In addition to the essential protective functions, a battery management system (BMS) offers a range of other functions aimed at optimizing capacity utilization, extending service life and displaying capacity to the customer. These advanced functions contribute significantly to the efficiency and performance of the battery system.
Cell balancing is used in battery packs with several serially connected cells to equalize the charge states of the individual cells. Differences in temperature and internal resistance can lead to uneven states of charge, which affects the overall performance of the battery pack. Balancing prevents the weakest cell from limiting the performance of the entire battery pack by undercharging or overcharging it prematurely. This extends the service life of the battery and improves capacity utilization.
To determine the exact capacity of the battery pack, a BMS has a gas gauge system. This function determines the total capacity and the remaining capacity of the battery pack. The gas gauge system is complex and must be precisely matched to the respective application in order to deliver accurate results. The current profile of the end application and user behavior play a decisive role in this. This precise capacity display helps the user to better estimate the remaining operating time of the battery and thus optimizes the use of the battery.
The BMS offers various BUS systems for reading out the data. The most common include I2C, SMBus, CAN, LIN and RS232. These systems enable simple and efficient data communication between the battery pack and other system components. The use of a BUS system facilitates the integration of the battery pack into various applications and supports the monitoring and control of the system in real time.
For low-power systems, it may make sense to integrate the charger directly into the BMS. This has the advantage that the charger can also be adapted when cells are changed, ensuring backwards compatibility with older systems. This integration saves space and reduces the complexity of the overall system by eliminating the need for external chargers.
In systems in which the battery plays a central role, additional system functions can be integrated into the battery. This makes it possible to save on a second intelligence, such as a microcontroller. For example, motor control and battery protection circuitry can be combined in the battery, making the control microcontroller (μC) and the duplicate design of the power FETs (field-effect transistors) superfluous. This integration simplifies the design of the overall system and improves efficiency and reliability.
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