In the video below I cover adding a larger battery to an APC Back-ups 350 or 450.
Items You’ll Need
A 12V 9Ah lead acid battery
A Dremel tool with cut off wheel.
The hack takes advantage of the fact that the 350, 450 and 550 APC UPSes use the same enclosure. The 350 and 450 have extra supports molded in to support a smaller battery. We need to remove these supports so the larger battery fits in the compartment.
This is a nice upgrade for those times when you need a little extra run time.