Key takeaways
At 6,000 cells an hour, a line handles one cell every 0.6 seconds. In that time the cell has to be picked up, cleaned, insulated, identified, tested and placed into a group with cells that behave like it. Do that for a full shift and roughly 48,000 cells pass through, each one with its own test record.
Cybernetik’s cell handling line for battery pack assembly unloads cells from cartons, plasma cleans their terminals, applies and checks insulation paper, reads barcodes, measures open circuit voltage and AC internal resistance, and uses SCARA robots to sort cells onto parallel conveyors by test result before forming modules. It handles up to 6,000 cells per hour across cylindrical, prismatic, pouch and blade formats. This article walks through what happens at each station and why the sequence matters.
What 6,000 Cells per Hour Means in Practice
A cells-per-hour figure only becomes useful once it is turned into packs. As an illustration, using a common 21700 cylindrical cell of roughly 18 watt-hours:
| Pack example | Approximate cells | Packs per hour | Packs per 8 hour shift |
|---|---|---|---|
| 2 kWh two-wheeler pack | About 110 | About 54 | About 430 |
| 3 kWh two-wheeler pack | About 170 | About 36 | About 290 |
| 60 kWh car pack | About 3,300 | Under 2 | About 14 |
These are rough figures. Actual pack counts depend on the cell chosen, the pack configuration, how many packs need rework and how well the stations after cell handling keep pace. The point they show is that cell handling capacity suits two-wheeler and three-wheeler production well, where packs are small and numerous, and for larger packs the same line feeds fewer, bigger assemblies.
Why Sort Cells at All
No two cells are identical, even from the same batch. Small differences in capacity and internal resistance mean that, inside a pack, some cells work harder and age faster than others. Over time the weakest cell decides the usable capacity of the whole pack.
Testing every cell and grouping cells with similar readings reduces that spread before the pack is built, which is far easier than managing it afterward. The reasoning behind matching, and what happens when it is skipped, is covered in the article on cell sorting and grading.
The Line, Station by Station
| # | Station | What happens there |
|---|---|---|
| 1 | Carton unloading | Cells are taken out of supplier cartons, with multiple cartons and cell sizes handled |
| 2 | Pick and place | SCARA robots move cells, with a vision system checking cell count; rapid tool change suits different cell sizes |
| 3 | Plasma cleaning | Terminals are cleaned on the fly to improve weldability |
| 4 | Insulation paper and check | Paper covers the positive terminal to prevent shorts during welding, checked by AI-based vision |
| 5 | Barcode reading | Several cells are read at once on a rotary station, starting the cell-to-module link |
| 6 | Cell testing | Open circuit voltage and AC internal resistance are measured for every cell |
| 7 | Cell sorting | SCARA robots place cells onto parallel conveyors based on their test results, with a rotary flipper inverting alternate rows |
| 8 | Module formation | Robots place sorted cells into holders, with vision checking polarity and adjustable gripper pitch |
The order is deliberate. Cleaning comes before testing and welding, insulation is applied before cells are handled into modules, and identity is captured before measurement so every reading is tied to the right cell. Each station prepares the cell for the next one.
Unloading and Pick and Place
Cells arrive packed in cartons, often in trays, and moving them by hand is slow and risks damage to the casing or terminals. The carton unloading station handles multiple cartons and cells of different sizes and types, so the line is not tied to one supplier’s packaging.
SCARA robots then pick cells and place them onto the line. A vision system checks the cell count, which catches missing or extra cells early, and rapid tool change lets the robots switch between cell sizes without a long stop.
Plasma Cleaning on the Fly
Cell terminals carry thin films of oil, oxides and handling residue that are invisible but affect how well a weld forms. A weld made through a contaminated surface may pass inspection and still have higher resistance or weaker strength than it should.
The line cleans terminals with plasma as cells move, rather than stopping them, which keeps the cycle time intact. How plasma cleaning works and why it improves joining is explained in the article on plasma cleaning in battery cell preparation.
Insulation Paper and Its Check
On cylindrical cells, the positive terminal sits very close to the casing, which is connected to the negative. During welding and module assembly, a stray contact across that gap can short the cell. Insulation paper applied around the positive terminal prevents it.
A missing or misplaced insulation ring is easy to overlook and serious if it reaches the module. The line checks each application with AI-based vision, so a faulty cell is caught at this station rather than discovered after welding.
Barcode Reading and the Parent-Child Link
Every cell carries an identity, and the line reads it before testing. A rotary station places cells vertically below the reader, and scanners read several cells at once so identification does not slow the line.
That reading is the start of the parent-child relationship: each cell is linked to the module it goes into, and later each module to its pack. Barcodes are read at multiple stages, so the link survives the whole assembly. If a pack ever comes back from the field, its build history can be traced to the individual cells inside it.
Testing Every Cell
Two measurements are taken on every cell. Open circuit voltage shows the cell’s state of charge and can reveal cells that have self-discharged abnormally in storage. AC internal resistance shows how readily the cell delivers current, and a cell with unusually high resistance will heat more and age faster in a pack.
Data capture uses Python and MATLAB, so readings are recorded against each cell’s identity rather than displayed and lost. What these measurements reveal and how they are interpreted is covered in the guide to OCV, IR and ACIR battery cell testing.
Sorting by Test Result
This is the station that gives the line its name. After testing, SCARA robots place each cell onto one of several parallel conveyors according to its readings. Cells with similar results travel together, so the modules built from each lane contain cells that are closely matched.
