If you have many rechargeable 123 form factor cells, the Ultrafire charger is great. It allows 3.0 or 3.6V cells to be charged and charges 2 of them at once. The unit is fairly small and comes with a nice and long power cord. You first select what voltage cells you are charging, then put in one of two cells and it charges them both at the same time. It costs more than a Nano charger but worth it for the dual voltages and dual cell charging.