A High-Efficiency Capacitor-Based Battery Equalizer for Electric Vehicles

Technology in electric vehicles has increased substantially in the past decade. Moreover, it is projected to grow at record highs in the coming years since these vehicles are needed to reduce the contamination related to the transportation sector. One of the essential elements of an electric car is its battery, due to its cost. Batteries comprise parallel and series-connected cell arrangements to meet the power system requirements. Therefore, they require a cell equalizer circuit to preserve their safety and correct operation. These circuits keep a specific variable of all cells, such as the voltage, within a particular range. Within cell equalizers, capacitor-based ones are very common as they have many desirable characteristics of the ideal equalizer. In this work, an equalizer based on the switched-capacitor is proposed. A switch is added to this technology that allows the disconnection of the capacitor from the circuit. In this way, an equalization process can be achieved without excess transfers. Therefore, a more efficient and faster process can be completed. In addition, it allows another equalization variable to be used, such as the state of charge. This paper studies the operation, power design, and controller design of the converter. Moreover, the proposed equalizer was compared to other capacitor-based architectures. Finally, simulation results were presented to validate the theoretical analysis.

Automated summary

Technology in electric vehicles has significantly improved in the past decade and is expected to continue growing rapidly in the coming years to address the issue of transportation-related pollution. The battery is a crucial component of electric cars due to its high cost. Cell equalizer circuits are essential to ensure the safety and proper functioning of batteries, by keeping all cells within a specific range of variables such as voltage. This research proposes a switched-capacitor-based equalizer that allows for more efficient and faster equalization processes, as well as the use of additional equalization variables. The paper examines the operation, power design, and controller design of the converter, compares the proposed equalizer with other capacitor-based architectures, and presents simulation results to validate the theoretical analysis.