Cell Temperature Limiting Fast Charging Method for Lithium-Ion Batteries

Fast charging of high-energy-density lithium-ion batteries is associated with high power losses and results in higher battery temperatures. Heat is the main factor that accelerates degradation mechanisms and can cause thermal runaway. Modified charging strategies, such as the Constant Temperature - Constant Voltage (CT-CV) strategy, rely on a temperature sensor. However, this only provides limited and delayed information about the temperature of the entire battery pack. The temperature is caused by heat generation, and controlling the temperature directly will not necessarily lead to minimum heat generation. By controlling the heat generation, losses can be reduced, and temperature reduction is indirectly achieved. This paper proposes a new approach, called Constant Heat Generation - Constant Voltage (CQ-CV), which aims to maintain a uniform level of heat generation until the end-of-charge voltage is reached and the conventional constant voltage charging is applied. An in-depth analysis of the charging technique, covering its theoretical foundations, experimental setup, and validation through laboratory tests, is presented. The results indicate that implementing the CQ-CV strategy for EV batteries can enhance charging efficiency, and temperature peaks are reduced. This charging strategy can provide new directions for improving the performance and durability of electric vehicle batteries by advancing EV charging technology.

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