How do we design and assemble Lithium Ion Battery Packs?

These are the important steps we follow:

Preliminary planning and preparation:

Demand analysis: Before project starts, we always have a deep communication with our customers and confirm the application of the battery pack, such as whether it is used in general electronic products or electric vehicles, energy storage equipment, etc.. It will help us determine the required voltage, capacity, power and other parameters, as well as the temperature, humidity, vibration conditions of the working environment.

Cell selection: Carefully select suitable lithium-ion cells based on the results of demand analysis. Common type cells include cylindrical (such as 18650, 21700, etc.) and prismatic Lithium Polymer cells. It is necessary to consider the performance indicators of the cell such as capacity, voltage, internal resistance, charge and discharge rate, safety, cycle life and other market factors such as cost and availability.

Design plan formulation: Design the structure and connection method of the battery pack according to the cell selection and demand, including the series and parallel combination of the cell, the external dimensions of the battery pack, the fixing method, etc. At the same time, determine the protection circuit design of the battery pack, such as overcharge protection, over-discharge protection, overcurrent protection, short-circuit protection and other functions.

Battery cell processing and testing:

Battery cell capacity division: Perform capacity division tests on the battery cells to group battery cells with similar parameters such as capacity, internal resistance, and voltage to ensure the consistency of the battery pack.

Battery cell testing: Test the voltage, internal resistance and other parameters of the battery cells, and remove unqualified battery cells. At the same time, we will also check whether the appearance of the battery cells is damaged or deformed.

Battery pack assembly:

Welding connection: According to the design plan, the battery cells are connected in series and parallel by welding. We will ensure that the solder joints are firm, without false solder joints, short circuits and other problems. 

Install PCB: The protection board can monitor and protect the charging and discharging process of the battery pack to prevent overcharging, over-discharging, overcurrent, short circuit and other situations.

Insulation treatment: Insulate the battery pack between the cells, between the cells and the shell, and the connecting wires, and use insulating tape, barley paper and other insulating materials to prevent safety problems such as short circuits.

Packaging and fixing: Put the assembled battery pack into the shell and fix it. The shell can protect the battery pack, prevent external damage, and facilitate installation and use. For some battery packs with high heat dissipation requirements, it is also necessary to design a heat dissipation structure on the shell.

Testing and verification:

Appearance inspection: Check whether the appearance of the battery pack is intact, whether the shell has deformation, damage and other problems, and whether the connecting wires are firmly connected.

Electrical performance test: Test the electrical performance parameters of the battery pack, such as voltage, capacity, internal resistance, charge and discharge rate, to verify whether the battery pack meets the design requirements.

Protection function test: Simulate abnormal conditions such as overcharging, over-discharging, overcurrent, short circuit, etc., and test whether the protection function of the protection board works normally.

Cycle life test: Perform multiple charge and discharge cycle tests on the battery pack to verify whether the cycle life of the battery pack meets the requirements.

Quality inspection and packaging:

Quality inspection: Conduct a comprehensive quality inspection on the battery packs that have passed the test, including appearance, electrical performance, protection functions, etc., to ensure that the quality of the battery pack meets the standards.

Packaging: Pack the battery packs that have passed the quality inspection. The packaging must have good protective performance to prevent the battery pack from being damaged during transportation and storage. At the same time, mark the battery pack model, specifications, parameters, production date and other information on the packaging.