UPS/Inverter Qs

[AdeV]

Questions to those more knowledgeable than I....


I have an APC 3000XL uninterruptable PSU I scored for a low price, as it had been dropped & all the plastic smashed off. I particularly like the fact it will run my entire server cab - which draws ~650W continuous - with ample runtime.

However, I'd quite like to significantly enlarge the battery bank, to massively boost the runtime, and also to load it up with the other half of the office + lights (basically, everything except the kettle). That's all well & good, but I've been advised that one shouldn't really increase the amp-hour capacity of the battery bank beyound about double (for an APC XL UPS) its maximum recommended, because the charger wouldn't cope.

My question is: If I wired a massive battery bank into the APC - and then separately wired up a charger, linked to the old Lister set to the appropriate voltage (24 IIRC - so whatever the appropriate charge voltage is for that size battery) - would Bad Things happen to the APC? Or would it cope with the over-voltage?

I'm guessing that, in normal use, it'd use some of the incoming power to recharge the batts, and pass the rest straight through to the consumer side; wheras I will be running the inverter continuously & pumping the volts directly back into the batteries.

Or - am I better off buying a dedicated inverter unit; and if so, which one (would like ~ 3kwatts of peak capacity, although the whole office should normally run on about 1/3rd of that).

Thanks in advance!

[mobile_bob]

the xl series are made for extended battery pack use, iirc you can connect up to 9 additional packs to the unit.
it will just take forever to recharge using the internal charger but it can be done.

i have one of the 3000xl units and it works fine for me

i also have a few of the 1400xl units which i have had working on a 225amp hour battery bank, which is well over 10 times the 17amp hour
internal batteries it had internally.

i  found it would take a couple days to recharge the batteries buy would work,  i also recharged with the 555 on my trigen and the 1400 xl could care the less.

for a while i had 4 of the 1400xl units connected and running off the same bank, this sped up charging off the mains of course, showing they
can play together and recharge no problem.

efficiency is about 87% which isn't great, but the waveform is near perfect sine wave. with the bigger battery bank i would expect
about 5kwatts of surge for about 3 seconds before the unit faults out and shuts down.  all of the units i tested would do right at about
1.8 times rated output for surge for a full 3 seconds.

i would say go for it

bob g

[camillitech]

Him AdeV,

I really know nothing about this subject as, being 'off grid' I prefer the dedicated inverter/charger route but I did read this recently, which may be of help/interest

"The XL versions allow additional external battery packs to be attached. The UPS in this case needs to be informed how many external battery packs are installed so it can perform the functions outlined above, otherwise you shall experience the same issues of premature shut-down. To configure the number of external battery packs you need to use the APC UPS management software. Unfortunately APC do not specify their battery packs in terms of voltage and Amp-Hour, but you can work them out with a little Googling. You shall need to select the number of APC batteries that is the closest match for your bank."

It came from here http://www.navitron.org.uk/forum/index.php/topic,15204.msg170344.html#msg170344

Seems to know what he's talking about.

Good luck, Paul

[cujet]

While not the same,

I have an APC "back UPS pro 1100". (It's a substantial 24V UPS, not a common cheapie, with 2 very large batteries)

I removed the internal batteries, ran the wires outside the case, and hooked it up to a 24V, 44AH aircraft battery. Works great.