Hi, After some research, I have found that Li-ion cells can be very dangerous if charged to a too high voltage, also if allowed to go below a certain voltage. There are some cells with over/under voltage protection and some without, I'm not sure how well these protection circuits work. I want to build a SAFE circuit, that: 1/ Works with a low input voltage, 5-12V. 2/ That will guarantee that each cell doesn't go over this voltage. 3/ Possibly keeps 'say' 4-6 cells in one pack and can used together, with hopefully low voltage protection. Cheers, Camerart.