There is a new circuit there that lets you pick from 1-3 cells as well as the current to charge at.

[link]http://www.shdesigns.org/pdf/lionchg3.pdf[/link]

You can build this charger for a 3 cell pack but If you are going to use both 2 and 3 cell packs then I would not use this charger. I would spend the extra money and get an automatic one, one tht sense the voltage in the pack and wont let you charge a 2 cell on a 3 cell setting. This is when the fires happen, it just not worth the risk.

Matt