Influence of cycling current and power profiles on the cycle life of lead/acid batteries

Abstract

Batteries are assembled with positive plates of the novel strap grid tubular (SGTP) design described in a previous paper [1]. These batteries are subjected to four tests: (i) Peukert dependence determinations; (ii) classical galvanostatic cycling (5 h charge and 1 h discharge); (iii) EV-SFUDS, and (iv) EV-ECE-15 cycling tests. It has been established that the Peukert dependence curve of SGTP batteries is very close in profile to that for SLI batteries. This guarantees SGTP's batteries high power performance. These batteries endure over 950 cycles on galvanostatic cycling. When cycled according to the SFUDS power profile under a current load of 320 A/kg positive active mass during the 15th SFUDS step, SGTP batteries exhibit a cycle life of 350–450 cycles. If the current density during the 15th step is 190 A/kg PAM, the batteries endure over 600 charge/discharge cycles. The life of positive SGT plates is limited by power loss, but not by capacity. Similar results have also been obtained from ECE-15 cycle-life tests. On cycling SGTP batteries with a current load of 210 A/kg PAM during the 23rd ECE-15 step (the step during which maximum power output is demanded from the battery), they endure between 550 and 650 charge/discharge cycles. A summary of the test results obtained for two batches of experimental batteries indicates that there is a direct dependence between the SGTP battery cycle life and the maximum current density on discharge. Increasing the discharge current density decreases the battery life. It has also been established that the capacity on SFUDS (ECE-15) discharge declines gradually on cycling in favour of the residual galvanostatic capacity at 5 h rate of discharge (100% depth-of-discharge) which increases. This implies that two types of structures are formed in the positive plates on cycling: the first type ensuring high power output and the second type yielding low power but long cycle life. The higher the power delivered by the positive plate, the faster the conversion of the structure supporting this high power output into such yielding low power performance. EV-SFUDS: A simplified version of the Federal urban driving schedule for electric vehicle battery testing, US Department of Energy, USA, 1988, and ECE-15: a standard European test cycle, speed versus time.