AZ Technology and SRI Develop Battery System

April 06, 2003 by Jeff Shepard

AZ Technology Inc. (Huntsville, AL) and Symmetry Resources Inc. (Arab, AL) have developed and qualified a 270V flight battery system for NASA’s X-38/Crew Return Vehicle (CRV) to the International Space Station. It is claimed to be the first 270V battery system approved for human spacecraft.

The battery system powers flight-control surfaces’ electromechanical actuators and parafoil winches; utilizes a self-contained ground support equipment unit to provide fast charge/discharge control and battery diagnostic functions using 120Vac input; performs battery diagnostics and provides battery status information such as temperature, effective internal resistance, voltage and capacity; provides analog outputs and digital input/output via an RS 232 port; and has safety interlocks that enable dead-face cable connections.

The 270V battery utilizes commercially available, sealed nickel-cadmium cells and has a rated capacity of 9.6Ah. The battery consists of four 210-cell strings with individual control electronics and protection circuits. The cell string design is capable of delivering up to 2,870W/L or 1,120W/kg, in a pulsed, duty cycle application. The battery easily delivers the required 36kW to 100kW millisecond pulses over a 220-second duration at 50-percent state of charge.