I have had an APC 500 UPS for years. The battery started giving
warnings that it needed replaced. I didn't listen right away and
eventually the old battery caused problems. I ended up loosing two
PSU's and having flaky results on my WIFI AP until I realized the
problem was the UPS. So I removed the UPS.

I replaced the APC 500 UPS battery with a battery direct from APC. I
let it charge for a day before putting it back in. It is now back in
place and running. The APC software asked me if I replaced the battery
and I selected that I had.

Now the battery is going from 100% charged down. Right now it is at
78% and dropping slowly. Is this normal calibration? I can't find
anything about this on the web. I am worried that this is not normal
and there are additional problems with the UPS.