A critical review of using the Peukert equation for determining the remaining capacity of lead-acid and lithium-ion batteries

In many applications it is essential to predict the remaining capacity of a battery reliably, accurately and simply. Several existing techniques for predicting the remaining capacity of a lead-acid battery discharged with a variable current are based on variants of Peukertʹs empirical equation, which relates the available capacity to a constant discharge current. This paper presents a critical review of these techniques in the light of experimental tests that were carried out on two lead-acid commercial batteries. The relevance of these Peukertʹs equation based techniques to lithium-ion batteries is also discussed in the light of tests carried on a lithium-ion power battery. The basic conclusion of the paper is that Peukertʹs equation cannot be used to predict the state of charge of a battery accurately unless it is discharged at a constant current and constant temperature.