On the efficacy of SoC-preconditioning on the utilization of battery packs in Electric Vehicles

Abstract

During the last decade Electric Vehicles (EVs) surged in popularity. However, their mass adoption is slowed by the limited capacity of their Energy Storage System (ESS). Lithium Ion (Li-Ion) technology has established itself as the de-facto standard for mobile applications, though its energy density and cost put a hard limit on the maximum size of viable EV battery packs. Maximizing its utilization therefore becomes of central importance. To efficiently use a battery pack over its entire lifetime, the State of Health (SoH) of the cells needs to be taken into account. In this paper, we propose a novel preconditioning algorithm to minimize the time an EV is connected to the charging station. Our proposed approach uses existing Active Cell Balancing (ACB) hardware of the battery pack to precondition the State of Charge (SoC) of cells such that all cells reach the top SoC threshold at the same time without requiring an additional balancing phase during charging. This is done by considering the individual cells’ SoH to precondition them for achieving an equal time to charge fully. Applying the same approach for discharging, we can extend the driving range of an EV, which otherwise is limited by the cell with the lowest SoC in the pack. Our analysis of various usage scenarios shows that our proposed preconditioning algorithm increases the usable energy of the battery pack by up to 1.8% compared to conventional balancing algorithms while effectively halving the time connected to a charging station, all without requiring any additional hardware components.