With the maturity of lithium-ion battery technology, electronic equipment, power tools, low-speed 4-wheel electric vehicles, electric scooters, etc. are driven by the latest lithium batteries. Thanks to the high energy density of lithium-ion batteries, they are equipped with batteries of the same capacity. The size and weight of the product have been greatly optimized, and a 5 kg lithium-ion battery pack is enough to drive an electric scooter for dozens of kilometers. The lithium-ion battery management system BMS is a product derived from the development of lithium-ion batteries. The application of BMS makes the clean energy of green lithium batteries safer, prevents overcharge and overdischarge of the battery, prolongs the service life of the battery, and monitors the battery. status. BMS became the steward of lithium batteries.

This article elaborates on the battery management system (BMS), so that people who lack knowledge of battery management systems can understand the basics of BMS.

First of all, what is a battery management system, referred to as BMS, sometimes called a battery protection circuit board?

The BMS battery management system is called a battery nanny or a battery housekeeper. Its main function is to control the charging and discharging process of the battery by collecting and calculating parameters such as voltage, current, temperature, and SOC, monitor the battery status, and prevent the battery from overcharging and Over discharge ensures the safe use of lithium batteries and prolongs the service life of the batteries.

Reference article:Battery management system     What is a battery management system

What are the benefits of using BMS?

1. Increase the service life of the battery

High-temperature environment, low-temperature environment, and depth of discharge are the main factors that cause damage to lithium-ion batteries. Over-discharge will cause permanent damage to lithium-ion batteries. The lithium battery management system protects the lithium battery from these factors by controlling the battery's operating temperature, charge cut-off voltage, discharge cut-off voltage, and discharge current, thereby increasing the service life of lithium-ion batteries.

2. Security

Due to the material characteristics of the lithium battery itself, it cannot be overcharged, over-discharged, over-current, short-circuited, and ultra-high temperature charge and discharge. Overcharge, over-discharge and over-discharge will cause the lithium battery to burn and explode. Now mobile phone lithium has appeared. Cases of human casualties caused by battery explosion, therefore lithium batteries must be used together with the lithium battery management system, and the role of the battery protection board and battery management system is to strictly control the charging and discharging of the battery and temperature control to make it operate within a safe range.

3. Improve the efficiency and performance of the battery pack

Since the lithium-ion battery pack is composed of multiple cells, each cell will have differences in rated capacity, internal resistance, self-discharge, built-in differences, and inconsistencies in single cells. An important factor in the performance of a battery pack. There are so many cells working together, but the overall performance of the battery pack is actually determined by the worst cell, which is what we often call the barrel principle. A very important function of the lithium battery management system is the equalization function. Through the management of the battery management system, the parameters of the single cells tend to be balanced, thereby improving the performance and efficiency of the battery pack.

Reference article: Overview of cell balancing methods for Li-ion battery technology

Common features of BMS:

1. Voltage measurement and protection (required function)

Like an ordinary ternary lithium-ion battery pack, once it detects that the voltage of any battery exceeds 4.2V or the voltage of any battery is lower than 3.0V, the battery management system will automatically cut off the charging or discharging circuit, thereby protecting the battery from further damage .

2. Communication function

Different systems have different requirements for communication interfaces. The mainstream communication interfaces include SPI, I2C, UART, CAN, RS485, etc. Among them, the automobile and energy storage systems are mainly CAN and RS485.

Reference article:The difference between I2C SPI UART and CAN

3. SoC estimation

SOC calculation, battery power calculation is a very important part of BMS, many systems need to know the remaining power situation more accurately. Due to the development of technology, many methods have been accumulated for SOC calculation. The remaining power can be judged according to the battery voltage if the accuracy is not high. The main accurate method is the current integration method (also called Ah method), Q = ∫i dt, and There are internal resistance method, neural network method, Kalman filter method, etc. The mainstream in the industry is still the current integration method.

4. SoH estimation

State of health, can be understood as the percentage of the current capacity of the battery to the factory capacity, the new factory battery is 100%, and the complete scrap is 0%. The lower the SOH, the greater the internal resistance of the lithium-ion battery. The internal resistance of the battery is indirectly calculated by detecting the voltage, current, temperature and other data, and then the SOH is calculated according to the relationship between the SOH and the internal resistance of the battery.

5. Exception warning

6. Abnormal protection

7. Single cell balance

Generally, there are two types of passive balancing and active balancing. Passive balancing is mainly to balance the power with more power through resistance consumption. Active balancing is mainly to transfer the power of the battery with more power to the battery with less power through the capacitor, inductance or transformer. Achieve equilibrium. Because the active balancing system is relatively complex and the cost is relatively high, the mainstream is still passive balancing.

8. Other control circuits (such as battery loop relay control)

9. Temperature measurement

10. Current measurement

11. Status diagnosis

During the battery charging and discharging process, the terminal voltage and temperature of each battery in the battery pack, the charging and discharging current and the total voltage of the battery pack are collected in real time to prevent the battery from being overcharged or overdischarged.

12. With charger to provide corresponding charging strategy

13. Real-time display of various data

Main functional modules of BMS:

1. Hardware layer, sampling and measurement functions (basic information sampling voltage, temperature, current, etc.)

2. Intermediate layer, state estimation and prediction functions (electrical characteristics state estimation SOC, SOH, etc., temperature and safety characteristics state estimation, battery internal temperature, leakage current, etc.)

3. Application layer, control and management functions (balance management, passive balance, active balance, discharge management, charge management, power limit)

4. Application layer, communication and diagnostic function application layer (communication, CANBUS, UART, I2C, RS485, etc., fault diagnosis, fault handling, data recording)

How should I choose BMS? —The information you need to confirm before choosing the right BMS

1. The type of battery, ternary lithium battery, polymer lithium battery, lithium iron phosphate battery, lithium titanate battery, lithium manganate battery, lithium cobalt oxide battery, etc.

2. The number of strings, voltage and capacity of the battery.

3. The continuous discharge current and maximum discharge current of the battery (usually 2 times the continuous discharge current).

If you have determined the above parameters of your battery, and you still have a lot of questions about how to choose BMS, you can contact us, our engineers will analyze your needs and provide you with the best BMS solution, which can provide you with current Some mature BMS solutions can also be customized for you. Click here to send the message.

What are the main application areas of the lithium battery protection board and battery management system?

1. Battery protection board (PCM: Power Circuit Module) or Battery protection board is mainly used in consumer electronic products such as cameras, mobile phones, and laptops.

2. Battery Management System (BMS: Battery Management System) is mainly used in power battery packs, such as electric vehicles, electric scooters, energy storage and other larger power battery systems.

Wiring diagram of 20 series battery pack protection board (same port for charging and discharging)

With the application of lithium-ion batteries, battery management systems have become popular. We all need to have some knowledge of BMS. Hope this article can improve your understanding of battery management system. If you have any questions, you can leave a message on our website. We have a team of more than 20 engineers who have rich experience and technology to provide you with the most professional answers.

LTW company has various types of BMS to choose from, from 1S-24S BMS, "S" represents the number of batteries. From the hardware version of the BMS to the software version of the BMS. At the same time, due to our relationship with the lithium battery industry, we cooperate with a large number of battery factories to provide customized services for lithium battery packs. Therefore, this means that you can customize BMS and battery packs with us! At LTW, we have a series of BMS available for you to use. Don't forget to click here to check them!

Here are our mature BMS solutions, welcome your inquiry