The role of the BMS in lithium-ion batteries
Lithium-ion batteries offer numerous advantages, particularly in terms of energy density and lightweight design. Widely adopted in portable everyday devices, electric vehicles, e-bikes, and stationary energy storage systems, they have become an essential technology.
These batteries consist of cells connected in series and are equipped with an electronic system called the Battery Management System (BMS). This electronic board is vital for ensuring safety and optimizing the lifespan of lithium-ion batteries. A high-quality BMS protects battery cells from potential overcharging or overvoltage.
In this article, Batteries Prod explains the BMS’s role in lithium-ion batteries in a simple and clear manner.
What is the role of the Battery Management System in lithium-ion batteries?
Battery management systems (BMS) are designed to adapt to different battery technologies, meeting the specific needs of various applications.
These electronic boards regulate key parameters, extending the life of lithium batteries. The BMS consolidates information from all cells, such as current, voltage, and temperature.
The BMS is typically a variable-sized circuit board connected to all the cells. It performs essential safety functions, preventing short circuits, overvoltage, undervoltage, and abnormal temperatures.
Monitoring lithium-ion batteries
Lithium cells are sensitive and must not be exposed to extreme conditions, such as high voltage, high temperatures, or physical shocks. Since the electrolyte in lithium-ion batteries is liquid, they are at risk of short circuits.
The BMS interrupts charging or discharging processes to avoid damage that could shorten the battery’s lifespan. It ensures uniform charging across all cells, protecting them from overvoltage or undervoltage.
The BMS also provides intelligent battery monitoring, tracking metrics such as state of health, state of charge, depth of charge…
The “cell balancing” function
Over time, due to charging and discharging cycles, imbalances can develop between the cells of a lithium-ion battery.
This imbalance can lead to differences in performance among cells, depending on usage conditions or battery state. Consequently, some cells may charge fully while others only partially, reducing the overall energy capacity of the battery. This phenomenon accelerates aging in some cells, ultimately shortening the battery’s lifespan. This is where the BMS plays a crucial role.
Two cell-balancing strategies are employed: passive balancing and active balancing. The passive balancing aims to discharge the cells with the most energy in order to match their charge level with the rest of the cell group. Active balancing, on the other hand, involves transferring energy from the cells with the highest energy to the weaker cells.
Lithium battery cells need to be balanced during charging to ensure they reach a similar voltage at the end of the cycle. The BMS carefully monitors and controls the state of charge for each lithium-ion cell. By leveraging this electronic system, the battery pack’s capacity is maximized while degradation is minimized. The BMS plays a critical role in correcting charge imbalances across all cells, ensuring consistent performance and extended battery life.