Thermal effects in VRLA cells and comparison with wet lead-acid cells under different operating conditions

Sealed valve-regulated lead acid cells (VRLA) of the absorbent glass mat type suffer adversely from thermal effects compared to wet lead acid cells. Data are presented to show heat distribution in a battery stack of horizontally packed 500 Ah VRLA cells. Float and shallow cycling are examined since each have their own contribution to heat distribution. Comparison with equivalently sized wet cells is shown in the shallow cycling mode, which simulates peak-shaving. The data show the current and voltage limits during float charge to be significant factors in proper thermal management to avoid runaway. In a shallow, continuous peak shaving type cycling at constant power, considerable heat generation is observed for the VRLA cells. A new jar design with integral vertical ribs, coupled with a perforated steel housing, helps to significantly reduce the heat build up, as well as the temperature differential