Recondition or reuse end-of-life SLA batteries from a UPS?

If you take the top panel off (it's probably glued down) you will likely see a row of rubber vent caps underneath. If they have dimples in them then the cells have probably vented and dried out. If the cells are ok, I've heard of people successfully rehydrating them.

I took a look at a couple of mine, found that they had vented but a couple of cells had also died so game over.

Oh yeah.Thanks for pointing this out!

You might have helped me determine the next steps. It depends on how hard it is to get those lids off. I'm sure they're glued down pretty well.

Maybe I'll take the approach of whatever ones I can inspect are candidates to keep.

I'll look into what is involved with rehydrating. But I suspect the "sealed" part of "SLA" will make that a non-starter for me. Instead, maybe I can get 2 or 3 that haven't dried out yet. Then I can use them for something else until they do.

Mine had 10 dabs of glue around the edge of the cover, so it levered off without breaking.

If you pop the rubber cap off there is about a 5mm diameter hole into the cell, so you can rehydrate with a syringe or straw.

I'm guessing that the battery charging circuits in these UPS units aren't up to much. I've found that most of the batteries fail within the first year or so of use. Would be interesting to find out why they are so unreliable.

Here is what the dabs of glue under the cover looked like on one of mine:

I think they're cheap batteries packed into poorly ventilated boxes. So they get cooked.

From what I remember when looking at UPS designs a while back, there are offline and online types. The offline type keeps the batteries out of service until needed. (Except when doing the testing cycle.) Online types keep the batteries in the inverter loop so that there is less downtime. The tradeoff is that they see a lot more ripple and degrade faster.

I believe most consumer models are offline types, but maybe a few keep the battery active, leading to earlier failures. Shrug.

Thanks! That gives me some context.

I think after I get the swaps done, I'll look to see if one has a lid that is more willing to come off. Removing the lids will be much easier once I know where the glue is located.

I dunno. I suspect most if not all of these will end up in recycling. But I really want to try and salvage a couple.

I've seen some people keep the UPS electronics but then use an external car battery instead, with much better results.

lol. yeah. I'm not into having science fair projects around the house.

But, maybe in the lab.

I'm going to have to try this, open it up.  Carefully of course, bad acid to deal with. 

I inherited a nice UPS that didn't charge the batteries.  It had six 12V SLA batteries in it.  I pulled it apart and found the one bad battery, tried to bring it back to life with an automotive battery charger.  That didn't work.  But now I have 5 (mostly?) good batteries.  I put one in my cheaper under-desk UPS when that battery failed.  Now I have 4 good SLA setting there, probably slowly going bad.  Yes, I could buy 2 new batteries, but the six battery UPS was way too loud to use in my home.

My experience is that they are rarely salvageable for anything useful.

If they've been sitting in a UPS, they would likely suffer either from being dried out and bubbled up internally where adding distilled water doesn't do much. Their grids may also be malformed from corrosion that happens when sitting on float all the time.

If they've been sitting in a dead UPS, then they would probably be sulfated to death ... which is also mostly irreversible.

The gelled/AGM construction of SLAs generally preclude any service even though you could try. I know I have tried the same from batteries from fire-alarm panels etc but not been successful.

(Incidentally, many low-cost UPSes nowadays are "line interactive" which is basically an AVR + offline UPS. These usually keep their batteries floating all the time.)

- Gough