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Old 02-05-2018, 06:07 PM
ron45 ron45 is offline
Join Date: May 2014
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Default got myself in trouble again....

We are off grid [since 83 ] and I have a batt. conundrum.

During the addition of another kw of PV's we ran into an issue w/ our battery bank. During the back and forth the T.S. guy [who is very nice and knows his stuff ] told me `there is no way to connect 12 batteries in a straight line and get a 24v. series parallel battery that charges all batts equally.'

I'll admit he probably has a much better chance of being right than I do.

I'd try to work this out on my own but I have nearly terminal dyslexia and a fading short term memory, and anything to do with working out spatial relationships puts me into grid lock.

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Old 02-07-2018, 12:36 PM
blackpowderbill Male blackpowderbill is offline
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Location: Madison County, NE Georgia
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I hear you. While at Xerox there was a UPS room full of batteries for back-up. I'd have to go in ever few months and check connections,liquid levels and specific gravity, fans and intake shutters.
What a PIA and rats nest of cross connections it was. This battery bank was charged from 2 ends as I recall.
So as not to use one side that had to run juice down the line to the end. It feed from both ends.
Having once been downwind of a plate of biscuits and squirrel gravy does not make you Daniel Boone. KD Williams
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Old 02-11-2018, 11:48 PM
MichaelK Male MichaelK is offline
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Location: Sierra foothills
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Since your system voltage is 24V, I assume that you have three strings of 6V batteries in series, is that correct.

Your friend is very correct in saying that you'll get unequal charging.

You have two workable options. You can rig disconnects so that you can individually charge each string separately, so they all get fully charged, then equalized, separately. You'll need a good hydrometer to make sure the equalization process is complete.

The second option is to change from whatever battery you're using to a 2V L-16 (Trojan is SIND-02-1990). Then you'll have a single string of batteries with more total capacity then you've got now. Trojan also makes a 4V battery that might work for you, (SIND 04-1685) but those weigh 367 pounds.

Good luck!
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Old 02-12-2018, 08:25 AM
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12vman Male 12vman is online now
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I agree with blackpowderbill. Make your 3 strings in a row. (assuming 6 volt cells) Series connect all 3 pos/neg connections along each side and feed/draw from opposite ends. Make all of the interconnect cables in the strings as identical in length/gauge as possible and be certain of good connections. *Solder if possible*. Keep the series connection cabling for the strings the same. Connections, length and gauge are very important!

I have 8-6 volt cells series/paralleled to achieve 12 volts in this fashion. I added fused connections between each series connection between the cells as a safety factor. This also provides a break in the system to open the circuit so to check an individual cell if one is suspect of being bad..
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