I have noticed the manual for the HP R5500 XR UPS does not explain all possible solutions when you want to ged rid of the low battery warning light, so here is a quick how to for resolving the issue on your UPS.
- Start off by checking the software for the UPS, or install it if missing (HP Power Manager)
- Consider giving the battery fuse a kick, it`s the fuse placed back up to the right amongst the outlets (Leave it off for 15 seconds++)*
- If you still dont have any luck, replace your battery/batteries.
- If you are using ERM`s, make sure that the UPS knows about them. (Read the manual)
PS: Remember to have redundant power set up, since you might have to give the whole ups a little kick if it`s acting very silly 
* = When turning off the battery fuse, the outlets will still get power from your input power, it just disables the batteries. When turning it on again, the UPS will start a recharge of them.
