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Measurement Circuit
Precisely measures each cell's voltage, the pack current and the data from temperature sensors. These are the "sensory organs" of the BMS.
The core parts that make up a BMS and the key concepts you should know.
A battery management system is made up of several main blocks working together.
Precisely measures each cell's voltage, the pack current and the data from temperature sensors. These are the "sensory organs" of the BMS.
Processes the measured data, calculates SoC/SoH, makes protection decisions and runs the balancing algorithms.
Eliminates voltage differences between cells so that maximum capacity can be drawn from the whole pack.
Uses MOSFETs and fuses to disconnect the circuit during overcurrent, short circuit and overvoltage events.
Exchanges data with the main system over CAN bus, UART, RS485 or I²C.
Tracks the temperature at different points of the pack using NTC thermistors.
Key concepts you will encounter often in the world of BMS.
The current percentage to which the battery is filled; similar to a fuel gauge. 100% means full, 0% means empty. The BMS estimates SoC from voltage and current measurements.
Indicates how worn the battery is compared to its new condition. 100% represents a brand-new battery, while lower values reflect aging and capacity loss.
It is natural for series-connected cells to reach different voltages over time. Balancing removes these differences so all cells are used equally. Passive balancing burns off excess energy as heat through a resistor; active balancing transfers energy between cells and works more efficiently.
Shows how much of the battery has been discharged. It is the inverse of SoC: 20% SoC means 80% DoD. Operating at a low DoD extends battery life.
Expresses the charge/discharge rate of the battery relative to its capacity. 1C is the current that fully discharges the battery in one hour. 2C is twice as fast, 0.5C twice as slow.
A dangerous chain reaction in which a cell heats uncontrollably and triggers neighboring cells as well. One of the most important jobs of a BMS is to prevent this by monitoring temperature.