Boundaries of high-power charging for long-range battery electric car from the heat generation perspective

Abstract

High-power charging (HPC) has been associated with a great potential to shorten the charging time, relative to increasing the all-electric range (AER) of battery electric cars (BECs). Such promise of applicability is however restrained by setbacks attributed to the high-voltage system of BECs, its negative influence on the battery performance, and a higher requirement of charging infrastructures. More importantly, the core issue is the functionality of the battery, as research has found that HPC may cause a high charging rate on the battery cell that consequently promotes its heat generation and eventually results in a significant loss of functionality and safety degradation. Considering these elements, the thermal reaction of a battery under HPC is seemingly the key toward the design of an effective thermal management system. Thus, we conducted the present study with a focal objective of examining the thermal reaction of a traction battery to the HPC, to evaluate the gap between existing battery technologies and HPC to find the suitable condition. We investigated the heat generation characteristics of Nickel–Cobalt–Manganese (NCM) and lithium iron phosphate (LFP) batteries by HPC testing in non-adiabatic and adiabatic conditions, respectively, for different charging rates from 0.5 to 5.0C. We analyzed and incorporated the test results to establish a model of battery heat generation, which could predict temperature rise under specified conditions. Moreover, we proposed an HPC operating boundary by considering the present battery technologies. The findings herein indicate that the increased charging rate leading to higher heat generation and lower charge efficiency can be effectively handled through specific thermal management, which, with the boundary, provides a limit for the optimal operation region to avoid safety risk. More practically, a good thermal management system is required to control the boundary setting and extend the operation region of battery charging.