If you don't already have a good UPS this one is better than most.

they're disposable,when the battery goes Tango Uniform.....you can out and buy another completely new unit. Might as well go cheaper & save yourself some money...buy belkin or enegizer brand

It's "almost" always far cheaper to buy a new battery, unless you thought you had to buy an UPS branded one direct from the UPS manufacturer. Sometimes the UPS manufacturer permanently attaches a proprietary connector to the original battery trying to get you to pay a premium for a new one with same connector built-on <cough>APC,/cough> but in that situation all you have to do is take the harness off the old battery and put it on the new one.

810W UPS probably has something like 2 x 7-8AH batteries in it which cost $15 each. It would surprise me but they might have jumped all the way up in capacity to a $25 battery but even then 2 x 25 < $80.