Determining Lithium-ion Battery One-way Energy Efficiencies: Influence of C-rate and Coulombic Losses

This paper addresses the lithium-ion battery efficiencies, a fundamental characteristic normally not given in battery specification sheets and often overlooked in research papers that consider battery application and modelling. In-house experiments were performed to obtain: (i) charging/discharging curves with different C-rates and (ii) open-circuit voltage characteristic. The results were used to analyze battery coulombic and energy efficiencies, which lead to methodology for accurately assessing one-way energy efficiencies. Utilization of accurate one-way efficiencies potentially improves a variety of battery models and algorithms for state-of-charge estimation. In addition, residual capacities (after discharging with higher C-rates) are measured and their influence on roundtrip efficiencies is assessed.