Failure Model for a Leaking Nickel-Hydrogen Cell
AEROSPACE CORP EL SEGUNDO CA LAB OPERATIONS
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A model has been developed and used to analyze the loss of capacity and dry out of nickel-hydrogen cells as a result of pressure vessel leaks. This analysis has allowed a number of conclusions to be drawn about the behavior of nickel-hydrogen cells with leaks Cells that are repeatedly cycled may not lose all capacity by leaking their hydrogen. There is a leak size threshold at 1-2.5 um below which nickel-hydrogen cells will not dry out by gas. There is a leak size threshold at 0.1-0.2 um below which it will be difficult to identify the rate of capacity loss as differing significantly from normal wear-related capacity loss rates. Pre-existing leaks smaller than about 0.1 um cannot be detected by typical leak detection methods. Leak latency can occur if pre-existing subthreshold leaks grow in size during the cell operation.
- Electrochemical Energy Storage