Runtime, capacity and discharge current relationship for lead acid and lithium batteries

Peukert's equation describes the relationship between battery capacity and discharge current for lead acid batteries. The relationship is known and widely used to this day. This paper re-examines Peukert's equation and investigate its' validity with state of the art lead acid and lithium batteries. Experimental data reveals that for the same battery, Peukert's exponent is not constant but it is a function of battery capacity and discharge current. This work proposes and validates a reformulated equation which provides an accurate prediction of the runtime for single discharge applications using only the battery name plate information such as capacity and the corresponding discharge time. The validation includes lead acid and lithium batteries. Finally, this work introduces and validates a methodology where the battery parameters can be determined in less than one hour when no battery data and usage is available.