How to Sort Prismatic Cells by Voltage and IR?

Introduction
Prismatic cells are most used on the EV, ESS and power stuff. They are rectangular thus you can pack them pretty good in a battery pack. Amongst other stuff necessary for that pack management is to sort them per their voltage and IR, so they operate optimally and also is extending the actual lifespan of the whole pack, since you are not risking overcharging and over discharging.
In this article we will take a deep dive into the why and how of performing that activity.
Why is This Important?
Voltage: Sorting in theory can make sure that all cells are at the same voltage level. If cells of different voltages are mated together, the weakest of the party will (may) drain quicker, causing their actual battery life shortening. The voltage consistency allows each to be charge/discharge at the same rate, thus effecting the pack perform better.
IR measurement: If much bigger values of IR are measured cell may be rejected. Since IR is a measure of performance this may help to weed out cell that would consume (take/loose) a more important part of available energy going fro a charge or discharge and excessive heat being generated.
Battery Management System (BMS) Optimization: Sorting prismatic cells by voltage and IR helps the BMS to effectively monitor and manage the cells, ensuring that the battery pack is operating efficiently and reducing the risk of imbalancing them there, and consequential charging/discharging issues. These issues can lead to battery degradation, capacity loss, and possibly battery failure.How cells are sorted
First obtain a prismatic cell sorting machine; they are capable of both measuring the voltage/IR & sorting the cells as required. Some machines are semi-automatic, others fully (& thus faster) automated. To sort cells you first have to measure each cells internal resistance [IR]. Many clearing machines have an IR tester built in for this task—you must check the IR of each cell prior to sorting; some machines are a desk silhouette, or bench designated specific to prismatic cells with integrated conveyors. Now, on to the measuring & ranking, how is this achieved?Most clearing machines now come with a voltage tester that quickly checks the voltage of each cell. Cells that are roughly in the same performance capability can be grouped together, whilst those acceptable only if voltage that is too high or too low should be rejected.
3. Measure the Internal Resistance
Next you’ll also want to measure the Internal resistance of each cell. As internal resistance is a good measure of how efficient (and hence how good) a cells actually is, it’s very important to measure this. An IR tester is built into the sorting machine that you simply place each cell within and a small current is drawn from it, allowing it to measure the drop, and from this work out the resistance.Cells with a high IR should then, ideally, be placed to one side of those with a lower IR (ideally, the prismatic cells with a high enough IR should be binning for replacement, or sent for testing to see if there is a defect somewhere)
4. Sort Cells By Voltage And IR
With those two, the cells can be sorted into separate categories. Usually, cells will be sorted into groups based on (but not limited to): Voltage Range (eg. 3.6v, 3.7v, etc.) IR Range (could simply be low, medium, high)
Cells with a similar level of voltage and IR should kivu;ngroup together. That will help maintain the efficiency of the battery pack—and means all the cells work well together, in the system.
5. Store the Sorted Cells
Now that you’ve sorted them, also take proper care in storing these cells. The bins or trays with the prismatic should, not just be marked, but placed a part from those not marked. It should be kept in an empty unit next to the trifling bag or receiving tray, or wherever, you know best fit at storing cells, to get at them should you want to assemble them in a battery pack.
Key Considerations for the Sorted Cells?
Just be conscious of:
Accuracy of Measurements: The tests of course should be accurate, so you should use high quality testers along with quality equipment as well.
Auto-Sorting Machines: Manual sorting is an option, but usually the machines can take care of this more efficiently—and quickly too.
Environmental Influences: Issue of paper is raised (or more so eluded to for jokes), and should think of temperature, humidity, and actual handling itself. Poor handling could destroy your cells, excessive heat could mean failed cells—so the more a classified machine and a tech machine, the better.