Lithium battery PACK knowledge sharing

Since its inception, lithium batteries have been favored by 3C digital, power tools, and other industries due to their high energy density, high voltage, environmental protection, long life, and fast charging, and their contribution to the new energy automobile industry is particularly prominent. As the world’s energy crisis and environmental protection issues become increasingly prominent, the lithium battery industry, which provides the power source of new energy vehicles, has huge market potential and is an important part of national strategic development.

Lithium battery pack basic introduction

Classification and composition of Lithium battery pack

What is Lithium 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, and generally provides a voltage between 3v-4v;

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

Lithium 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 Lithium battery pack

As the core component of PACK, batteries are currently divided into three main categories based on the shape of batteries: prismatic cell, cylinder cell, and pouch cell. (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 internal resistance of the connection point, laser welding is currently the first choice of many battery manufacturers.

Composition of Lithium battery pack

It mainly includes battery modules, mechanism systems, electrical systems, thermal management systems, and BMS.

Battery module

If the Lithium 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.

Mechanism system

It is mainly composed of a Lithium battery PACK cover, tray, various metal brackets, end plates, and bolts, which can be regarded as the “skeleton” of battery PACK, which can support, and resist mechanical shock, mechanical vibration, and environmental protection (waterproof and waterproof) dust.

Electrical system

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”.

Process flow

Lithium 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 generally the same (not all manufacturers have the same process flow), as shown in the figure below for reference.

PACK assembly process

It is mainly divided into the 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 Lithium battery pack assembly.

Automatic workstations that may be required: – Automatic loading of the lower housing – Automatic loading of the module into the housing – Fixing and tightening of the module – Threading and tightening of the upper cover – Automatic coating of A/B thermal adhesive (depending on the process) – Automatic coating Sealant (depending on the process) – finished product off the assembly line

In addition, some will propose that automatic methods are required for bronze installation, screw tightening, air tightness testing, and EOL testing, which are relatively rare and difficult to guarantee stability.

There are two main types of operation for the mass production equipment of the back-end PACK line:

Assembly trolley

In the past, it was mainly used in car factories, and now battery factories are slowly promoting this mode.

Conveyor line + tray mode

Drum Line/Roller Friction Line/Multiplier Chain Conveyor Line

Summarize

The above is the basic knowledge explanation of lithium battery pack.

With the gradual maturity of the development of the power battery industry, the lithium battery PACK modular technology will become more and more mature.

The development of Lithium battery PACK technology involves multi-disciplinary and multi-field knowledge and requires interdisciplinary technology integration. All in all, if car companies want to finally Lithium 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.