Optimal pulse-modulated Lithium-ion battery charging: Algorithms and simulation Huazhen Fang a, *, Christopher Depcik a , Vadim Lvovich b a Department of Mechanical Engineering, University of Kansas, Lawrence, KS 66045, USA b NASA John H. Glenn Research Center, Cleveland, OH 44135, USA A R T I C L E I N F O Article history: Received 29 July 2017 Received in revised form 7 November 2017 Accepted 8 November 2017 Available online 7 February 2018 Keywords: Pulse charging Charging management Battery management Fast charging Control theory A B S T R A C T This paper focuses on the development of optimized pulse charging strategies for Lithium-ion (Li-ion) batteries. Aiming to improve the constant pulse charging in wide use today, we propose for the first time to modulate the current pulses during the charging process to reconcile health protection with charging pace. Toward this end, we use an equivalent circuit model and then formulate the problem of optimal pulse charging with an awareness of both battery health and charging speed. We then propose to resolve it using the linear control theory and obtain two charging methods, which regulate the magnitude and width, respectively, of the current pulses applied during the charging process. The proposed methods promise a two-fold benefit. First, the pulse-modulated charging will offer an effective means to defend the battery against the charging-induced harm to health without much compromise of the charging speed. Second, the methods have low computational cost, thus suitable for embedded battery management systems (BMSs) with constrained computing capabilities. This compares with the many charging techniques in the literature that require time-consuming constrained optimization. A detailed simulation study of the two proposed methods is offered to evaluate their effectiveness. The study endows pulse charging with a formalized design methodology unavailable before and impose a stronger health protection during its execution, which together can potentially translate into the momentum for its real-world application to Li-ion battery-powered systems including consumer electronics devices, electrical vehicles and solar photovoltaic arrays. © 2017 Published by Elsevier Ltd. 1. Introduction Recent decades have seen a rapidly growing use of Lithium-ion (Li-ion) batteries, which have seen wide penetration in grid, renewable energy facilities and energy-efficient buildings. In these applications, battery management systems (BMSs) play the essential role of monitoring and regulating the operational status of the Li-ion batteries for improved performance, life, and safety [1,2]. A wealth of research of advanced BMS algorithms has thus come in response to this need. Prior, the focus was mainly on the state-of-charge (SoC) and state-of-health (SoH) estimation, aging status monitoring and thermal monitoring [2]. However, what has been less researched is the charging management, despite the consensus that improper charging protocol can cause fast capacity fade and a shortened life due to the fast build-up of internal stress and resistance, crystallization, and other negative effects [1,3–7]. Literature review.Charging by a constant current or a constant voltage is a popular industrial practice [8]. Yet, its relatively easy implementation comes at the expense of decrease in the battery cycle life. An improved approach is the constant-current/ constant-voltage (CC/CV) charging [2,8]. Initially, a trickle charge (0.1 C or even smaller) is used for depleted cells, which produces a rise of the voltage. Then, a constant current (often between 0.2 C and 1 C) is applied. This stage ends when the voltage rises to a pre-specified level. It then switches to the constant voltage charging mode. The current diminishes in this mode, but the SoC continues to grow. In recent years, pulse charging has gained much interest among practitioners as an alternative beyond CC/CV. Its current profile is composed of pulses over time. Between two consecutive pulses is a short rest period, which allows the electrochemical reactions to stabilize by equalizing throughout the bulk of the electrode before the next charging pulse begins. This brief relaxation can bring multiple benefits to a Li-ion battery, including better charge acceptance, reduced gas reaction, inhibited dendrite growth, slowed capacity fade and faster charging rates [9–12]. * Corresponding author. E-mail address: fang@ku.edu (H. Fang). https://doi.org/10.1016/j.est.2017.11.007 2352-152X/© 2017 Published by Elsevier Ltd. Journal of Energy Storage 15 (2018) 359–367 Contents lists available at ScienceDirect Journal of Energy Storage journa l home page : www.e lsevier.com/loca te/est