v that is the way I got the bus and it works but I am going with 8 batteries so It can be a straight 24v