Electric Battery Management

Electric battery management encompasses cell monitoring, charging and discharging control, temperature control, fault analysis, and data acquisition to improve the performance of batteries in electric vehicles, ultimately achieving the automotive grade (AG).

Battery in EVs

Battery electric vehicles (BEVs) source energy from a lithium-ion (Li-ion) battery pack made of thousands of individual cells.

 An illustration of how battery cells are arranged into modules and then assembled into battery packs

Unlike lead-acid or nickel-cadmium-based batteries, Lithium-ion batteries come with maximum energy density and a high life cycle. This brings an incentive for manufacturers to save space with the provision of increased capacity.

Many factors influence the capacity of the battery packs and battery life including overcharge and discharge current, thermal runaway, over-voltage, or under-voltage. One important factor that contributes to decreased capacity is an imbalance in the cell voltage of these battery packs.

A battery management system (BMS) ensures the operation of the battery within its safe limits.

Battery Management System

  • BMS monitors the state of charge (SOC) and state of health (SOH) of electric battery packs in real-time, serving as a vehicle fuel gauge assistant 
  • It determines the SOC of an electric battery by using various algorithms. Since an electric battery is based on various Li-ion cells, it is the job of a battery management system to ensure that the cells will not be discharged completely, hence, ensuring the cell balancing. The safe limit of electric current retention is 3V
  • SOH is another area where a BMS significantly contributes towards safe operations by measuring the expected age of the battery and helping in determining the mileage on each charge
  • Processes such as charging control work simultaneously during real-time monitoring. An intelligent system determines the constant current and constant voltage of a battery for a seamless operation.

The following table provinces the key elements of battery management systems. 

Power ManagementIt comprises of protection circuit for power supply and voltage regulator to maintain a constant voltage even when there is  variation in supply power
HV Power InterfaceIt is a high-side driver used for automotives and contains MultiSense analog feedback 
Interface between battery management and control unitIt is a serial peripheral interface (SPI) that serves as a communication link between devices in various voltage domains
Battery Management UnitIt is responsible for the protection as well as monitoring of each cell of the battery to ensure its reliability
Control UnitIt comprises of control logic, various registers (data, address, shift) and memory array 
Wired ConnectivityIt comprises of a bidirectional Can bus transceiver

Supporting Documentation

  1. https://ieeexplore.ieee.org/document/8959965
  2. https://www.nature.com/articles/d41586-021-02222-1
  3. https://onlinelibrary.wiley.com/doi/full/10.1002/est2.203
  4. https://www.einfochips.com/blog/understanding-the-role-of-bms-in-electric-vehicles/
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