Gas evolution and performance assessment of submarine lead/acid batteries

The gas-evolution rates from new and end-of-life lead/acid submarine cells at both open-circuit and under float-charge have been examined, together with the discharge performance of the cells. The evolved gas is found to comprise hydrogen and oxygen only. The open-circuit and float-charge hydrogen-evolution rates vary logarithmically with temperature. The enthalpy of activation for open-circuit hydrogen evolution is 70 kJ mol−1 for both old and new cells. The open-circuit hydrogen-evolution rate per Ah of rated capacity for new cells is between 0.00636 and 0.105 cm3 h−1 Ah−1 at STP at 20–50 °C, respectively. For old cells, a> three-fold increase is observed; the evolution rate ranges from 0.0237 to 0.361 cm3 h−1 Ah−1 at STP at 20–50 °C, respectively. On float-charge, using an uncompensated float voltage, the hydrogen-evolution rate of new cells is between 0.0166 and 0.241 cm3 h−1 Ah−1 at STP at 20–50 °C, respectively. For old cells, the rates increase to 0.0298–0.903 cm3 h−1 Ah−1 at STP at 20–50 °C, respectively. In contrast, the electrical discharge performance of the cells decreases with age. This suggests that the active area for hydrogen evolution increases with age, but that the active area for electrical discharge decreases. No correlation has been established between hydrogen evolution in individual cells and electrical discharge performance for cells of the same age. The self-discharge rates of the negative plates at 20 °C are 14 and 50% per year for new and old cells, respectively.