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Battery Management System

Sandesh Upadhyay

Introduction

A battery management system (BMS) is an electronic regulator that monitors and controls the charging and discharging of rechargeable batteries. Battery management systems of various types are used in most devices that use rechargeable batteries. Lithium-ion batteries are used in multiple applications, ranging from personal electronic devices, like cell phones, to the emerging class of electric vehicles. Because of the fragile nature of these types of batteries, when compared to lead-acid, or NiCd batteries, comparatively advanced monitoring is necessary for safe operation.



Block diagram battery management system




Classification Of BMS 

  • Centralized BMS
  • Distributed BMS
  • Modular BMS

Function of BMS 

1. Primary Function:

The primary function of the BMS is to protect the battery cells from damage caused by being overcharged or over-discharged. 

2. Secondary Function:

  • Parallel cell auto control
  • Cell voltage is constantly monitored
  • An active system can control the charge.
  • Main power voltage.
  • Battery or cell voltage.
  • Charging and discharge rates.
  • Temperatures of the batteries or cells.
  • Battery and cell health.
  • Coolant temperature and flow for air or liquid cooling. 

Working principle 

The intricacy of the electronic components on board determines how well a battery management system works. Let’s take a closer look at how it works by examining a typical BMS with the bare minimum of components for optimal performance. The BMS’s microprocessor monitors the cell voltage and current in real-time and changes the MOSFETs accordingly.

For charging and discharging, the BMS employs only one bus. There is no current flow at first since both charging and discharging FETs are turned off. The BMS’s microprocessor detects the voltage at the input and activates the charging MOSFET, which re-charges the battery. If no voltage is available at the input pin, the BMS assumes the load is connected and activates the discharging FET.

In most BMSs, there are two forms of cell balancing:

       i.            Passive cell balancing

      ii.            Active cell balancing

Bypass resistors are used in passive cell balancing to discharge excess voltage and equalize with other cells. The excess charge of one cell is transferred to another cell with a low charge in the active cell balancing to balance the charges. Charge-storage capacitors and inductors are used.

Why Battery Management System?

  • Heart of all types of energy storage technology.
  • Ensures optimum usage of the energy inside the battery powering the portable/stationary system.
  • The risk of damage inflicted upon the battery is minimized.
  • Enhances system run-time reliability.
  • Increase overall system efficiency.

 

Applications:

  • Mobile
  • Laptop
  • Grid Power Infrastructure
  • Electric Vehicles
  • Industrial machines
  • Electric train traction batteries
  • Garbage compressors
  • Lifts and cranes

 

References:

  • https://www.cselectricalandelectronics.com
  • Lelie, Markus, et al. "Battery management system hardware concepts: An overview." Applied Sciences 8.4 (2018): 534.
  • Chatzakis, John, et al. "Designing a new generalized battery management system." IEEE Transactions on Industrial Electronics 50.5 (2003): 990-999.











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