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Fundamental Understanding of Battery Management System

A Battery Management System (BMS) is an electronic system that manages and monitors the charging and discharging of rechargeable batteries. A given BMS has many different objectives such as: I/V (current/voltage) monitoring, cell balancing, temperature monitoring, over-current protection and short circuit protection, etc. However, in this series, we will take a closer look at I/V monitoring and balancing functionalities.



Understand the Essentials and Innovations in BMS


A Battery Management System (BMS) is a system that manages and monitors the performance of rechargeable batteries, such as those used in electric vehicles, solar power systems, PSUs (Power Supply Units), remote data centers and portable electronics. The growing trend of devices that require recharging, including Electric Vehicles (EVs) and E-scooters, is driving the exponential growth of the global BMS market.


The main objective of BMS is to ensure safety, longevity and efficiency of the batteries by regulating its charging and discharging and monitoring the state of charge (SOC) and state of health (SOH) of each individual cell within the pack. The BMS prevents overcharging, over-discharging and overheating. Additionally, the BMS can provide information about the battery pack's performance and health to the user or system controller, and even the manufacturer.


In this two-part series, we will discuss basics of battery management systems, main functionalities and two main objectives of any given battery management system: monitoring and balancing. In part one, we will discuss various common monitoring method. Part two will focus on different balancing options.


Monitoring


In a BMS, monitoring refers to the process of continuously measuring and analyzing various parameters of the battery pack to ensure its safe and efficient operation. These parameters include voltage, current, temperature, state of charge (SOC), state of health (SOH) and other relevant data. As was mentioned above, the BMS uses this information to make decisions about charging, discharging and balancing the battery cells to prevent overcharging, over-discharging, overheating and other potentially dangerous conditions. The monitoring function is critical for maintaining the performance, reliability, efficiency and safety of the battery cells.


There are three main methods of monitoring any given battery’s SOC:


  • Voltage measurement method:


  • Coulomb counting method:


  • Ohmic or impedance measurement:


Now that we have a good understanding of a Battery Management System’s role in monitoring battery cells and different methods of monitoring, we can apply this understanding to pick a right monitoring method for our BMS applications. In part two, we will continue exploring the different balancing architecture and their tradeoffs.


In addition, make sure to check our low voltage BMS reference design. Microchip Technology offers a low voltage BMS solution for various battery chemistries, including lithium-ion, lead-acid and nickel-metal hydride. Our low voltage BMS evaluation platform demonstrates monitoring a stack of 6 to 8 series 18650 Li-Ion batteries using the PAC1952 analog front end. This battery management solution offers state-of-charge determination using all three methods demonstrated in this post: voltage measurement, coulomb-counting and impedance measurement to enable accurate monitoring of battery cells. In addition, this demo supports passive cell-balancing using a network of discrete FETs and resistors. It also comes with GUI support showing battery cells’ SOC in real time.


Iman Chalabi, Dec 7, 2023

Tags/Keywords: Industrial and IoT







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