SLA Battery stuck at 10.5 volts

I have a maintenance free SLA battery (12v)

From a UPS not old than 2 years

Yet the battery problem came along .. I tested it and found it was showing somewhere around 10.6 - 10.7 volts .. I thought maybe putting some new distilled battery water in each cell might help so I put around 3-5 ml liquid in each cell

(Enough to see floating liquid above the dried cell which I saw while opening the cell caps)

I didnt knew that these battery were meant to always sealed and not to be added water

Since I charged it to 13.8 volts (standby use said on battery label) overnight .. nothing happend

Then I charged it to 14.9 volts 2 days later couple of hours (Cycle Use charge voltage on battery label) while opening the caps to release the gases …. Then charging 13.8v overnight temaining open battery

Nothing happen.. the next day (see image)

Only the cell was hot and bubbling sound could be heard

Still atick at 10.6v after disconnecting the charger

Charger current limit was set at 1.35 A (written on battery label)

Battery is still producing bubbling aound after disconnecting charger for about half an hour now

However .. the short circuit current it still pretty good .. about 5.7 Amps from the battery at 10.5 volts

Please help me how can I fix this if there is even a fix .. or now this battery is a complete trash and I discard it ?

I really want to repair/fix this battery

Please do reply and help me

Top Replies

Gough Lui over 2 years ago

It's rubbish.

Any lead-acid battery that sits discharged even for a while is likely sulfated and thus will have severely diminished capacity.

VRLA cells are designed sealed. There is no service to be performed. At end of life, they are to be recycled or disposed.

- Gough
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Shreyas_Kumar_103 over 2 years ago
But then how is it able to output a short circuit current of more than 5 amps ... and then recover to 10.45 volts after removing the short wire?
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dougw over 2 years ago

The characteristic voltage of a lead acid cell is 2 volts or 2.1 volts, so you likely have one dead cell. I have never seen a way to refurbish an SLA battery, however this guy seems to have found a way...try it at your own risk...

https://www.google.com/search?q=sla+battery+sufuric+acid&oq=sla+battery+sufuric+acid&aqs=chrome..69i57j33i10i160.9201j0j7&sourceid=chrome&ie=UTF-8#kpvalbx=_WhFnZL6dJ7ClptQPtpaimA4_6
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Gough Lui over 2 years ago in reply to Shreyas_Kumar_103

5A for a cell of that size is pretty bad. Normally it's well over 100A for a healthy battery.

You may have a bad cell, but much more likely it's just bad. High current into a short doesn't mean much energy flow - power is current * voltage. Shorting an AA alkaline cell can get you close to 5A too but that's hardly amazing.

UPS cells that sit on float for all the time can suffer from internal plate corrosion instead of sulfation. Either way, neither are recoverable conditions.

- Gough
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JWx over 2 years ago

As dougw mentioned - it seem that there is a problem with one cell - maybe it is shorted, so other cells are overcharged and bubbling. Had the same with car's battery - it was able to provide moderate current (not typical charge loss scenario), but at 10.5V the starter wasn't engaging... Repurposed it as bird chaser power supply.

I was working on UPS battery revival for some time - adding water, charging and discharging (even published project here with 555 and some load for combined charge/discharge cycle) but to this day got only very unbalanced battery - some cells overcharged, some not going to be fully charged.

If you have already caps removed, you can measure voltage of individual cells - dipping one multimeter contact in electrolyte (contact may be damaged by the acid - maybe some graphite electrode would be better [retroffited from old AA battery for example])
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