Fast Charging of Lithium-Ion Batteries using Constant Temperature Constant Voltage (CT-CV) Method for Electric Vehicles Application

Abstract

Electrification of transport is one of the considered plans to address environmental concerns. However, wide-scale adoption of Electric Vehicles (EVs) has remained limited due to various challenges such as longer charging time, limited driving range, battery charging and discharging cycles, and an inadequate charging infrastructure. Lithium-Ion batteries are mostly used in EVs, which have higher energy density, and are eco-friendly. A body of researcher is focused on reducing charging time and improving life span of lithium-ion batteries through developing effective control techniques such as open loop and control loop methods. Closed loop charging method reduces the charging time of the battery as compared to open loop method. Existing constant temperature-constant voltage (CT-CV) technique needs to improve its control circuitry and design. This research work is focused on design and implementation of CT-CV technique by employing a feed-back proportional-integral (PI) controller with rectifier boost converter, considering temperature as a key degradation metric, for fast charging of EVs. Voltage Mode (VMC) and Current Mode Control (CMC) methods have also been implemented to maintain the battery voltage, current and temperature at safe operating limits i.e., 35 to 45. Simulations are performed in Simulink and experiments are carried out to validate the obtained results. As per results, more than 30% faster charging is attained through the both VMC and CMC technique by employing CT-CV technique using PI controller. Experimental results reveal that the proposed technique charges up to 20% faster than that of the reference battery. In addition, improved power factor close to unity is achieved, as rectifier current and voltage waveforms are sinusoidal, which increases the efficiency of the li-ion battery.