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Power cell safety PACK and BMS are key

Source: TOPAK POWER Pageview: 118 Release Date: 2020-07-02

Benefit from the domestic policy to support the development of new energy vehicles and lithium power battery industry, 2015 new energy vehicle production and sales increased dramatically, power battery supply exceeds demand, policy dividends benefit the entire industry chain. Industry insiders expect that 2016 will usher in the first year of the development of power batteries.

There is no doubt about the long-term trend of power battery applications, but the safety performance is the primary criterion for consumers to choose products. Recently, the Ministry of Industry and Information Technology “stopped” ternary lithium batteries, new energy bus fire spontaneous combustion accidents, 5,561 Volkswagen Golf pure electric for “battery management system problems” recall and other events have occurred one after another, once again triggered the public on the safety of power battery safety performance Concern.

For the safety of the power battery, in addition to the battery material technical route controversy, the industry generally believes that the role of PACK and BMS in ensuring battery safety is irreplaceable.

The power battery PACK consists of three parts, namely, battery module, BMS and fixed frame shell (covering thermal management, structural design, high-voltage control, safety management, etc.). The BMS is called the “brain” of the EV power battery system, and together with the power battery and vehicle control system, it constitutes the three core technologies of EV.

BMS (Battery Management System) is the core of the battery pack, which is needed to control and optimize the balance of charge, service life and safety, etc. In the new energy vehicle industry chain, the industrial value of BMS is very important.

Publicly available information shows that the BMS has functions such as preventing overcharging, avoiding over-discharge, temperature control, keeping the voltage and temperature of the battery components balanced, and predicting the remaining battery charge and remaining driving range. At the same time, BMS also has the ability to monitor and adjust the battery management status in real time, and the ability to work synchronously with multiple parallel subsystems. The BMS can accurately measure the battery pack usage, protect the battery from overcharging and discharging, balance the power of each battery in the battery pack, and analyze and calculate the battery pack power and convert it into understandable range information to ensure the safe operation of the power battery.

In the 2016 national “new energy vehicle” pilot project document issued by the Ministry of Science and Technology, power batteries and battery management systems are listed as key research tasks, among which, “charging facilities to meet the demand for BMS protection response rate of 100%” is listed as one of the evaluation indicators of the electric vehicle infrastructure operational safety and interoperability technology.

Although BMS is very important for electric vehicles, but due to the relatively low proportion of the vehicle cost, has long not been the importance of the vehicle enterprises, lack of design and production experience, to do better and stronger BMS products, domestic enterprises in the field of power battery BMS still have a long way to go, but due to the sudden outbreak of production and sales of new energy vehicles, the rapid expansion of the downstream application market did not give BMS Enough time for the industry to grow. A research report predicts that by 2020, the market size of power batteries for vehicles will reach 120 billion yuan. Among them, the BMS systems used in passenger cars will account for about 10%-16%, and those for commercial vehicles will account for about 3%-5%, when the market size of domestic BMS for electric vehicles will reach 17 billion yuan.

Along with the significant expansion of lithium battery production capacity, the market demand for BMS, BYD, Guoxuan high tech and other vehicle enterprises, electric core enterprises also began to layout BMS field. Battery companies and vehicle companies are accelerating the market share, PACK companies also have a set of their own way of survival.

“Although BMS accounts for a relatively low percentage of the total vehicle cost, it is important to ensure the safety of power batteries. pack companies want to survive by virtue of the core technology of BMS, the solution strength of the entire solution of BMS and the service capability.”

【BMS】

1、Based on the temperature sensor (each small module has a temperature sensor) and smoke sensor, it determines the battery abnormality, sends a timely warning signal to the driver, and then cuts off the vehicle’s high-voltage system.
2、Detect abnormal resistance of the power battery, and when an abnormal change in circuit resistance is detected (loose connector/loose screw generation/battery abnormality), promptly initiate an alarm to the driver and cut off the high voltage.
3、The remote monitoring system will determine the battery status based on the transmitted parameters and empirical models and provide timely feedback to the end system.

【PACK】

The perceived insecurity of power batteries is essentially due to the inadequacy of current batteries, and the following measures are taken in terms of PACK design  :

1, the choice of the single is more important, the battery safety is good, not easy to catch fire and explode the battery.
2、Add automatic fire extinguisher to automatically extinguish the fire when the fire source is detected.
3、Add pressure relief valve to prevent the accumulation of pressure in the battery box.
4、High temperature resistant flame-retardant materials are selected for the battery case and module.
5、For each type of battery, we will do combustion test of the module to ensure that it will not catch fire and explode when the high temperature burns.
6, CAE thermal design of the battery box, a well-designed thermal management system to prevent the battery box from overheating in the high-temperature environment.
7、Select to use anti loosening bolts.

Who is in charge of power cell safety? Getting the PACK and BMS right is key

13年锂电池定制厂家