Battery question

Hello,
I am just starting off with my solar setup. To begin with I have a 100W panel and charge controller (best to get my head around everything before getting any bigger!). I will also be starting 12V DC out only - to power some garden/shed lights and some device charging points.

I have come into possesion of some old UPS batteries. There seems to be 16 small 7Ahr batteries in series of 4 then run in parallel. On the first set of 4 I get a reading of 24.2V.

My question is: what should I do with them!! I am thinking of striping them back and configuring in parallel. This would get me over 110Ahr @12V which would be ideal. Is this a bad idea? That is, should I just get one battery of 110Ahr instead of 16 @ 7.2? Will these be hard to maintain? As they could be anywhere from 2 to 6 years old, should I just recycle them?

Finally, each batch of 4 terminate at an Anderson connection. I don't have the tools at the moment to crimp news ones so would a 50Amp terminal block (connected correctly) be OK for parallel?

Thanks

wheresthesun said:

On the first set of 4 I get a reading of 24.2V.

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It would help if you identified what batteries you have. Are they 6v batteries?
What are the individual voltages of each battery? If they are similar enough, they can be used together to make a larger battery bank. But if some are new, some are old, they will cannibalize each other and eventually fail.

You first need to determine what you have. If you are able to better describe it here, someone will likely be able to let you know how to best use them.

MisterSandals said:

It would help if you identified what batteries you have. Are they 6v batteries?

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They are 12V 7Ahr batteries. There was 16 of them (all identical - sealed Lead Acid), combined, in the UPS

But if some are new, some are old, they will cannibalize each other and eventually fail.

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Yeah, this is my main worry!

wheresthesun said:

They are 12V 7Ahr batteries. There was 16 of them (all identical - sealed Lead Acid), combined, in the UPS

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If you can separate them and individually charge them and test them, you can get a good idea which ones are good. If you have 4 in series at 24v, its likely that some/all/most are not usable.

If you can get a few that charge and appear to hold a decent charge, then you can build a bank with them. At 2-6 years old, it will be hit and miss. The ones that have been abused (kept below 12v for extended periods, or discharged well below 12v) are probably toast.

I should add, its definitely worth seeing if you have enough to work with. I've used dozens of these over the years for quite a few projects.

If you can charge them up to 12.8v (or close), let them sit for a day. The ones that discharge down to 12.1v or less are pretty much ready to be recycled. If they hold 12.3v it may be usable. 12.4v an up probably useful, especially in numbers.

Similarly, any that hold a surface charge after a day, need to be able to hold up to a reasonable load without the voltage dropping quickly (this should be obvious).