(Invited) Internal Gas Pressure Measurement of Packaged Electric Double Layer Capacitors

Abstract

One mode of electric double layer capacitor failure is package rupture, which usually leads to rapid deterioration of its electrical performance. This typically is caused by gas generated within a sealed capacitor with a subsequent pressure rise that eventually leads to the package bursting. The rate of gas generation, which ultimately can determine capacitor life, depends on materials purity, capacitor operating voltage, and the capacitor operating temperature. We measured the internal gas pressure and rate of gas pressure rise in spiral-wound, packaged electric double layer capacitors using an indirect and a direct approach. The indirect approach relied on physically measuring capacitor package deformation that had been caused by the internal gas pressure. This was then quantified by comparing the value with deformation caused by a known applied gas pressure. The direct approach relied on the use of an attached and calibrated solid-state pressure transducer. Internal gas pressure measurements using both approaches were made on 100-F-size electric double layer capacitors held at several temperatures with different applied voltages. Experimental details are reported with internal pressure measurements shown for 2000 hours of capacitor aging at 65 oC. Figure 1