If everything was off (no power usage) during that time then yes the battery could be due for replacement. Charging it overnight was a smart thing to do
I posted some info about KiB monitor panel lights here: http://www.classbforum.com/forums/f5...ghts-2295.html
You could confirm that it needs replacing by applying a small load for a short time. If the voltage, as indicated by the lights, drops off dramatically and doesn't recover after the load is removed that would indicate it's time to replace the battery(ies).
Here are my load test results (two tests) on a two battery or two battery equivalent system: http://www.classbforum.com/forums/f8...html#post27559
A nearly 6 amp load for an hour had minimal impact on the system capacity/voltage. That confirmed my batteries were good.