You can find thermal energy everywhere in the world, including geothermal energy. Here we report an amazing battery that could supply power semi-permanently by simply burying the cell in a heat source and turning the switch on and off. We examined the discharge termination process of a sensitized thermal cell (STC), a new thermal energy conversion system for generating electrical power from heat previously reported by the authors. To observe this termination process, we constructed a new STC system using a narrow-bandgap semiconductor, germanium (Ge), and surprisingly found that the battery characteristics were restored after discharging by placing or burying the battery in a heat source. This discovery should bring us closer to solving global energy problems.