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I would think its possible to do this when the normal battery cost about 500 bux to replace. I have several large forklift batterys that i can use if they would work with it. I am worried about the UPS will freak out cause the battery is so big. I know alot of them check the battery and if they keep charging it they will think it bad ( a forklift battery can hold a hell of alot of power and take a long time to charge) and thats what i think might happen if we try this here.

I know all about voltages and what nots so thats not an issue. The UPS is a APC, I dont know what model it is the front cover is missing.. but it is a big as 5U rack mount thats deep as hell. Ill know more about it once i pull it out from the wall.

Thanks

maybe keeping a regular car charger on it will work. or try a garden tractor battery, there not too awful huge and they hold a decent amount of juice.

Just don't hook it up via the Serial cable it shouldn't have any issues. I remember a few PCA members have done similar things. AT or eGo I believe.

Yea, Part of it is just to get a new battery on it and the other is to get more time out of it too. and since i have a few large forklift batterys i can use it should be able to run the rack for at least a day.

You can run a UPS off ANY battery (or combination of batteries), assuming it's the right voltage. Low wattage UPS units usually run off one 12v battery. Units over 600 watts usually run off 2 or 3 12-volt batteries.

The thing to worry about is charging though.

First of all, most UPS units are designed to charge sealed lead-acid batteries. I would NOT recommend using Nicads, Nickle Hydride, or Lithium Ion, etc, as the charge currents and curves for these are completely different and the battery may explode or catch fire.

Any lead acid battery should take SOME charge, but if you use a battery with a higher current capacity (for instance a car battery or a fork-lift battery) than the original battery it was designed for, it will take a LOT longer for it to charge from the UPS, and it may not fully charge at all.

You could pre-charge the batteries with an industrial charger and then the UPS's charging circuit would probably be enough to keep them trickled until needed. However if they're every deeply discharged you'd need to disconnect them and charge them up again from the heavier duty charger.

Another option is to disable the UPS's internal charger and just rig up your own charger. That charger should NOT be a high-current one though - higher current charging means a higher voltage and that may damage the UPS. You want to rig up a moderate trickle charger.

Thank you. that is how i have been thinking this would work. I wouldent be a problem to have to manualy charge it after an outage. I just wanted to make sure that the UPS cant be dammeged. I know the charging circuit can be but like you said i can add a external charger if need be. Recovery time is not an issue and the unit is activily cooled so im not too worried about burning up the charging circuits.

Again thanks. My boss said he is more then willing to give it a try. He can get anoter UPS (or 4) for the cost of a new battery.

I convert UPS power supplies into 12 volt inverters all the time. The cheap small units just aren't worth buying new batteries for - you can replace the whole unit for almost the same money. Clients give them to me all the time. I cut off the AC wall plug wire, pull the battery, and solder longer wires to the battery cables with alligator clips on them. Most small UPS units will supply 3 - 4 amps from a car battery for hours. Handy in an emergency. I give them away to friends. Keep a couple for myself.

Used one during the last hurricane.

Since their designed to power computers, most UPS units deliver cleaner power than your average power inverter doesn, and inverters aren't cheap.