Pseudo bipolar nickel-cadmium batteries used as filter elements to pulsed current loads

This investigation consisted of several tests of specially fabricated nickel-cadmium batteries having circular disk type electordes. These batteries were evaluated as filter elements between a constant current power supply and a 5-hertz pulsed load demanding approximately twice the power supply current during the load on portion of the cycle. Short tests lasting 10,000 cycles were conducted at up to a 21 C rate and an equivalent energy density of over 40 Joules per pound. In addition, two batteries were subjected to 10,000,000 charge/discharge cycles, one at 6.5 C rate and the other at a 13 C rate. Assuming an electrode to battery weight ratio of 0.5, these tests represent an energy density of about 7 and 14 joules per pound respectively. Energy density, efficiency, capacitance, average voltage, and available capacity were tracked during these tests. After 10,000,000 cycles, capacity degradation was negligible for one battery and about 20% for another. Cadmium electrode failure may be the lifetime limiting factor extremely low depth of discharge cycling. The output was examined, and a simple equivalent circuit is proposed.