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From the cell to the battery pack, any oversight at every stage can potentially sow the seeds of trouble.
time：2026-07-27
Power battery PACK (battery PACK integration) is the core link between cell and the whole vehicle, with high technical complexity and strict quality requirements. In the actual production process, many seemingly conventional operation details often become key variables that affect the performance, service life and even safety of battery pack. This article sorts out the five core issues that must be highly vigilant in the PACK process and provides practitioners with a practical risk prevention and control guide.
I. Cell consistency of incoming materials: chain reaction of improper allocation
cell is a "cell" of battery pack, and its consistency directly determines the maximum performance of the whole package. If the incoming inspection is not strictly controlled, all subsequent processes will get twice the result with half the effort.
Capacity and internal resistance deviation is the primary filter indicator. Cell with a capacity difference of more than 1.5% and a internal resistance difference of more than 3% are not allowed to be allocated. Otherwise, "short board effect" will easily occur during the cycle-cell with low capacity will reach the cut-off voltage first, as a result, the available capacity of the whole package will shrink, and local overcharge and overdischarge will be caused for a long time.
Voltage and self-discharge rate the same cannot be ignored. The difference of incoming voltage should be controlled within 50mV, and the difference of self-discharge rate should be controlled within 0.5%/month. Ignore these two parameters, battery pack after standing for several weeksSignificant pressure difference may occur, and the BMS equalization system is overwhelmed.
II. Welding process control: life and death line of connection quality
welding is one of the processes with the highest failure rate in PACK. The quality of solder joint directly determines the electrical reliability and safety of the whole package.
Laser welding parameters accurate matching of material characteristics is required. Aluminum Case cell of the electrode lug welding, the power is too high and easy to burn through, the power is too low, the penetration is insufficient; Copper bar and aluminum row of the heterogeneous metal connection, must use ultrasonic welding or nickel plating transition, to prevent electrochemical corrosion. After welding, 100% tension test and X-Ray test are required, and virtual welding, pores and cracks are all reworked.
Welding sequence and heat effect equally particular. When welding high-current bus bar, heat conduction may damage nearby's BMS sampling line or temperature sensor. Reasonable fixture and welding path planning is the key to avoid thermal damage.
III. Thermal Management Design: millimeter class game of temperature difference control
Liquid cold plate flow channel layout uniformity and pressure drop should be considered. Too narrow flow channel leads to high coolant flow rate and increased pump power; If the flow channel is too wide, the heat exchange efficiency decreases. Excellent runner design can control the maximum temperature difference of the whole package within 3℃, while improper design may make the temperature difference between the edge cell and the center cell exceed 8℃, and the cycle life gap can reach more than 30%.
Thermal interface material (TIM) the selection and coating process are often underestimated. The thickness uniformity, compression ratio and thermal conductivity attenuation after long-term aging of thermal conductive pad should be strictly controlled in design and incoming inspection. The glue breaking and bubbles of the gluing track are the key objects of production line inspection.
IV. BMS sampling accuracy: the foundation of software security
BMS is battery pack "nervous system", and its sampling accuracy directly determines the effectiveness of protection strategies.
Voltage sampling the precision must reach ± 5mV, and the sampling line must adopt twisted pair shielded wire, which is far away from the arrangement of high-current busbar to prevent electricity.Magnetic interference causes sampling drift. The sampling point must be close to the cell pole or busbar, while the non-module shell, otherwise the temperature lag and contact resistance will introduce systematic errors.
Temperature sampling the distribution strategy is also critical. At least one sampling point shall be arranged for each cell and shall be located at the center of the cell large surface-where the temperature can best reflect the true state of the cell. Redundant sampling is required for module edge, inlet and outlet, etc. to form three-dimensional temperature field monitoring.
V. Insulation and sealing: double insurance for high pressure safety
battery pack high-voltage insulation and protective seal are the last line of defense to ensure the safety of users. Any omission may lead to serious consequences.
Insulation Resistance the three nodes shall be tested separately after the whole package is assembled, before liquid injection and before offline to ensure that there is no insulation damage in each stage. The test voltage should cover 1.5 times of the rated voltage of the system, and the insulation resistance value should be greater than 500 Ω/V. The insulation retest after damp-heat test and vibration test is even a verification link that cannot be omitted.
Seal design attention should be paid to seal selection, gluing process and fastening torque. The sealing ring material should take into account electrolyte corrosion resistance, high and low temperature elasticity and long-term compression permanent deformation rate; The width, height and glue breaking point position of the gluing track should conform to the process specifications; torque-angle method shall be adopted for Bolt fastening to ensure uniform distribution of pressure on the sealing surface. Required for air tightness testAfter normal temperature and high temperature aging, the leakage rate exceeds the standard and must be retroactively reworked.
PACK Battery there is no shortcut, only the ultimate pursuit of every detail. Cell consistency is the foundation, welding quality is the link, thermal management is the life guarantee, BMS accuracy is the safety bottom line, insulation seal is the last line of defense. With the rapid development of new energy vehicle and energy storage industry, the technical depth and quality control capability of PACK link are becoming the core competitiveness for enterprises to cross the cycle and win trust. After all, the value of a piece of battery pack lies not only in how much energy it can store, but also in whether it can release these energy safely, stably and reliably throughout its life cycle.
Contact us
Dongguan Juneng New Energy Technology Co., Ltd.
137 5142 6524（Miss Gao）
susiegao@power-ing.com
Xinghuiyuan High tech Industrial Park, Dalang Town, Dongguan City, Guangdong Province
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