How to track cell lots and grading through pack assembly

Start at the goods inward bench and record the cell supplier, its lot or date code, the cell model and the quantity received. Then photograph the carton label and attach the supplier’s test sheet. Nothing else comes first.

Hold every cell in quarantine until it is graded. An ungraded cell on the shelf must never reach a module build. No grade, no build.

If cells arrive in trays, label each tray and give every graded cell a short code matching its tray position. A printed sign on the quarantine shelf is enough to start, provided the receiving record names who may release cells to grading.

Run each cell through a capacity test on a cycler, measure internal resistance on an AC or DC tester, and record both numbers against the cell code. Rest voltage after storage is a useful third check, because a cell that lost voltage faster than its neighbours is often a poor one.

Set grade bands in advance, such as A, B and reject, and write down who approved them. Keep the bands in one place so two graders cannot apply different rules. Bands change. Date them.

Rejects need a record too. One reason code per reject tray, such as low capacity, high resistance or swollen case, lets you compare supplier lots without reading every grader’s notebook. A bad lot shows quickly.

Cells wired in parallel or in series work best when capacity and resistance sit close together. Build each module from cells of one grade and one lot wherever you can. A mismatched cell drags its neighbours.

Record the matching at the spot welding or bolting station. Scan the module ID first, then each cell as it lands on its nickel strip or busbar position. That gives a list of cell codes by position for that module.

Where rework swaps a cell, record the removed cell, the new one and the reason. Never overwrite the earlier entry.

The module then goes into a pack. The pack serial links down to its modules and each module links down to its cells, and three levels are enough for most builds.

This chain is what a service call needs, since a returned pack with one weak module can be opened and that module’s cell lot looked up in seconds. Three returns sharing a supplier lot make a pattern.

For a recall the chain runs the other way. Start at the lot and list every pack holding even one cell from it, then match those packs to customers.

You do not need everything on day one. Begin with lot code, capacity, resistance and the module scan, and add rework and storage checks later. A paper traveller can carry a pilot batch if every cell code is written legibly and scanned before the module moves on.

Test the chain with a real question by choosing one cell lot and asking which packs contain it. If the answer takes more than a few minutes, find the missing scan and fix that station first.