The cordless Dremel Multipro rotary tool uses a rechargeable battery so you work anywhere without having an AC power source. Unfortunately, like most power tools, the battery pack is filled with cheap nickel cadmium cells that don't last very long on a charge and will start to wear out after a couple years. Since the pack uses standard AA size cells, you can replace them with high-capacity nickel metal hydride cells for a battery that lasts 3 times longer.
Step 1: Opening the Pack
The battery pack is held closed by four small plastic tabs on the back. Push them out of the way with a small screwdriver and the blue part will come off.
Now remove the two groups of NiCD cells. They are 700mAh AA's, with little tabs holding them together. Each group is 3.6V, so the tool connect them in either series or parallel to select high or low speed.