Today, I will share the key points of the lithium battery pack PACK manufacturing process.
Cell distribution group
The first step is the sorting and matching of cells. The parameters set on the automatic sorting machine should be: (cylindrical cells as an example, ternary system battery and lithium iron phosphate battery)
The voltage difference is 5mV (if the number of cells is large and the consistency requirements are strict, you can choose to set 3mV as the first gear);
The internal resistance difference is 3mΩ (1-2mΩ can be set if the consistency requirements are strict).
The difference in capacity cannot be screened on the automatic sorting machine, and it needs to be divided into the aging cabinet for capacity allocation. Before leaving the factory, the cells will be sub-packaged and shipped according to the voltage, capacity, and internal resistance. When the cells arrive, the IQC of the PACK department needs to conduct a random inspection, and the capacity difference is recommended to be within 1%.
Lithium battery pack cells are equipped with fixtures and automatic spot welding machines.
When installing the cell fixtures, be sure to assemble the cells in the order of the positive and negative poles in the PE engineer’s SOP. Reversing the order will cause the cells to short-circuit. After setting the automatic welding machine program, put the fixture cell in and start automatic spot welding.
After the automatic spot welding is completed, the quality of the battery pack needs to be checked for automatic spot welding, and repair welding is required at the leaking point.
Lithium battery pack welding PCM/BMS
In this step, employees must wear an electrostatic wristband to avoid electrostatic damage to the PCM/BMS.
There are different steps according to different battery pack designs. If it is designed to be spot welded to the battery pack by PCM, soldering is not required, and the quality also needs to be spot welded to the battery pack from the PCM.
If the PCM/BMS needs solder, the PACK of the connecting screws, the solder joints, and the screw connection points also need to be inspected. guaranteed quality. The voltage collection line needs to be sequentially B-, B1… to B+; or unplug the voltage collection line and then weld it. After the welding is completed, check the collection line and confirm that it is correct before connecting to the BMS.
Semi-finished insulation
Necessarily fix and insulate the voltage collection lines, wires, and positive and negative output lines. The usual accessories are high-temperature adhesive tape, highland barley paper, epoxy board, cable ties, etc. It is necessary to be aware of safety, and not superimpose pressure on the voltage collection line or output wire of the battery pack, which may easily lead to extrusion damage and short circuit.
Semi-finished product testing
After adding BMS to the battery pack, a semi-finished product test can be carried out. The routine tests include a simple charge and discharge test, an internal resistance test of the whole group, a capacity test of the whole group, an overcharge test of the whole group, an over-discharge test of the whole group, a short circuit test, and an overcurrent test. If there are special requirements, high-temperature and low-temperature tests, acupuncture tests, drop tests, salt spray tests, etc., a special lithium battery pack test, which is destructive, is recommended.
It is necessary to pay attention to the bearing capacity of the battery pack, such as whether the BMS can withstand high voltage during the overcharge test of the whole group; whether the BMS can withstand instantaneous high voltage and high current during the short circuit test; whether the BMS can withstand pulse current during the overcurrent test, etc.
Battery pack PACK packaging
This step also needs to look at the design. However, before packaging, the signal acquisition line must be well insulated, and the positive and negative electrodes of the battery pack must be insulated.
The battery pack in PVC packaging is heat shrinkable. Ultrasound sealed battery pack, on the ultrasound machine. Battery pack with the metal outer case for outer case assembly. During this process, care should be taken to handle the battery pack with care to avoid a collision, squeezing, etc. The wires should be well insulated to avoid short circuits.
the whole set of tests
The parameters of the whole group of testers are set, and the whole group of testers on the battery pack is tested.
Main test items: shipping voltage, internal resistance, simple charge, and discharge.
Alternative test items: overcurrent, short circuit.
Packing and shipping
Pack the box according to the size of the open mold foam. Do not place it randomly. When transporting the battery pack, you are most afraid of empty internal packaging. Be sure to ensure that there is enough foam inside for buffering to avoid damage during transportation. Large battery pack PACK, for safety reasons, it is necessary to arrange for shipment in wooden boxes.