Thermal batteries are known by different names: molten salt batteries, or liquid sodium batteries. All these refer to the fact that the electrolyte is a mixture of solid sodium or lithium salt that becomes liquid when heated. The batteries are designed for a specific application so that the electrical characteristics, activation time, environmental conditions, and mounting conditions are satisfied. This type of battery is useful in applications that need a long shelf life with no maintenance, high power density, or a ruggedization.  It has shown to be useful in guided weapon systems and is gaining popularity in electric vehicles. This technology has been successfully utilized in ground vehicles, launch vehicles, marine applications, oil and gas drilling and satellites. Figure 1 shows some examples of the applications where thermal batteries work reliably. When used, thermal batteries can provide several output voltages from one battery and are compatible with either steady load conditions or pulsed applications. Their versatility permits them to replace several power sources due to their reduced size, weight and improved reliability.