This document provides an overview of nuclear power batteries, which utilize radioactive decay to generate electricity. It discusses two main categories of nuclear batteries: 1) Thermal converters, which convert heat energy to electrical energy, including thermionic converters, radioisotope thermoelectric generators, thermophotovoltaic cells, and alkali-metal thermal to electric converters. 2) Non-thermal converters, which extract energy directly as radioactive isotopes decay and do not rely on temperature differences, such as direct charging generators. The document outlines the basic scientific principles and potential applications of various nuclear battery technologies for long-term, remote, or high-power uses where other battery types are impractical.