A battery includes a first terminal, a second terminal, an outer layer, and a power indicator apparatus. The power indicator apparatus comprises an electrical conductor and a mechanical switch. The electrical conductor is configured to be in continuous electrical communication with the first terminal. The mechanical switch is configured to be actuated by an application of pressure at a single location, and upon actuation, to place the electrical conductor in electrical communication with the second terminal such that the power indication apparatus can facilitate a reading of a potential energy stored in the battery. Methods of determining a potential energy stored in the battery are also provided herein.