Intro: Electric mobility is transforming transportation, with EV charging systems and lithium-ion batteries taking center stage. As the lifeline of electric vehicles, lithium-ion batteries significantly influence performance and efficiency. Understanding their charge-discharge curve and other technical aspects is essential for optimizing their use and longevity.
Charging Lithium-Ion Battery Packs: Lithium-ion battery packs, formed by combining individual cells, rely on the constant current and constant voltage (CC-CV) charging method to maintain efficiency and safety.
The CC-CV process begins with constant current charging, during which the battery pack’s voltage steadily increases. Once the battery reaches its full charge cut-off voltage, the constant voltage mode takes over. During this phase, the charging current gradually decreases until it drops below 0.05C.
After the constant voltage (CV) mode is activated, the battery reaches its full charge voltage. However, it is not yet fully charged. At this stage, the trickle charge mode begins, ensuring the remaining battery capacity is charged while balancing the cells. The battery pack is considered fully charged when all cells are balanced, and the charging current nears 0.05C.
Importance of the Charge-Discharge Curve: The charge-discharge curve of a lithium-ion battery is a critical indicator of its performance. A flat discharge curve is particularly desirable because it reflects a stable voltage throughout the discharge process. This stability ensures consistent energy delivery, which is vital for electric vehicles.
However, a flat discharge curve may limit the depth of discharge (DoD) since the battery system cuts off when one of its cells reaches the lower cut-off voltage. Understanding this curve helps optimize battery use and enhance vehicle performance.
Cycle Life of Lithium-Ion Cells: The cycle life of a lithium-ion cell refers to the number of complete charge-discharge cycles it can undergo before its capacity decreases to 80% of the original. Industry standards suggest maintaining a DoD of 80% for cycle life testing, as reducing the DoD extends the battery’s lifespan.
As India moves toward its ambitious zero-emission mobility goals, understanding the charge-discharge curve and other aspects of lithium-ion batteries becomes increasingly important. Insights into their charging process, discharge curves, and cycle life can significantly contribute to achieving efficient and sustainable electric mobility.
