Battery Management Systems (BMS) are critical to the safe, dependable, and efficient operation of lithium-ion batteries. It is an electronic supervisory system that maintains the battery pack by measuring and monitoring cell parameters, calculating cell status, and safeguarding cells by running them in the Safe Operating Area (SOA).
LV battery packs are commonly found in light electric and hybrid cars, as well as two and three-wheelers. HV battery packs are commonly utilized in propulsion applications for electric vehicles as well as stationary applications in Energy Storage Systems (ESS).
HV battery packs are made up of a large number of lithium-ion cells that are coupled in series and parallel to provide the pack’s total voltage. For example, a 600V, 100kWh hybrid bus HV battery pack made of 18650 NMC cells will contain around 160 cells in series and 55 cells in parallel, bringing the total cell count to 8800.
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Centralized BMS Architecture
One central pack controller monitors, balances, and controls all cells in a centralized BMS. The complete device is contained in a single assembly, from which the wire harness (N + 1 wires for N cells in series and temperature sensing wires) connects to the battery’s cells. These cables are used for measuring cell voltage, temperature, and balance.
The board is often powered by the battery output and does not need an additional power supply. As part of the cell monitoring circuitry, it has several Analog to Digital Converters (ADC) channels. The voltage on each cell is referred to as the BMS ground, and this voltage rises with the number of cells, providing a high voltage at the ADC channels measuring the topmost cells in the stack.
Decentralized BMS Architecture
Fundamentally, a decentralized BMS does not contain the full cell monitoring and intelligence circuitry on a single assembly. This architecture may be constructed using the following topologies:
- Modular: The battery management system is separated into many, identical modules, each with its own bundle of wires that connects to one of the batteries in the pack. Typically, one of the modules is identified as the master since it administers the entire pack and communicates with the rest of the system, while the others serve as basic remote measurement devices.
- Master-Slave: This architecture is made up of the Master and Slave BMS components. A collection of battery cells within the battery module are monitored, balanced, and controlled by the slave unit. A communication interface connects it to the master unit.
- Distributed: A distributed BMS is distinct from the other topologies. In other topologies, the electronics are grouped and housed away from the cells; in a distributed BMS, the electronics are stored on cell boards that are put directly on the cells being monitored.
Conclusion
BMSs are crucial in guaranteeing battery pack safety. It is becoming increasingly important to develop and integrate a suitable BMS for high voltage lithium-ion batteries into autos and energy storage systems. A decentralized BMS is ideal for these high voltage battery packs.
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