What are some practical techniques for sorting cells in bulk quickly?

[Redpacket]

You might like to look at some testing flow charts in this thread:

18650 Harvesting Flow Charts

As a community we all have our different ways of processing cells and I wanted to take the opportunity by starting this thread to find some common ground on how we all should harvest cells. This is not meant to be a "be all end all" but more of a guide for new members and maybe some senior...

secondlifestorage.com

Looking for cells to weed out early (before charge/discharge testing) is likely to save a lot of time.
Like Wolf says above, Eg testing for low voltage & poor IR first.

 

[Overmind]

ok, that is so obvious! BUT grabbing a different color all the time would be a pain.. but still a neat idea

Red means 1k, green 500, blue 100. There's no need for higher accuracy than 100 since that's values under are usually tester's tolerances.

 

[jdeadman]

100% Agree Wolf. I have batteries that I have tested good Let sit a Month and are still good. After sitting for 6 months some are showing some self discharge. I realize that is kinda going overboard but all my built packs using the above method are still 97% the same capacity 2 years later. and All in balance. I balance my packs once a year in the summer but they are always monitored

 

[Wolf]

Red means 1k, green 500, blue 100. There's no need for higher accuracy than 100 since that's values under are usually tester's tolerances.

So it would be like a resistor band identifying the cells capacity.
In essence a cell with a 2561 mAh result would look like this?

Wolf

 

[OffGridInTheCity]

100% Agree Wolf. I have batteries that I have tested good Let sit a Month and are still good. After sitting for 6 months some are showing some self discharge. I realize that is kinda going overboard but all my built packs using the above method are still 97% the same capacity 2 years later. and All in balance. I balance my packs once a year in the summer but they are always monitored

>the above method are still 97% the same capacity 2 years later.
@daromer reports X % loss each year from just sitting around. I'm curious - do you store them at 3.6/3.7v? What's your experience with regard to capacity loss from sitting?

 

[daromer]

Papers state around 3-10% loss per year in total capacity just sitting. Note that it depends on cell type.
I have 6 years new-old stock cells. They had Lost around 5-8% in total over this time. Bur they were Stored basically empty and had a max shelf life of 3 year from that manufacturer.

So it all depends.

I dont think its an issue leaving Them for some time but based on papers they loose alot more when fully charged in terms of life compared to 4.0 or even 3.6 or below. That is a fact. The amount varies

 

[jdeadman]

the Capacity tests are my active packs capacity. For these packs in service they are held to 4.05V to 3.6V per cell but for the most part their cycle depth is really shallow.

The cells tested were sitting for 6 months held a set voltage of 3.8V set by a digital voltage PS that I have connected to a large parallel cell holders to make sure the cells don't sag or recover to a different voltage. once stable they get shevled My voltage drop limits are within the 5-8% capacity

 

[Overmind]

@Wolf yes, but the dots I put on the bottom and are very small.
Example (pic is from the net). Dots can be distributed not to look ugly also.

 

[anton_voltx]

Everyone else gave good advice and decent procedures. If you plan on processing 3k cells often, there are also automated machines for cell sorting by voltage/capacity that we use.

 

[OffGridInTheCity]

Everyone else gave good advice and decent procedures. If you plan on processing 3k cells often, there are also automated machines for cell sorting by voltage/capacity that we use.

I just finished processing 2500 cells over the last 7 months - so this sounds fantastic. What is the machine / how does it work? Does it do a charge/discharge test or read lables to get capacity? Does it report IR? How much?

 

[anton_voltx]

I just finished processing 2500 cells over the last 7 months - so this sounds fantastic. What is the machine / how does it work? Does it do a charge/discharge test or read lables to get capacity? Does it report IR? How much?

For speed it's usually sorted by voltage/resistance. For example we have used a machine similar to this:

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But there are more mechanical / simpler solutions that I think can get closer to $2000. So I'm not sure 2500 cell in 7 month justifies industrial equipment but I suppose it depends how much you value your time

For capacity testing we use big racks that will measure the cells while they charge/discharge. You can get these anywhere from small 16 channel to big 256+ channel cabinets. There is no automatic sorting though, just run-of-the-mill capacity testing (but that makes sense when you consider the time needed for capacity tests and how small a proportion the actual sorting process is comparatively).