This paper describes the Nickel-Cadmium Battery Expert System-2, developed under MSFC/ NASA grant NAG8-I05. NICBES is intended to help in evaluation of the performance of the Hubble Telescope spacecraft battery power system. It provides a reasoning system supported by appropriate battery domain knowledge. NICBES-2 is an online, integrated, multitasking diagnostic expert system for nickel-cadmium battery management integrated with a Hubble Space Telescope telemetry data acquisition system. It is currently employed at the Marshall Space Flight Center on a Hubble Space Telescope battery test bed. NICBES diagnoses the performance of the Hubble Space Telescope spacecraft battery power system and alerts personnel to Us possible malfunctions. To achieve this, NICBES provides a reasoning system supported by appropriate battery domain knowledge. The reasoning system is integrated with a telemetry gathering system. The two subsystems cooperate in execution of their tasks and run within a Unix multitasking environment.