The manufacturing process of energy storage lithium battery pack (PACK) involves multiple steps, from the selection of raw materials to the assembly and testing of the final product. Each step requires strict quality control to ensure the safety and reliability of the product.
1, Cell sorting and grouping:
Testing and screening: Strictly test the purchased battery cells and group them based on parameters such as voltage, internal resistance, and capacity. For example, the range of voltage difference and internal resistance difference control (data may vary depending on the battery cell and customer requirements).
Capacity allocation: Capacity difference cannot be screened on the automatic sorting machine and needs to be allocated through a capacity aging cabinet. Upon arrival, the IQC (Incoming Quality Control) of the PACK department needs to conduct spot checks. The recommended control range for capacity difference is to ensure the consistency of the battery cells, which is crucial for the performance and lifespan of subsequent lithium battery packs.
2, Assembly and welding of battery cells:
Assemble battery cells in a clean and dry environment to avoid damage from dust, moisture, and other factors.
Cell assembly fixture: When installing the cells into the fixture according to the design requirements, it is necessary to strictly follow the positive and negative electrode sequence of the cells in the SOP (Standard Operating Procedure) formulated by the PE engineer for assembly, otherwise serious problems such as cell short circuits may occur.
According to the design plan, fix the sorted and grouped battery cells with fixtures or trays to ensure tight and stable connections between the cells. Adopt reasonable insulation measures, such as using insulation gaskets, insulation tape, etc., to prevent short circuits between battery cells.
Welding operation: After setting up the automatic welding machine program, perform automatic spot welding. After spot welding is completed, quality personnel need to conduct a comprehensive inspection of the welding points to see if there are any omissions, explosions, or other issues. If there are any, they need to be repaired in a timely manner.
3, Box assembly:
Installation of box panel assembly, BMS size board, connectors, and hanging ears
Installation of B+B-wire harness
Apply insulation materials
4, BMS assembly and debugging:
1. BMS assembly
Electrostatic protection: Employees must wear an electrostatic wristband during operation, as static electricity may cause damage to the PCM/BMS and affect its normal function.
Connect the BMS to the battery cells, ensuring that the connection lines are correct and secure. Pay attention to the installation position of BMS, which should be convenient for heat dissipation and maintenance, while avoiding external impact and interference.
Organize and fix the connection wires of BMS, and use cable trays, zip ties, and other methods for wiring to make the lines neat and orderly, reducing the risk of line failures.
Collection line welding: If the BMS is designed to spot weld the battery pack, there is no need for welding. Quality personnel need to inspect the spot welding points between the BMS and the battery pack; If BMS requires soldering to connect screws, spot checks should also be conducted on the solder joints and screw connection points. For voltage acquisition lines, they need to be connected in sequence (such as B -, B1... to B+), or welded after unplugging the voltage acquisition line socket. After welding, the acquisition socket should be checked and confirmed to be correct before connecting to the BMS.
2. BMS debugging
Set and debug the parameters of the installed BMS, and set reasonable charging and discharging protection thresholds, balancing parameters, communication protocols, etc. based on the specifications and application requirements of the energy storage battery pack. For example, set the overcharge voltage protection value to 1.1 times the rated voltage of the battery cell, and the overdischarge voltage protection value to 0.9 times the rated voltage of the battery cell.
Test and verify the functionality of BMS by simulating the charging and discharging process. Check the accuracy of battery monitoring, balance effect, and protection function of BMS to ensure that the energy storage battery pack can be effectively managed and protected during operation.
5, Semi finished insulation:
Fixing and protection: Necessary fixing and insulation treatment should be carried out on voltage acquisition lines, wires, positive and negative output lines, etc. Common auxiliary materials include high-temperature adhesive tape, barley paper, epoxy board, zip ties, etc. During the operation, it is necessary to ensure the reliability of insulation measures and avoid mutual interference and short circuit risks between lines.
Avoid squeezing: Safety awareness is required, and do not stack or compress the voltage collection line or output wire of the battery pack to avoid damaging the circuit due to squeezing and causing a short circuit.
6, Semi finished product testing:
Routine testing: After adding BMS to the battery pack, a semi-finished product test is conducted. Routine testing items include simple charge and discharge testing, whole group internal resistance testing, whole group capacity testing, whole group overcharge testing, whole group overdischarge testing, short circuit testing, overcurrent testing, etc.
Special testing: According to the special requirements of the product, high temperature, low temperature, needle puncture, drop, salt spray and other tests may also be required, but these special tests are destructive and it is generally recommended to conduct random inspections. During testing, attention should be paid to the battery pack's ability to withstand high voltage, such as whether the BMS can withstand high voltage during overcharge testing, whether the BMS can withstand instantaneous high voltage and current during short-circuit testing, and whether the BMS can withstand pulse current during overcurrent testing.
7, Test validation:
Conduct comprehensive testing on the packaged energy storage battery pack, including capacity testing, internal resistance testing, cycle life testing, safety performance testing, etc. For example, conducting charge and discharge cycle tests to verify the capacity retention rate and cycle life of the battery pack; Conduct short-circuit testing, overcharge and over discharge testing, needle puncture testing, etc. to ensure the safety performance of the battery pack under various extreme conditions.
Analyze and evaluate the test results, rework or scrap products that do not meet the requirements, and ensure the reliable quality of the energy storage battery pack that leaves the factory.
8, Packaging:
Insulation treatment: Before packaging, the signal acquisition line and the positive and negative poles of the battery pack must be insulated to ensure that the battery pack will not cause short circuits or other faults due to contact issues during the packaging process.
Packaging method: Choose different packaging methods according to design requirements. For example, PVC packaged battery packs require a heat shrink machine, ultrasonic sealed battery packs require an ultrasonic machine, and battery packs with metal outer boxes require outer box assembly. During the packaging process, attention should be paid to handling with care, avoiding collisions, squeezing, and other situations to prevent damage to the battery pack.