Evaluation of Fast Charging Efficiency under Extreme Environmental Conditions in Brazil

Abstract

<div class="section abstract"><div class="htmlview paragraph">Fast chargers are necessary for the success of vehicle electrification. These devices can achieve a battery charge rate greater than 4C, significantly increasing the amount of heat generated by the battery. Additionally, the operating temperature of the storage device directly influences the device’s efficiency and lifespan. Given the importance of operation temperature, the Battery Management System (BMS) plays a key role in mitigating heat generation and degradation effects. Despite BMS optimizing battery operation under all possible conditions, the use of fast chargers in extremely hot and cold environments still lowers overall efficiency. In these two worst-case scenarios, the thermal system must manage the ideal charging temperature by consuming part of the energy supplied by the charger. The present work aims to evaluate the charging energy efficiency and time with fast charger utilization, considering the Brazil’s minimum and maximum temperatures registered in 2020. In order to establish the same comparison basis, a vehicle with battery capacity of 42 kWh is modeled and a simplified BMS charging strategy is defined. Experimental tests are done for an electric vehicle submitted to fast charging to validate the model. The results point out that charging under the extreme hot temperature is more efficient than the extreme cold temperature. In comparison to charging at 30°C, charging under the extreme hot temperature decreases the overall efficiency by 1.32% and raises the total charge time by 97 seconds. For the colder temperature case, the efficiency reduction obtained is 4.36% and the time increase by 10 minutes.</div></div>