Refinement of the raw materials, through cell assembly and finally to battery pack the manufacturing process is complex and requires a broad range of skills.
Cell Pilot Line
A flexible line used to make tens or hundreds of cells and to prove the technology can be made on a production line. This also allows initial testing of larger cell quantities and with closer cell to cell tolerance.
Cell Manufacturing
A huge subject and hence a dedicated area to look at the stages, chemistry, costs and future direction.
Cell Manufacturing Process
In order to engineer a battery pack it is important to understand the fundamental building blocks, including the battery cell manufacturing process. This will allow you to understand some of the limitations of the cells and differences between batches of cells. Or at least understand where these may arise.
Cell Testing
When assembling cells into a module, pack or directly into a product there are a number of tests that need to be done to ensure quality control.
What level of cell matching do you do prior to assembling a battery pack? Assuming the Page_DownPage_DownPage_Downbattery pack will be balanced the first time it is charged and in use. Also, assuming the cells are assembled in series.
- none, force the cell supplier to deliver cells matched to within +/-0.02V
- none, gross balance the pack during first charge once built
- preselect and group cells prior to build
- pre-charge/discharge all in-coming cells to a set voltage/SOC
- average-balance cells in parallel group prior to building in series
- average top-balance cells in parallel group prior to building in series
Within the stages of battery manufacture it is important to understand Clean and Dry Room requirements.
Defects
Cell defects can result in open-circuit and short-circuit failures.
Using CT Scanning to Detect Battery Defects
Battery defects are a major scourge on the industry. In fact, battery defects have been deemed responsible for major billion-dollar electric vehicle recalls.
CT scanning cells is a way of understanding manufacturing quality issues.
Module Manufacture
There are 7 Steps in the Module Production Process:
- Incoming Cells Inspection
- Preassembly
- Stacked Cells Tightening/loading with End Plates
- Connecting the Cells inside the Module – covered in more depth under Welding and Cell Joining Techniques
- Mounting of the BMS Cell Sensing Circuit (CSC)
- Cell Stack is Loaded into Module Housing
- End of Line Testing and Quality Control of the Module
Pack Manufacture
Battery Pack Assembly Bill of Process
A generic battery pack assembly bill of process that lays out the significant steps and challenges.
Battery Assembly Times: A look at battery assembly times based on available reports and data.
Essential Processes Behind Reliable Lithium Battery Packs
Before a lithium battery pack is ever assembled, a critical process quietly takes place: ensuring that every single cell inside the pack—whether 18650, 21700, or other steel‑shell cylindrical formats—can perform consistently and safely. In modern li-ion battery manufacturing, cell testing and matching are not optional steps—they form the foundation of long-term reliability.
Defects
The battery pack has a large number of components and interfaces that are critical and hence important to understand those pack defects, how to detect and correct.
The application of thermal interface materials is also an important consideration in manufacturing as this pattern can result in non-uniform or even voids in the TIM.
Quality Control
At all stages of battery manufacturing we need to have Quality Control (QC). As battery technology continues to evolve, so too must our strategies for ensuring their safety and reliability.
See also
End-of-Line (EOL) Cell Production Testing, Cell Manufacturing Strategy