INFLUENCE OF CYCLING CURRENT AND POWER PROFILES ON THE CYCLE LIFE OF LEAD ACID BATTERIES/

Batteries are assembled with positive plates of the novel strap grid t ubular (SGTP) design described in a previous paper [1]. These batterie s 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 establish ed that the Peukert dependence curve of SGTP batteries is very close i n profile to that for SLI batteries. This guarantees SGTP's batteries high power performance. These batteries endure over 950 cycles on galv anostatic cycling. When cycled according to the SFUDS power profile un der a current load of 320 A/kg positive active mass during the 15th SF UDS step, SGTP batteries exhibit a cycle life of 350-450 cycles. If th e current density during the 15th step is 190 A/kg PAM, the batteries endure over 600 charge/discharge cycles. The life of positive SGT plat es is limited by power loss, but not by capacity. Similar results have also been obtained from ECE-15 cycle-life tests. On cycling SGTP batt eries 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 batte ry), they endure between 550 and 650 charge/discharge cycles. A summar y of the test results obtained for two batches of experimental batteri es indicates that there is a direct dependence between the SGTP batter y 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 decline s gradually on cycling in favour of the residual galvanostatic capacit y at 5 h rate of discharge (100% depth-of-discharge) which increases. This implies that two types of structures are formed in the positive p lates on cycling: the first type ensuring high power output and the se cond type yielding low power but long cycle life. The higher the power delivered by the positive plate, the faster the conversion of the str ucture supporting this high power output into such yielding low power performance. EV-SFUDS: A simplified version of the Federal urban drivi ng schedule for electric vehicle battery testing, US Department of Ene rgy, USA, 1988, and ECE-15: a standard European test cycle, speed vers us time.