Why cant I use a 9.6V battery in a 12V Drill?
The tools are designed to run at the specific voltage provided by the battery pack. Too much voltage, as well as too little voltage, can cause poor performance and life from the tool. The tool may run for short periods of time with the wrong battery pack, but it shortens the overall life of the product. This is the same reason corded products designed for 220V cannot be used in the U.S. where we have 120V outlets.
