A secondary battery including: an electrode assembly including two electrode taps; and a cap assembly including a terminal plate. An N-channel type MOSFET 10 and a JFET 30 of an N-channel type containing a semiconductor material of silicon carbide are individually arranged in proximity on conductive patterns 51, 52 on a substrate 5, and a gate electrode 13 of the MOSFET 10 and a drain electrode 31 of the JFET 30 are connected by a lead 61. A cover is attached to the receptacle and has a number of cavities for receiving the fasteners. The first LED indicator is illuminated when the separable contacts are open. In another feature, a heater is preferably formed with a thick film technology directly onto an insulator element within the motor protector body. The lower case is provided at the front thereof with external input and output terminals.