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Anthony

Many x 7Ah batteries

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With prices souring and availability on the decline, I was wondering what the limitations of the old reliable 12V 7AH could be.  I have heard that there is a limit of 3 parallel strings of batteries.  I know that the cycle limit of the 7AH will not be great, but at R5,000 for 8 x 48v strings yielding a 50AH it could be an option. with monthly checks of the batteries to insure consistent charging.    Replacing a few 7ah batteries every year is cheap enough.

We all want omni's or pylontech, but at the moment beggers can't be choosers...   Just wanted to know if it is a viable temporary solution.

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@scrarfussi  Good suggestion, but I had some Royals and the Axpert just didn't want to charge them AT all.  Went to some 12ah's that worked and onto Omni's.  Now I am looking for replacements.

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Posted (edited)

There are UPSes that use small lead acid batteries in long strings (96V I think) and do well enough, but for backup purposes, not for daily cycling. So in principle doable, but the cycle life is not going to be that great. 200-400 cycles according to some random specsheet I googled into.

I think the biggest issue is going to be when one cell goes short circuit and that string starts to pull current from the other 7 (plus charge current), cooking the rest of the cells until one of them blows up like a balloon and then potentially explodes.

Odds of that happening is 8 times greater than with a single string...

Severity of things going bad... also much worse.

Risk = likelihood x severity.

I agree with @scrarfussi, if you're going to cheap out, cheap out on the Royals. Though of course... you may not be able to find stock of those 🙂

Or.... design a RAIB... random array of inexpensive batteries 😛

 

Edited by plonkster

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On 2020/03/16 at 2:56 PM, scrarfussi said:

it works out expensive in my view  rather buy the royal batteries 105ah at R1500 or so 

R6000 for 48v 100ah   vs R5000  

and simpler wiring and less monitoring of the batteries 

You have a source? Gauteng preferably? my google fu is not revealing something with stock at the moment.

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