What is BMS

battery management system (BMS) is any electronic system that manages a rechargeable battery (cell or battery pack), such as by protecting the battery from operating outside its safe operating area[clarification needed], monitoring its state, calculating secondary data, reporting that data, controlling its environment, authenticating it and / or balancing it.[1]

A battery pack built together with a battery management system with an external communication data bus is a smart battery pack. A smart battery pack must be charged by a smart battery charger.

Battery Management Unit (BMU)

The BMU is a bridge between the CMUs and the vehicle communication bus. It controls the pre-charge and main contactors of the battery pack as well as collating the telemetry data from the nodes and providing a summary to other components on the vehicle CAN bus.

BMS Tech

How is The BMS Works

The Orion Battery Management System (BMS) performs three primary functions:

  • It protects the battery pack from being over-charged (cell voltages going too high) or over-discharged (cell voltages going too low) thereby extending the life of the battery pack. It does this by constantly monitoring every cell in the battery pack and calculating exactly how much current can safely go in (source, charge) and come out (load, discharge) of the battery pack without damaging it. These calculated current limits are then sent to the source (typically a battery charger) and load (motor controller, power inverter, etc), which are responsible for respecting these limits.
  • It calculates the State of Charge (the amount of energy remaining in the battery) by tracking how much energy goes in and out of the battery pack and by monitoring cell voltages. This value can be thought of as a fuel gauge indicating how much battery power is left in the pack.
  • It monitors the health and safety of the battery pack by constantly checking for shorts, loose connections, breakdowns in wire insulation, and weak or defective battery cells that need to be replaced.

There are also secondary functions that the BMS performs:

  1. Balances all the cells in the battery pack by intelligently bleeding off excess energy from cells that are charged more than others. This provides the maximum amount of usable energy (capacity) from the battery pack since the pack is only as strong as the weakest cell.
  2. Monitors the temperature of the battery pack and controls a battery fan to regulate the temperature of the pack. Additionally, it constantly monitors the output of the fan to make sure it is working properly.
  3. Provides real-time information and values to other devices such as motor controllers, chargers, displays and data loggers using several different methods (CANBUS, analog outputs, and digital outputs).
  4. Stores error codes and comprehensive diagnostic information to aide in fixing problems with the battery pack should any issues arise.

li ion battery BMS