UPS Battery pack: Homebrew replacement?

[rhyds]

My APC 750XL has a suspected iffy battery (doesn't seem to last very long on battery, and the red battery warning light comes on every now and again) and I've seen that replacements are in the £100+ region...


...The thing was when I pulled the current battery out "for a nose", I saw that it's simply two 6-cell lead acid batteries lashed together. Is there an easy way for me to work out the capacity of the batteries used in order to find a couple of a similar size/capacity for replacement? The wiring seems easy enough, it's just a case of finding the right batteries.

[CyberNerd]

we replaced one withsome batteries from cpc CPC | CPC - Over 100, 000 products from one of the worlds leading distributors of electronic and related products.
just check they are correct voltage/current and the unit is out of warranty

[CPLTD]

We can supply you with the replacement battery for this model for £95.00+vat With Free Next Business Day Delivery.

[FN-GM]

I know John uses alarm batteries, ask him he might be able to help

[Geoff]

DIYing the batteries will invalidate your insurance, should you accidentally cause a fire and burn the school down.

[Domino]

My gut reaction is somethign along the lines of EEEEEEEEEEEEKKKKK


..and as Geoff mentioned your insurance will be boned

[FN-GM]

DIYing the batteries will invalidate your insurance, should you accidentally cause a fire and burn the school down.

For the sake of £100 its not worth that really.

[rhyds]

True, but £100 for what amounts to two small car/bike batteries bolted together (quite literally) is a bit annoying. I doubt even SLA batteries are that expensive...

[stratisphere]

Not that I do this here (no really... i dont) but the 2 UPS's I have at home both came from knackered batt's. So i did some DIY and hooked up 2 car batteries to them.

Not only do they work perfectly now but they also last longer. Sure it aint pretty... but since when have UPS's been pretty?

To be honest, I agree... UPS batteries are a rip off. Especially the higher up the model chain you go. But as far as risk goes, it's best to pay the £100 and play it safe.

(Please note, by me saying this, I am in no way saying using car batteries or alternatives are more risky. Nor am i saying real UPS batteries are safer. I'm just saying school's can usually afford to be a little more... official)

Edit: BTW to work out the capacity of a battery you either do:
- Search for model number on battery... bound to be some info on the net somwehere
- use some expensive kit,
- or charge it up, put it on a meter and drain it (electrically... not physically!)

[rhyds]

Stratisphere: That would have been my plan at home. Especially considering I could get hold of a few tractor batteries.

Looks like it's the £100 job for me, but i'll wait untill it's propper dead first (i've swapped it to powering a few switches now, so if it does conk it's not a terrible problem)

[CPLTD]

Stratisphere: That would have been my plan at home. Especially considering I could get hold of a few tractor batteries.

Looks like it's the £100 job for me, but i'll wait untill it's propper dead first (i've swapped it to powering a few switches now, so if it does conk it's not a terrible problem)

lol like i said fella £95.00+vat from us with FREE delivery ,

[john]

Some of the baby UPS's use farily small generic batteries that CPC and RS sell. You can just take the wiring off your current ones and wire in the same fashion matching the wiring exactly as done by APC. They are all fairly similar in style but its the capacity etc of the battery that is key, a lot of APC ones seem to be individually rated so you may find the info on them and then a bit of google and your sorted.