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UPS battery voltage

Posted: Fri May 01, 2009 1:16 pm
by mab
I see from floydsters post that I'm not the first to use an old UPS as a cheap truesine inverter. :?

I'm currently using a powerware 750va UPS as it uses a 24v battery (which matches my main battery bank), but would like a more powerfull inverter.

I see from nino500's reply to floydsters post that APC's 1500va unit uses a 24v battery pack. does anyone know of a larger ups that uses 24volts before I buy an apc1500va unit?

cheers

mab

Posted: Fri May 01, 2009 10:20 pm
by ChrisB
I've got a Compaq 2kva one here but it if loaded to the max it draws silly current (which of course it would) so larger Kva invertors generally run on a higher voltage to try to keep the current down.

I had a nice 3kva one that ran on 72v system of a couple of packs of 12ah Yuasa's and it made a huge difference on discharge current on the batteries.

ChrisB

Posted: Sat May 02, 2009 10:15 am
by nino500
APC 3000 and 5000 both use 48v, which is quite easy to set up by running two 24v alternators (one to each half of the pack), but at least one needs to have an isolated ground (marine ones usually do) Or you could could fabricate an insulated bracket.

I've never found anything larger than the 1500 on 24v though.

Nino.

UPS voltages

Posted: Sat May 02, 2009 4:50 pm
by mab
Thanks guys, may keep an eye out for one of the compaq units...

That's sort of what I thought - as you say there's good reason they go for higher voltage battery packs at higher powers.

The reason I want 24v is that that is my main battery voltage. I was wanting a larger inverter mostly 'cos it'll handle the switch-on surge of various loads better than my 750va unit (in theory). The largest sustained load I was planning on using would be the microwave - which is rated 750w but draws 6 amps (i.e. nigh on 1500va).

cheers
mab