In the Previous article, we saw the first three parts of the Battery Pack Manufacturing process: Electrode Manufacturing, Cell Assembly, Cell Finishing. Article Link
In this article, we will look at the Module Production part. The Remaining two parts Pack Production and Vehicle Integration will follow in the next articles. :
- Module Production (In this Article)
- Pack Production
- Vehicle Integration
1. Module Production
There are 7 Steps in the Module Production Part: (I have used mostly Prismatic Cells Module Production, will add other cell Types as separate or addition to this article)
Step 1: Incoming Cells Inspection:
- Some OEM Vehicle Manufacturers and Battery Manufacturers Purchase the Cells from Another Supplier
- In this case the First Step for the cells will be over checks when they are delivered to the factory.
- Cells undergo thorough Incoming Checks
- OCV – Open Circuit VoltageACIR – Alternating Current Internal Resistance
- EIS – Electrical Impedance Spectroscopy
- Capacity Analysis
- Based on the above Checks the Cells are Sorted by Binning into Categories
- Cells surfaces are cleaned for Eg by Laser Cleaning/Ablation.
- Surfaces might be painted for Protection
- Adhesive Tapes are applied to one surface or Glue is added to one surface depending on the process.
- Depending on above medium there might be a need for Extracting Vapours.
- The cells are then stacked.
Cell is Plasma or Laser Cleaned
Adhesive Tape is stuck to one side of the Cell
Step 3: Stacked Cells Tightening/loading with End Plates:
- End Plates or Pressure Plates are welded and cleaned with Plasma.
- They are placed at opposite ends
- Stacked Cells are placed in the middle
- They are preloaded or Tightened by Force of Clamping device or Module Body.
- Supporting Insulation Plates are added.
- The whole System can be put inside a Module Case.
Step 4: Connecting the Cells inside the Module
- Current Collectors or Contact Tabs are electrically wired together
- The Contacts are done by Welding (Ultrasonic, Laser, Resistance Welding) or Screwing
- Welding methods for electrical connections in battery systems by Harald Larsson, Alec Chamberlain, Sally Walin, Samir Schouri, Louise Nilsson, Elin Myrsell, Daniel Vasquez. Link
- Conductivity is measured by resistance Measurements
- Mechanical strength can be assessed with a Pull Test
- Optical Inspection is used to measure Welding seams
Step 5: Mounting of the BMS Cell Sensing Circuit (CSC)
- BMS CSC is positioned on the Top of the Battery or Unit
- The Module at this point may undergo another round of Plasma Cleaning
Dotoli, M.; Rocca, R.; Giuliano, M.; Nicol, G.; Parussa, F.; Baricco, M.; Ferrari, A.M.; Nervi, C.; Sgroi, M.F. A Review of Mechanical and Chemical Sensors for Automotive Li-Ion Battery Systems. Sensors 2022, 22, 1763. https://doi.org/10.3390/s22051763
Step 6: Cell Stack is Loaded into Module Housing
The module housing design can include the thermal management system or more often the modules are mounted onto larger cooling plates. Larger cooling plates can help reduce the number of parts and pack complexity. It is important that the connection between the cells and the cooling plates is electrically isolated and thermal connected. If Thermal Paste is used to improve this connection then a Hardening Process takes Place after the Module is put on the Thermal Paste.
This shows the assembly of the modules onto an “elongated X” shaped thermal interface material.
One of the shapes that can give the best overall coverage between cooling plate and battery module.
Step 7: End of Line Testing and Quality Control of the Module
The Modules then will undergo Quality Control where depending on the manufacturer quality criteria various parameters are checked. Insulation, Optical Check, Slave BMS testing, Leakage test for Module Housing, Connectivity Test, Connectors, Charge and Discharge Test, SOC, Thermal etc.
Following Article will contain the remaining two parts: Pack Production and Vehicle Integration
YouTube Video Links:
- BMW i3 https://www.youtube.com/watch?v=iiJsKza5CF4
- 2022 BMW Battery – Car Factory Production (BMW Plant Leipzig): https://www.youtube.com/watch?v=LZIZsl-7fT4
- Kuka Fully Automated Battery Module Production: https://www.youtube.com/watch?v=JESmMRO5CGYMG
- Electric Car Batteries: Battery Pack assembly and Test https://www.youtube.com/watch?v=knmqqB35yAQ
Major thanks to this article as it forms base of my article. Battery Module and Pack Assembly Process, RWTH Aachen University.