Thermal Analysis of Lead‐Acid Cells for Load‐Leveling Applications

Abstract

Modeling studies have been conducted to determine the temperature field in a lead‐acid cell contemplated for load‐leveling applications, with daily duty cycles and a weakly equalization charge. The results show that under the proposed daily cycling and without a forced cooling, a maximum temperature rise of 16°C can be expected at the center of a proposed 9.76 kW‐hr cell . For such tall lead‐acid cells, reduction of cell length by about one‐half would reduce the temperature rise by 7°–8°C without employing forced cooling. Conventional water cooling at the cell terminals has little effect in lowering the cell maximum temperature. Moreover, cooling may induce a large temperature gradient in the vertical direction of the cell, which may cause a nonuniform current distribution over the electrode leading to a gradual loss of cell capacity and cycle life. Practical cells in use often incorporate "air lift pump" that facilitates electrolyte stirring or an electrolyte circulation design to minimize the extreme temperature gradients. Gassing during the weekly equalization charge of loading‐leveling cells may also enhance internal heat transfer, causing a more uniform temperature distribution. After the weekly equalization charge, the cell temperatures resume their initial values at the end of the rest period.