A Comparison of Internal and External Preheat Methods for NMC Batteries

Abstract

Lithium-ion batteries (LiBs) performance can be significantly declined when operated at cold climates in terms of capacity loss, resistance increase and accelerated aging rates. To prevent this downgrade and to maintain the optimal operation of battery cells, a preheat process is taking place, which can be implemented either by internal or external techniques. The former is performed actively, by circulating a constant amplitude and frequency alternative pulse current (APC) at the battery cell’s terminal and preheating it internally by harvesting its generated Joule losses. The latter is achieved passively, by enclosing the cell into thermal blankets. In this work, a comparison of these two preheating strategies is presented, by proposing electro-thermal and lifetime models of a lithium nickel manganese cobalt oxide (NMC/G) 20 Ah pouch battery cell. Heat transfer, energy efficiencies and degradation costs are estimated during operation of the preheat techniques. Validation of the model showed a good agreement between the model and experimental data, and a study case is proposed to estimate and compare the cost efficiency of the methods as based for an economic study.