How to Sort 18650 Lithium-Ion Cells by Capacity?

When it comes to optimizing the performance and longevity of lithium-ion batteries, sorting cells by capacity is a must, especially for 18650 lithium-ion cells used in everything from electric vehicles to portable electronics. Cell sorting plays a big part in improving battery pack performance as well as lifespan. In this article, we will examine the best way to sort 18650 lithium-ion cells by capacity and why cell sorting is required.
Why is the cell sorting in the first place?
Not every lithium-ion battery in all possible chemistries has the same design. In fact, cells have different performances, which can be measured in many different ways (capacity, cycle life, charge/discharge power, etc.). And mainly it is unavoidable that cells do not have precisely the same capacity even if you do everything right.
In case of using unselected cells in series and parallel connections, this later fact leads to some cases where mixing and matching cells can lead to potential damage, especially for Li-ion batteries in a scooter or laptop.
The sorting process
That is why people sort Li-ion cells – basically grouping cells in their family together by capacity. And this involves charging and discharging and putting “identical” cells through its paces, along with meter testing.
Not every company does this, and both cons and pros of making selections (that pertain specifically) to usage comes into play.Categorization
Once each cell has been measured for its capacity, these cell are sorted in ‘categories’. Usually, these categories will be cells with similar voltage and capacity values. The most common capacity values for 18650 cells are 2000mAh, 2500mAh, 3000mAh and 3500mAh. In this way, every battery pack is going to be the same in terms of performance and capacity.
Sorting and Labelling
Once categorize, the cells are then placed in separate bins or trays. This might be done carefully by hand or with a sorting machine. To avoid confusion all cells are marked with a label showing what capacity they are, so the batteries manufacturer and/or technician can find the right cell when assembling the final product.
Testing for Consistency
Following the above steps, it is important to test for consistency. Some cells within the same ‘category’ range may still have slight differences in their performance. A further test is needed to show if the sorted cells are similar or not.
Why Use a Battery Sorting Machine?
A battery sorting machine can go a longway to making the sorting process much more streamlined. These machine will mean that the sorting process is quicker while also helping prevent human error when sorting. Battery sorters like 18650 battery sorting machine and semi-automatic sorting machine are going to save a lot of time and money for the factory going manually.
Key features of a good battery sorting machine
Precision Capacity Testing: Automated capacity testers should be very accurate is sorting; Otherwise it might not valuable to have a sorting machine!
High-Speed: Sorting should also be a quick process, and achieve maximum productivity. That’s simply the point of the whole exercise.
Versatility: It should sort different types of cell (not just for example 18650 but 21700 etc) and also by different parameters too – so sorted by capacity, then Voltage etc.
Quality Control: A good battery sorting machine should pick out cells which are defective, or do not ‘match well’ in a final pack.
Automation of process: A good machine should reduce the need for human help along the way.
Best Practices for Sorting 18650 Cells
Use Testing Equipment that is Accurate: Use a charging system that is highly accurate to avoid missed battery mis-classifications down the line.
Proper Handling of Cells: Your production facility should emphasize good cell handling technique to prevent damage resulting in serious harm later.
Proper Maintenance of Sorting Machines: If using a sorting machine in house then proper calibration of the machine is essential for correct re-test later on.
Be mindful of Temperature in Testing: Lithium-Ion cells care about temperature! When testing ensure cells are at an identical temperature to one another to not impact the result too much.
Conclusion
Sorting of course is vital. Sorting 18650 lithium-ion cells by capacity is a further key step in ensuring performance of a pack made from it. Either help factory dedicate testing, sorting and labelling procedure and machines, or see the sense to not waste your time and end up with a rubbish product yourself.