A lithium ion battery for an electric vehicle may consist of 1,000 or more individual cells. At the present time, each cell must have a voltage sensor and one or more current sensors. They provide feedback to the battery management system to help balance the charge in individual cells and prevent the cells from overheating. Lithium ion battery cells that get too hot may explode or burst into flames.
Philip Dost is an engineering student at Ruhr-Universität Bochum in Germany. His specialty is power system technology and power mechatronics. He is part of a team that has developed a new system that reduces the number of individual sensors needed to manage a battery pack. The new technology may make future lithium ion batteries for EVs lighter, smaller, and cheaper. Dost says, “Just like the cells, the sensors are a considerable weight and cost driver.”
The new technology reduces the number of sensors needed to one for current and one for voltage regardless of the number of cells the battery pack has. The sensors also perform cell balancing functions, something that normally requires a separate system.
Cell balancing is necessary to maintain the maximum energy yield of EV batteries, especially as they age Dost says. Each cell reacts differently during charging and discharging. By the end of the process, some are charged more than others. Once one cell is fully charged, charging of the other cells stops. Such an imbalance can cause degradation in performance in older batteries. Cell balancing can counteract such deterioration and keep older batteries working efficiently according to Dost.
The sensor system developed by the team is scalable and can be applied to any lithium ion battery whether it is designed to power an EV or a tablet, laptop, wireless electrical tool, uninterruptible power supply, or solar energy storage systems. The engineering team is beginning to attract interest from mainstream manufacturers and is continuing to develop their prototype to meet the requirements of the automotive industry.