Loads of 12V 20Ah SLAs - what to do?

[dovadil]

Hello humans on the Internet,
Please help guide me though this new world. I have watched a ton of content and read loads on the subject, but I would really appreciate some opinions from this community.

I have been given ~25x 12V 20Ah AGM batteries (https://www.mouser.de/datasheet/2/95/dow01425630501-910184.pdf).
They are in various states of function and health after sitting for a while.
I would like to create a large-ish battery bank from them and also hook it up to a Solar Charge Controller to charge them up and keep them in a float charge state when not utilised.

So I have a couple questions:
1) What is the best practice to evaluate their health?
2) Research has shown me that parallel configurations with 3 or more batteries can result in them degrading each other. How would one hook them up to use the highest number of batteries to create a large battery bank without running into the above issue? (I am not against configuring them to make a 24V system)

Bottom line, I am looking a for a solution to make use of the most amount of the batteries I have, in a not too complicated system.

My budget on the other side will afford me ...
- 2x 100W 12V panels
- ~30A 12/24V MPPT Solar Charge Controller (Epever)

Thanking you
Dovadil

 

[MisterSandals]

They are in various states of function and health after sitting for a while.

You should see which ones accept a charge and stay over 12V for more than a few hours.
Recycle the ones that cannot hold 12V.

Now how many do you have?

Lets say 20 are good.

20 x 20Ah = 400Ah (only 50% usable because cannot discharge more than 50%)

I would like to create a large-ish battery bank from them and also hook it up to a Solar Charge Controller to charge them up and keep them in a float charge state when not utilised.

Great, lead acid batteries love this. Its also very cheap and easy to do.

My budget on the other side will afford me ...
- 2x 100W 12V panels

You should look for big cheap panels on craigslist. Most folks find panels for $.50 per watt and sometimes much better. If you have a location, maybe someone can suggest a good place to find some cheap.

 

[Substrate]

If you are serious, you're going to have to spend some cash to quickly cull the bad ones.

The fastest *consumer level* way of doing this with those agm's, would be to let a very smart charger quickly identify the duds (instead of simply trying to charge trash like most other would), and present that to you in a easily identifiable way:

Tecmate-Optimate 6 Ampmatic 5A charger

This is the fastest consumer-level way I know of to identify those that are not worth spending any time on - and of course giving those that have some sort of quality left a decent charge. Charge each one *individually* at first.

You are correct that anything more than 4 batts in parallel is typically hard to keep balanced. So aim at identifying the good ones, and putting no more than 4 in parallel.

Seems like you have a plan - but to figure out if you have been given a total load of trash, or something worth playing with, you'll want to look at the Tecmate-Optimate charger first.