What is Battery Pack?

Classification of battery packs

What is battery pack?  (Battery cell,Battery,Battery pack)

First of all, we must understand the general distinction between lithium battery cells, lithium battery modules and lithium battery packs:

Battery cell: The most basic element that makes up a battery pack and a battery pack, generally the voltage that can be provided is between 3v-4v;

Battery: A collection of multiple cells to form a single physical module that provides higher voltage and capacity;

Battery pack: It is generally composed of multiple battery packs, and at the same time, a battery management system (bms) is also added, which is the final product provided by the battery factory to users.

Composition classification of battery pack:

As the core component of PACK, batteries are currently divided into three main categories based on the shape of batteries: square shell, cylinder and soft pack (polymer battery). The positive and negative electrodes are packaged into the corresponding shells in different ways

Battery module

By assembling single cells, the cells can be connected in series and parallel through bus bars, which can be locked by screws, resistance welding, ultrasonic welding, ultrasonic aluminum wire welding and laser welding.

Considering the production yield, efficiency and the internal resistance of the connection point, laser welding is currently the first choice of many battery manufacturers.

Composition of battery pack

It mainly includes battery module, mechanism system, electrical system, thermal management system and BMS. 

Battery Module

If the battery PACK is compared to a human body, then the module is the "heart", which is responsible for storing and releasing energy to provide power for the car.

Institutional system

It is mainly composed of battery PACK cover, tray, various metal brackets, end plates and bolts, which can be regarded as the "skeleton" of battery PACK, which plays the role of support, mechanical shock resistance, mechanical vibration and environmental protection (waterproof and dustproof) effect.

Electrical System

It is mainly composed of high-voltage jumpers or high-voltage wire harnesses, low-voltage wire harnesses and relays. The high-voltage wiring harness can be regarded as the "large artery" of the battery pack, which continuously transmits the power of the heart of the power battery system to various required components, and the low-voltage wiring harness can be regarded as the "neural network" of the battery pack, transmitting detection signals and control in real time Signal.

Thermal management system

There are four main types of thermal management systems: air cooling, water cooling, liquid cooling, and phase change materials. Taking the water cooling system as an example, the thermal management system is mainly composed of cooling plates, cooling water pipes, heat insulation pads and heat conduction pads. The thermal management system is equivalent to installing an air conditioner for the battery pack.

BMS

Battery management system The battery management system can be regarded as the "brain" of the battery. It is mainly composed of CMU and BMU.

CMU: Cell monitor Unit is a single monitoring unit, which is responsible for measuring parameters such as voltage, current and temperature of the battery, and also has functions such as equalization. When the CMU measures these data, it transmits the data to the BMU through the aforementioned battery "neural network".

BMU: Battery management Unit .

Responsible for evaluating the data transmitted by the CMU. If the data is abnormal, it will protect the battery, issue a request to reduce the current, or cut off the charging and discharging path to prevent the battery from exceeding the permitted use conditions. At the same time, it also manages the power and temperature of the battery. According to the previously designed control strategy, judge the parameters and states that need to be warned, and send the warning to the vehicle controller, and finally convey it to the driver.

Process flow

Battery PACK is the core energy source of new energy vehicles, providing driving power for the entire vehicle. As the core component of new energy vehicles, its quality directly determines the performance of the vehicle. Lithium battery manufacturing equipment is generally divided into three types: front-end equipment, middle-end equipment, and back-end equipment. The accuracy and automation level of the equipment will directly affect the production efficiency and consistency of the product.

Although the types of batteries and modules are different, the composition and process flow of PACK are roughly the same (not all manufacturers have the same process flow)

PACK assembly process

Mainly divided into assembly process, air tightness testing process, software writing process, electrical performance testing process, etc.

Production line introduction

There are many flexible lines and press-fitting and tightening in the PACK assembly process. It is more difficult to automate and the input-output ratio is not high. Therefore, the automation degree of the rear-end equipment will be lower than that of the front-end and middle-end equipment, but it is compatible with cylindrical and square shells. , and soft pack three kinds of PACK battery pack assembly.

Stations that may require automation:

-The lower housing is automatically on the line

-Module automatically goes online into the housing

-Module is fixed and screwed

-The upper cover is threaded and tightened

- Automatically apply A/B thermal paste (depending on the process)

- Automatic sealant application (depending on the process)

- Finished product off the assembly line

With the gradual maturity of the development of the power battery industry, the battery PACK modular technology will become more and more mature. The development of battery PACK technology involves multi-disciplinary and multi-field knowledge, and requires interdisciplinary technology integration. All in all, if car companies want to finally produce PACK products on a large scale that fully meet the requirements of new energy vehicles in terms of life, stability, reliability, and safety, they still need a lot of engineering practice and test verification, as well as continuous optimization and upgrading of products process.

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