APC back up problem

[bigge31566]

I have a APC Back-ups CS500/BK500 and today the electricity blinked a couple of times on and off, but the computer and the back up still worked until about a hour later the back up started alarming and when I looked at it , it was in overload and even when i unplugged everything is still was alarming and also unplugged, removed battery and it stopped but when I reinstalled battery the replace battery light came on, any ideas whats going on

 

[popatim]

It's time to replace the battery. My guess would be it has excessive internal leakage causing a higher then normal current draw when it is charging; hence the overload during the incident.