I would second the above. I know for a fact that you can replace the battery with a regular car battery and they work fine and can increase life by 4-5 times or more of the UPS. I have done so myself. You and also stack multiple batteries together and increase the lifespan further. Just keep in mind there is a gas given off by car batteries when they charge / are heavily used. This mod is best performed for use where there is good ventilation.



Also, check the body on them. I have found a lot of aluminum in them. I average about $2.50-$5 each out of them depending on size, age and current prices.

Something to keep in mind is if it is only the batter that is shot, most will still work as a surge protector / power strip anyways. They just wont keep the plugged in items on in the event of power failure.