The best way to tell if a cell is full? Use a multimeter. There are plenty of cheap quality
devices, and they're not hard to use.
Once you start reading maximum cell voltage (≈4.2V in this case) on the bay, charging has entered the constant voltage (CV) phase. This phase is quite short in brand new high CDR cells like the ones most of you use, and increases in duration as the cell ages due to an increase in the cell's internal resistance. By measuring the duration of your cells CV phase time you can get an idea of its ageing level, as it increases proportionally with the cell's internal resistance. However, since the bay's contact resistances also matter, you would need to promediate a handful of values and make sure your cells are well seated (some twisting can help).
Winblows, love that nick. LoL!
Cheers
