Hi Paul! Like Polygot said I read the document at the Energizer website they do recommend to charge cell by cell individually rather than charge them in series. The charger does several things to monitor the amount of charge. It checks to see if the voltage started to fall then it's full and also if the temperature raise rapidly then it's full. They do say that if you do not have the ability to monitor the charge like these smart charger then charge them at 10 hr rate so that there is less chance of over charging them. I wonder the sub C cells that you're getting what's the mA rating on them? I have found a lot of C and sub C NiMH cells that the capacity is about the same as AA cells although they are much bigger.