'Priming' old UPS batteries

[Mike Tomlinson]

In article , Sparks writes

Maybe the OP wants a long run-time?

[Martin Evans]

APC's designers ought to read up on what voltage you use to maintain a charge on sealed lead acid gel cells. Their battery packs would last a hell of a lot longer if they did, but that's hardly good business is it? In the application they are designed for the batteries ought to last for a good 10-15 years. Abused as they are by incompetent design I am surprised they even manage to give service beyond a few weeks.

[Andrew Gabriel]

I suspect this comes about because of the rapid full recharge required so you can soon sustain another power failure, possibly combined with lack of capability of the electronics to switch between cyclic and standby mode charging (if indeed that is the situation). But yes, it would seem to be a design fault. I have SLA batteries which are 10 years old and still have their full capacity in other equipment.

[Simon Barr]

Are you sure? The following is from a Yuasa tech document for their SLA batts.

NP batteries are designed to operate in standby (float) service for approximately 5 years, based upon a normal service condition in which float charge voltage is maintained between 2.25 and 2.30 volts per cell in an ambient temperature of approximately 20C (68F).

Thats 5 years at an ideal 20C. How many UPS are operated at that? In my experience, none. All UPS get hotter than that, I just checked three here and found that one was 25C, another 28C and a third 34C, and that's their internal temperature without the invertor running.

Surely that must reduce the battery life, though the document doesn't say by how much.

[tony sayer]

And AIUI their charging voltage is temperature dependent, but they do have some sort of temp compensation when charging don't they?....

[B Thumbs]

We have lead acid batteries over 50 years old on standby alternator sets over 50 years old and still fit for the purpose. They are onto at least their second charger, though.

[Martin Evans]

The Yuasa specs for volts are a bit on the high side compared to other manufacturers but APC, certainly in every UPS i've checked, don't seem to compensate for temperature nor is the voltage particularly well controlled in the first place. Go to the right manufacturers and you can get a predicted 25 year life from absorbed mat batteries - i've experience of cells, albeit on open racks that are now in their

14th year and still at close to 100% capacity - the chargers are properly designed though. If you need fast recovery of charge then by all means up the volts for a short period but to continually overcharge is just plain criminal.

[Stefek Zaba]

Yeah - that's for the 'general service' range. They also do a longer-life range - NPC, if I remember aright - for which they claim maybe double that life. I'd look up chapter and verse, but rswww.com is refusing my login credentials right now...

Stefek

[bigcat]

tell us more.

NT

[tony sayer]

Theres quite a lot of useful info on the Exide site. Just bought a serious amount of these and they should hopefully last me into retirement;)..

[Simon Barr]

Cheers, I'll take a look at those.

[Stefek Zaba]

NPC as it turns out is the name for their deeper-discharge range, but there's other variants claiming longer life, from Yuasa and other mfrs too. If you pop over to rswww.com and navigate their Products along the route 'Consumables -> Batteries/chargers -> Lead Acid Batteries', there's plenty of technical data once you pull up particular items. (You need to register to read the datasheets).

HTH - Stefek