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The determination of the hydrogen pressure equivalent to one amp hour of stored capacity has been conducted at various rates of charge and discharge and at different temperatures. Cell temperature control in this determination contrasts isothermal versus cold plate conditions. Selected regions of the hydrogen pressure plots are evaluated in terms of consistent cell pressure factors. Pressure factors determined on charge suggest a maximum coulombic efficiency of 96% to that obtained on discharge.

Hydrogen gas pressure has been utilized to determine state of charge, efficiency on charge, establish voltage/current relationships and to derive an equivalent cell level DC resistance. In response to a fixed measurement cycle, the studied cell design is able to store more charge at lower temperatures. This is accomplished by more efficient charging to a higher cell voltage. However, as higher states of charge (pressure) are attained, the discharge profile depresses. This corresponds to an increased cell DC resistance. Furthermore, this cell level DC resistance increases with the depth of discharge and the rate of this increase is greater at lower temperatures.