Replacing the battery is going to be much cheaper. I'd be surprised if any UPS doesn't have a replacable battery. it's very easy generally, unscrew the bottom (check for hidden screws under rubber pads and stickers), find the battery and search the number printed on it. find one you like, double check that the voltage and Amp hours/Watt hours is very close, order, connectors should come off easy. I suggest Enersys for a battery replacement brand, I've used them for years and they have good life but they are slightly more expensive.