Pulse Power Nickel Metal Hydride Battery 2002-01-3246
EEI bipolar nickel metal hydride batteries and cells were tested under various conditions relevant to consumer and aerospace pulse power applications, with differing power and discharge pulse time requirements. A generic hybrid vehicle specification required that a full scale battery obtain 300,000 life cycles, while being able to deliver 25 kW discharge power after 18 seconds and 30 kW recharge power after 2 seconds. This corresponds to 15 years of normal use. Using this testing procedure, over 300,000 life cycles were obtained (using 25 Wh energy swings, scaled) on single full-capacity cells, with less than 10-15% pulse power capability loss measured. The projected full-sized battery mass was 40 kg and volume was 20 L. Testing of selected cells is continuing. Another test related to an automotive application demonstrated that a 6 Ah cell starting at 50% SOC was capable of being discharged at 200 A for 10 seconds (33C), with an end voltage of 0.945 V. An application involving the use of 1 second discharge pulses demonstrated power densities of about 3 kW / kg and 8.6 kW / L at the single cell and small battery (6 V) levels. About 120,000 cycles were obtained under these conditions. These test cells used thinner electrodes than those related to automotive applications. Based on these data, several alternative pulse power designs are presented.