Parallel conveyors also keep the line moving. A single output lane would force cells to wait for each other; several lanes let the robots place each cell where it belongs without holding up the next. A rotary flipper then inverts cells in alternate rows, which sets up the alternating orientation many module designs use to connect cells in series.
How many groups are used, and where the boundaries between them sit, should follow the pack design and the cell supplier’s spread rather than a fixed machine setting. Tight groups give better matching but need more lanes and leave more cells waiting for partners.
What Happens to Cells That Do Not Fit
Every sorting line has to decide what to do with cells that fall outside the acceptable range. Some will have abnormal voltage after long storage, some will show high resistance, and a few will be damaged in transit. Planning for them is part of designing the line, not an afterthought.
The practical questions are where rejected cells go, how they are kept physically separate from good stock, and how their records are marked so they cannot be mixed back in later. Cells that are slightly outside the main groups may still be usable in a different product or a later batch, which is another reason grouping limits should be set by the pack design team rather than left as a machine default.
Where Time Is Won or Lost at 0.6 Seconds
At this pace, small delays add up quickly. A station that takes a tenth of a second longer than planned removes hundreds of cells from every hour of output. That is why the line does several things at once rather than in sequence.
The station that sets the pace in practice is usually the slowest one at that moment, which can shift with cell format. Measuring cycle time at each station during commissioning, with the actual cells the plant will run, shows where the real limit sits.
Cells Change While They Wait
Cells keep slowly discharging in storage, and warm storage speeds that up. A cell tested on arrival and stored for weeks may read differently when it reaches the line. Testing at the line, immediately before sorting and module formation, means grouping reflects the cell as it is going into the pack rather than as it was when it was received. Plants that store cells for long periods also benefit from rotating stock so older cells are used first.
Forming Modules
Sorted cells are placed into holders by SCARA robots. A vision system checks polarity before placement, since a reversed cell in a series string is one of the more damaging faults a module can carry, and gripper pitch can be changed to suit different cell sizes and types.
From here the module moves to welding. The line integrates both laser and resistance welding, and the choice between joining methods is covered in the comparison of laser welding and wire bonding for cell interconnects.
“Battery production lines must adapt as cell formats and pack designs evolve. Flexible robotic handling, adjustable tooling, and configurable sorting groups help manufacturers accommodate changing requirements without rebuilding the entire process.”
See it in action
Why Robots Rather Than People
Manual sorting is possible at low volumes, and many pilot lines start that way. It breaks down as output rises. Operators placing cells by hand into groups based on a screen reading make occasional mistakes, and at thousands of cells a shift, occasional becomes several per hour. Handling also transfers oils from skin to terminals, which works against the cleaning step.
Robots place each cell exactly where its reading says it belongs, every time, and the record of where it went is created automatically. People remain essential for setting limits, watching trends and handling exceptions, which is where their judgment adds the most.
One Line, Several Cell Formats
Battery manufacturers rarely stay with one cell for long. Suppliers change, new pack designs arrive and different products need different chemistries and sizes.
The line handles cylindrical cells including 18650, 21700 and 32140, with larger cylindrical diameters of 32, 33, 35, 40, 42 and 46 mm listed for the EV assembly line, alongside prismatic, pouch and blade formats. Rapid tool change on the pick and place robots and adjustable gripper pitch at module formation are what make switching practical. A line built around one format can be cheaper at the start and expensive the first time the cell changes.
What to Ask When Evaluating a Sorting Line
| Question to ask any supplier | Why it matters |
|---|---|
| What rate is quoted, and for which cell size? | Throughput depends on format, so a headline figure needs its conditions |
| Which measurements are taken on every cell? | Sampling misses the outliers that limit a pack |
| How are sorting groups defined, and who sets the limits? | Grouping rules should follow your pack design, not the machine |
| How is polarity confirmed before welding? | A reversed cell is a serious fault that is hard to catch later |
| How long does a format change take? | Lines running several products lose output at every changeover |
| Is each cell linked to its module and pack? | Traceability decides how quickly a field issue can be investigated |
| Can the line be tested at the factory before shipping? | Problems found at the supplier cost far less than on your floor |
These questions apply to any supplier, including Cybernetik. A headline rate is a starting point, and the answers to these questions decide whether that rate holds up on your floor with your cells.
Beyond Cell Handling
Cell sorting is the first part of a longer process. After module formation come welding, inspection, module assembly into packs, battery management system integration, and end-of-line testing before a pack is released.
Cybernetik builds these stages too, with lines for EV battery pack assembly and for energy storage packs, where testing and classification, AI-driven inspection and MES connectivity carry through to the finished product. The broader view of how a line is planned end to end is in the guide to battery production line design.
About Cybernetik
Cybernetik Technologies is headquartered in Pune, with two design offices, four manufacturing plants and a North American office in Summerville, South Carolina. The company has delivered more than 400 customized robotic automation solutions, and its CleanTech work covers battery pack assembly for EV and energy storage applications along with wind and emission control manufacturing.
Battery lines are engineered for the cells and packs a manufacturer actually makes, and scale from pilot quantities to mass production through modular expansion. Projects are designed, built and tested at the factory before shipping, then installed and commissioned by the same team, with barcode and RFID tracking and MES integration carrying data from the first cell to the finished pack.