Calorimetric Study of Ni/H2 Thermal Phenomena

The heat dissipated during various rates of charge, overcharge, and discharge of a nickel-hydrogen (Ni/H₂) cell was measured using a radiative-type calorimeter. A flight configuration-type Ni/H₂ cell was prepared for this study by wrapping the 4-in.-wide cylindrical portion with heater tape and insulating the two dome ends with 10 layers of aluminized Mylar. The radiating surface was limited to the cylindrical portion of the cell. The calorimeter consisted of a liquid-nitrogen-cooled copper chamber arranged inside a vacuum jar. Since the experiments were not performed under isothermal conditions, the term

was included in the equation used to calculate heat dissipation.

Experimentally measured heat values were compared against those calculated using a thermoneutral potential of 1.51 V. Although there was general agreement between the calculated and measured values, a significant difference existed in the instantaneous heat values during charging and the initial stages of cell discharge. The discrepancy is attributed to inaccurate values for the thermoneutral potential and charge efficiency.