Replace two alkaline AA cells in your gadgets with one LiFePO4 cell and one of these dummy cells. The ends are connected together with a short piece of 4-mm nickel strip put in place during the print. I have a label printer that takes six, and it didn't like it when I tried running it on NiMH rechargeables (only 7.2V output vs. 9.0V for alkaline). 9.6V from three LiFePO4 cells will be a little bit high, but shouldn't be dangerously so.