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Battery Management System

A Battery Management System (BMS) is analogous to human brain and manages the overall health of a battery pack. Its role is to manage the output, charging and discharging and notify on the status of the battery pack. It is responsible to provide critical safeguards to limit damage to battery systems. There are three primary functions that a BMS performs:  

Cell protection

This is the most important and a critical task that a BMS performs. It performs protection against charging and discharging. BMS protects the cells from cell voltages going too high (over-charging) or over-discharged i.e. voltages going too low. This helps in extending the life of the battery pack. BMS monitors every cell in the battery pack to figure out safe inflow and outflow of current without damaging the battery pack. The concept of cell protection can be understood in the context of Li ion batteries. In case of a Li ion battery, if overcharged it can get overheated thereby becoming damaged leading to explosion. In such cases a BMS provides over voltage protection. Similarly, If discharged below a point, Li ion cells can be damaged and lose their capacity. To ensure a Li ion battery's charge doesn't go above or below its limits, a battery management system has a safeguard device called a Lithium-ion protector.  

Energy Management

The second most important function performed by a battery management system is energy management. BMS manages energy in two ways. It tracks energy inputs into the battery pack and out of the battery pack and also by monitoring cell voltages. Energy management feature can be analogized with a fuel gauge indicating how much battery power is left in the pack.  

Proactively monitors the health and safety of the battery pack

BMS’s proactively checks for shorts, loose connections and breakdowns in wire insulation to identify defective battery cells that need to be replaced.  

Secondary functions of the Battery Management System

  • Cell balancing in the battery pack: BMS does this by withdrawing excess energy from overcharged cells. This maximizes the usable energy (capacity) from the battery pack.
  • Monitoring the temperature of the battery pack: BMS constantly monitors the battery fan and controls it to regulate the temperature of the pack.
  • Provision of real-time data: Real time data can be given by BMS to motor controllers, chargers, displays and data loggers using several different methods (CANBUS, analog outputs, and digital outputs).
  • Stores error codes and comprehensive diagnostic information BMS aids in fixing overall problems with the battery pack if any issues arise.
 
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