Refilling sealed lead-acid battery?

[NiHaoMike]

I don't think I'd want to charge it with the original charger and that would be a hassle since typically batteries like this are charged by the equipment while it is plugged in.

The nice thing about LiFePO4 is that 2 cells have more or less the same charging voltage as 3 lead acid cells. You can also get a balancing BMS to be sure, although I'm not sure how common are 2S LiFePO4 balancing BMS.

[bob91343]

I would prefer to get a lead-acid replacement.  The old battery has a price tag of $4.95.

It's not an important issue; I don't need a battery operated voltmeter and this meter isn't all that useful.  I just thought it'd be nice to have it work as original.

[tautech]

Digikey still has Cyclon cells for sale:
https://www.digikey.com/catalog/en/partgroup/cyclon/3500

[Gyro]

I have an old HP voltmeter that came with a rechargeable battery.  Of course the battery is old and toast.  It's made by Gates and has three lead-acid cells.

I wonder if I could break into them and add water to make them useful again.

Nope, waste of time and effort as the lead plates will be too badly sulphated.
As they say; it's dead Jim !

Cyclon cells are very unlikely to lose any water. They tolerate very high internal pressures and their vents are set accordingly. The only likely failure mode is sulphation due to long term discharged storage (even then, they are pretty robust and can sometimes recover with long duration charge - until they start pulling current). Treat them right and they will last for literally decades!

They're well worth replacing like for like - as tautech's link.

[BradC]

They're well worth replacing like for like - as tautech's link.

I've been using them where possible to replace standard SLAs in hard to get at, critical or expensive equipment. I absolutely love them.

Yes, they are expensive, but they just seem to keep going, tolerate accidental abuse better than any lead acid I've ever worked with and seem to have a tiny self-discharge characteristic.

Worth the price of admission.

[james_s]

You can get them from lots of places, the link I posted sells them for around $8 each, shop around though, they have been made for decades and are widely available.

[bob91343]

Nothing for less than about $40, not worth that much to me.

[james_s]

$40 doesn't seem like much money to fix a piece of gear. Hard to get any kind of battery pack for much less than that.

[Craftsman]

Sorry for being a bit late to the game but I've actually had good success so far with refilling SLA UPS batteries!

I, like others in this thread, have popped the covers off, refilled the cells, and then charged the battery only to find out that the results were far less than expected with little to no capacity recovery.  I concur with the general consensus that the batteries were sulphated and therefore, just watering the battery at this late stage will do little to revive the battery.

Before giving up on these batteries, I decided to take things further and attempt to desulphate the batteries.  I initially used a Foxsur 8A charger with a repair mode which is known to have good success in desulfating car batteries.  After a few short hours, the Foxsur charger signed it was done.  A quick test of the capacity showed that little capacity was added as the Foxsur ended too soon to do much good (it has a termination point when the battery's voltage hits 15.85V which is fine for a regular flooded battery but these AGM batteries get to 15.85V too quickly).

Therefore, I decided to try an Alastair Couper design desulfator readily available on the likes of e-Bay - I upgraded the components and corrected the known published flaw (one of the timing capacitors for the 555 was the wrong value).  Initially, to just hooked up the desulfator and let it run and recharged the battery every few hours as the battery ran dead. The constant need to recharge the battery grew tiresome.  So, I decided to connected it to a 12V float charger to power everything and let the whole thing run for days rather than hours.    After a week, I removed the float charger and recharged the battery fully to see how long the battery could power the desulfator and got a bit more than a day which was a massive improvement over a few hours.  I reconnected the float charger on the battery and continued desulfating for another week (so two weeks in total) and did another discharge test and found that the battery now lasted 2 days and a bit.  I connected the float charger back on for another 2 weeks and the discharge test now resulted in 4 days.  After each discharge test, re-watered the cells.

After reconnecting the batteries up to the UPS, the run time displayed on the UPS is now the same as a brand new battery.  I completed a discharge test on the UPS and the numbers were very reasonable.

I've only completed this on two SLA batteries and both came out great.