A lithium-polymer based battery pack for power a hand held power tool or a garden tool, the battery pack has a plurality of battery cells located within housing that is selectively connectable to and supportable by a hand held power tool or a garden tool. The battery cells have a lithium-polymer based chemistry and a nominal charged internal impedance of less than or equal to approximately 5 milliohms. In one embodiment the cells are think cells are stacked within the housing such that each sell is layered over or under an adjacent cell and a resiliently deformable substrate located between adjacent battery cells. In another embodiment the cells may be interconnected to have a combined output voltage of at least 9 volts and to produce a combined average discharge current of greater than 20 amps. A lithium-polymer tool battery and a battery powered tool are also part of the invention.