A programmable power system may be used to control the supply of power from a battery to protect the battery from accidental discharge and excessive wear. A programmable power control unit may be connected between a battery and one or more battery operated devices. Typically, the battery is installed in a vehicle (e.g., a motor vehicle, an airplane, or a watercraft) although the unit may be used with any battery powered system. The programmable power control unit may be used to control the supply of power from the battery to one or more auxiliary devices, such as, for example, a two-way CB and ham radio, an AM/FM radio, a music player, a PDA, a TV, a DVD player, a cellular phone, a radar device, a GPS device, a data terminal, a display, and a computer. The programmable power control unit automatically turns the devices on in response to a predetermined battery operating condition, and turns the devices off after a predetermined time period in response a non operating condition.