A Critical Review of Using the Peukert Equation and its Generalizations for Lithium-Ion Cells

Abstract

In this paper, the Peukert’s equation was studied experimentally and theoretically at various discharge currents for lithium-ion cells. The classical Peukert’s equation is not applicable at small discharge currents as according to this equation, at the discharge current decrease, the capacity released by the cells tends to infinity. The generalized Peukert’s equation C = Cm/(1+(i/i0)n) corresponds well to the experimental data obtained at small and middle discharge currents. However at high discharge currents, the capacity released by the lithium-ion cells drops much faster than it is predicted by the known Peukert’s equation generalizations. In this paper both experimentally and theoretically, it is proved that the reason of the sharp decrease of the cells capacity at high discharge currents is the voltage drop at cells internal resistance. Based on the obtained results, the following equation was proposed: C = Cm(1−i/i1)/((1−i/i1)+in/i0n). This equation corresponds well to the experimental data at any discharge currents, as it takes into consideration the voltage drop, caused by the cell internal resistance.