PERFORMANCE OF VALVE-REGULATED LEAD-ACID BATTERIES UNDER SIMULATED ELECTRIC-VEHICLE DUTY.

December 2002

Electric Applications Inc. (EAI) staff have been developing infrastructure for the operation of electric vehicles (EVs) for over 10 years, including both hardware and operating strategies. In this project, they developed operating strategies for EVs supplied by the Frazer Nash Company. The vehicles were fitted with VRLA batteries and charged with low-power, on-board chargers. EAI staff were employed to determine the expected cycle life of two AGM batteries (designated AGM1 and AGM2) when operated in these EVs. EAI staff developed a simulated discharge profile based on data obtained during operation of a Frazer Nash vehicle around downtown Phoenix. Three overall operating schedules have been formulated by combining this discharge profile with either of three different charging procedures. The first overall operating schedule, termed operating-schedule 1, completes the charging procedure with a constant current. The second schedule, called operating-schedule 2, finishes charging with a dI/dt control. An overall operating strategy has also been developed specifically for the AGM2 batteries (12-V; 67 Ah). Two AGM1 batteries cycled according to operating-schedule 1 performed only 60 cycles before failure, whereas two operated under operating-schedule 2 delivered 70 and 153 cycles before failure. The batteries also experienced a very high self-discharge rate. Based on the poor cyclic performance and the unfavorable self-discharge data this technology, in its current state of development, is not considered sufficiently robust for use in the Frazer Nash EVs.Two AGM2 batteries provided 215 and 220 cycles before their capacity decreased to 50% of the nominal value. As a result of this poor performance, they are not recommended for use in the Frazer Nash vehicles.

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