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Electronic manufacturing industry
What is BMS – A Comprehensive Guide

According to Marklines statistics, the total global sales of electric vehicles in 2020 was 2,892,400, a year-on-year increase of 45%.

Today, with the rapid popularization of electric vehicles, battery life and safety issues are still a problem that plagues consumers and manufacturers.

How to manage batteries scientifically and effectively has become a breakthrough point for many new energy battery manufacturers to attack.

Under the background and trend of the industry, BMS (Battery Management System) has become the key development direction of the industry. As an important link connecting onboard batteries and electric vehicles, BMS can estimate the state of charge of the battery in real-time, detect the state of use of the battery, and directly control how the battery functions.

In addition, BMS also needs to exchange information with the vehicle system to solve key issues such as safety, usability, ease of use, and service life in the lithium battery system.

Statistics show that the global BMS output value exceeded US$6 billion in 2020, and is expected to reach US$11.17 billion in 2025, with a compound growth rate of 11.6% from 2017 to 2025.

Table of Contents

What is BMS?

BMS is the abbreviation of Battery Management System. BMS is a device that cooperates with monitoring the status of energy storage batteries. It is mainly for intelligent management and maintenance of each battery unit, to prevent overcharging and over-discharging of the battery, to prolong the service life of the battery, and to monitor the status of the battery. Generally, BMS is represented as a PCB or a hardware box.

Battery Management System
Battery Management System

BMS is one of the core subsystems of the battery energy storage system. It is responsible for monitoring the operating status of each battery in the battery energy storage unit to ensure the safe and reliable operation of the energy storage unit. 

The BMS can monitor and collect the state parameters of the energy storage battery in real time (including but not limited to the voltage of the single battery, the temperature of the battery pole, the current of the battery circuit, the terminal voltage of the battery pack, the insulation resistance of the battery system, etc.), and carry out necessary analysis and calculation on relevant state parameters to obtain more system state evaluation parameters, and realize effective control of the energy storage battery body according to a specific protection control strategy to ensure the safe and reliable operation of the entire battery energy storage unit. 

At the same time, BMS can exchange information with other external equipment (PCS, EMS, fire protection system, etc.) through its own communication interface, analog/digital, input/output interface, and form a linkage control of each subsystem in the entire energy storage power supply system to ensure safe, reliable and efficient grid-connected operation of the power supply system.

The reason why BMS is so important is that battery mileage, fast charging, cost and safety testing are all closely related to the optimization of BMS.

BMS architecture

From the perspective of topology, BMS is divided into two types: Centralized and Distributed according to different project requirements.

Centralized BMS
To put it simply, the centralized BMS collects all batteries with one BMS hardware, which is suitable for scenarios with few batteries.

Centralized BMS
Centralized BMS

Centralized BMS has the advantages of low cost, compact structure, and high reliability. It is generally used in scenarios with low capacity, low total voltage, and small battery systems, such as electric tools, robots (handling robots, power-assisted robots), IOT smart homes ( Sweeping robots, electric vacuum cleaners), electric forklifts, electric low-speed vehicles (electric bicycles, electric motorcycles, electric sightseeing cars, electric patrol cars, electric golf carts, etc.), light hybrid vehicles.

BMS hardware with a centralized architecture can be divided into high-pressure areas and low-pressure areas. The high-voltage area is responsible for collecting the voltage of the single battery, collecting the total voltage of the system, and monitoring the insulation resistance. The low-voltage area includes power supply circuit, CPU circuit, CAN communication circuit, control circuit, etc. With the continuous development of passenger car power battery systems to high capacity, high total voltage, and large volume, BMS with distributed architecture is mainly used in plug-in hybrid and pure electric vehicles.

Distributed BMS
In a distributed system, the measurement unit and other electronic devices are directly installed on the circuit board integrated with a single battery. The advantage of this is that compared with the previous few, the connection between the BMS and the single battery is basically used wiped out.

Centralized and distributed BMS architectures
Centralized and distributed BMS architectures

Distributed BMS has many advantages:

  • The first is to have extremely high scalability, which can be extended down to a single battery.
  • Secondly, the connection reliability is high, basically, there are no excessively long cables, and the batteries and the measurement circuit are closely integrated, which also reduces interference and errors. Security is also high.
  • It is also easy to maintain, as only a small unit needs to be replaced if something breaks.

But there are also some shortcomings:

  • The cost is very high. Because each unit has an additional set of equipment, the overall cost is very high.
  • The volume is too large. There is a measurement system next to each cell of each battery, which will affect the volume of the entire battery panel.

Functions of BMS

Functions of BMS
Functions of BMS

1. Overcharge protection

During the charging process of the lithium battery, lithium atoms flood into the safe house, but if lithium ions continue to pour into the safe house when it is full, the safe house will inevitably become very crowded, and there will be many uncertain dangers arising.

The overcharge protection function of the protection board is to monitor the voltage of the battery pack in real time. When the charge reaches the peak of the safe voltage range, it will cut off the power supply to maintain the order of the safe house.

2. Over-discharge protection

During the discharge process of a lithium battery, the voltage will gradually drop. If the battery voltage is completely exhausted, the internal materials of the batteries will lose their activity, and in the worst case, the batteries will fail.

The over-discharge protection function of the protection board is to monitor the voltage of the battery pack in real-time. When the discharge reaches the over-discharge voltage of the batteries, it will cut off the power supply to prevent the voltage from continuing to drop.

3. Overcurrent protection

The overcurrent protection function of the protection board is to monitor the current of the battery pack in real-time during the charging and discharging process. When the current exceeds the safe range, the flow of the current is cut off to prevent the batteries or equipment from being damaged by excessive current, thus playing a protective role.

Conclusion

In this article, we have offered detailed information about BMS (Battery Management System), including what BMS is, its architecture, and its functions. For more, you can read other posts in our website, such as battery PCB, etc.

FAQ

BMS is the abbreviation of Battery Management System. BMS is a device that cooperates with monitoring the status of energy storage batteries. It is mainly for intelligent management and maintenance of each battery unit, to prevent overcharging and overdischarging of the battery, to prolong the service life of the battery, and to monitor the status of the battery.

  • Centralized BMS
  • Distributed BMS
  • 1. Overcharge protection
  • 2. Over-discharge protection
  • 3. Overcurrent protection

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