Do any sellers actually test the Li-Ion cells they sell ?

[march.brown]

Some sellers/retailers of Li-Ion cells have a better reputation than certain other well-known Far Eastern retailers.

Do these sellers of "better quality" cells actually test the cells that they sell to us ? ... Do they test a sample of each batch of cells that they import ? ... If so is it one in every batch or a random selection of perhaps one in every hundred or so ? ... Are they tested for capacity plus the safe operation of the protection circuit (if fitted) ?

Do these reliable sellers accept the word of their suppliers that the cells are top quality ? ... Do the original manufacturers test every cell so as to grade them by capacity etc before passing them on to the distributers/wholesalers ?

It would be nice to know the actual supply chain sequence and at which point the testing occurs ... When these cells are fitted with the protection circuits , are all the protection circuits tested prior to installation ? ... Are they all tested in any way before we receive them ?

Is it still a matter of luck , even with the more reliable sellers ? ... As a user of 18650 cells , I think it would be useful to know if any of our cells are tested in any way before they reach us.

It would seem that the 18650s are made specifically for power packs used in laptops and cordless tools with none made specifically for torches ... So it looks as though the cells that we buy are either surplus to requirement of power pack builders (for some reason) or they are rejects.
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[Meterman]

I remember the cost of an IC (don't remember the type) - about 30 years ago - in untested version was less than 1.00DM. The version tested to NASA specification including burn in was about 600DM.

I'm afraid the cheap cells we get are not more than counted, if not only weighed.

Wulf

 

[45/70]

Hi march.

I doubt many sellers test every cell, some may, I really don't know.

As far as the variation in quality of the cells we get, I think it has a lot to do with how close the seller is to the source they obtain cells from. Those that have a close relationship, likely have a choice to obtain better quality cells. These cells will no doubt carry a premium which will be reflected in the final price we pay, and those that aren't the best will end up selling for less.

I think the general rule of "you get what you pay for" applies to Li-Ion cells, just like anything else. This has been my experience anyway in the 5 or so years I've been buying Li-Ion cells. While not directly proportional to cost, the $4 18650 never seems to perform as well as the $10 18650. This may not be so noticeable when new, sometimes it is, but as the cells age, it becomes more evident.

One likely reason for this, is some cells may be of a more recent manufacture than others. Again, these will very likely cost the dealer more and be reflected in the final price.

Dave

 

[jasonck08]

It's definitely not possible to test every single cell for capacity, as a charge, discharge and recharge process could easily take 4-5 hours per cell.

I'm sure most IC companies have some sort of QC where they test every IC for basic functionality before sending it out for installation on a battery.

Most cells from reliable manufacturers are all sent out at the same voltage (~40-50%). If your sorting through several hundred cells and measuring the voltage and almost all the cells measure 3.75v and you find a couple that are in the low 3v range, then it would be a safe assumption that something is wrong with the lower voltage cells. In that case I would test the cell prior to shipping it to make sure its up to spec.

As far as quality goes, there are several big players out there. There are about 6 or so well respected Chinese Li-on battery companies, some of which manufacturer for big companies like Apple. And then there are the well known Japanese and Korean companies like Sony, Panasonic, Sanyo, LG, Samsung etc. All of these companies have very good quality control, and dud cells are rare, because they are all made to such strict specifications.

 

[march.brown]

It's definitely not possible to test every single cell for capacity, as a charge, discharge and recharge process could easily take 4-5 hours per cell.

I'm sure most IC companies have some sort of QC where they test every IC for basic functionality before sending it out for installation on a battery.

Most cells from reliable manufacturers are all sent out at the same voltage (~40-50%). If your sorting through several hundred cells and measuring the voltage and almost all the cells measure 3.75v and you find a couple that are in the low 3v range, then it would be a safe assumption that something is wrong with the lower voltage cells. In that case I would test the cell prior to shipping it to make sure its up to spec.

As far as quality goes, there are several big players out there. There are about 6 or so well respected Chinese Li-on battery companies, some of which manufacturer for big companies like Apple. And then there are the well known Japanese and Korean companies like Sony, Panasonic, Sanyo, LG, Samsung etc. All of these companies have very good quality control, and dud cells are rare, because they are all made to such strict specifications.

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If I buy non-protected cells , is there any way that I can tell who originally made the cell ? ... Is there any makers stamp or mark to be seen ? ... Are there any marks under the plastic sheath for example ?

I assume that other than the "big six" manufacturers there are other lesser manufacturers with poorer quality control ... Just wondering if there was a means of finding out where the cells originated.
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[jasonck08]

.
If I buy non-protected cells , is there any way that I can tell who originally made the cell ? ... Is there any makers stamp or mark to be seen ? ... Are there any marks under the plastic sheath for example ?

I assume that other than the "big six" manufacturers there are other lesser manufacturers with poorer quality control ... Just wondering if there was a means of finding out where the cells originated.
.

It can be difficult to tell a lot of times. The top Japanese and Korean cells are easier to identify because they are used so widely in laptop packs. You can slit open the plastic sleeve and sometimes see markings on the cell that will give you some clues. Some manufacturers don't mark the bare metal, and only mark the plastic sleeve. So if that was replaced by a 3rd party and rebranded under another name, it would be hard to tell.

Sometimes you can take the measurements of the cell by using a micrometer as well as the top positive connection end to compare it with other cells from known manufacturers. The design of the + connection varies from manufacturer to manufacturer.

Another way to tell is to get a selection of cells from known manufacturers and then do discharge tests at a specified current using something like the CBA analyzer. Then you compare the curve with cells from "unknown" manufacturers. This has helped me identify a cell before, because the discharge curve matched another cell form a known manufacturer exactly. And the measurements of the cell also matched, it was simply rebranded by another company.

 

[VidPro]

You can find sellers that will do some testing of the cells.
even DX and KAI have shown their testing of cells every once in a while.

candlepower markeplace sellers will often show thier own testing results on lights, drivers, and batteries they are going to sell to us.
because they know that information is usefull, and of interest.

when you see "notes added" that did not come from manufactures , like "tested to", "has minimum capacity of" , "tests higher" , Thier Own graph item, that is different than the spec sheet.
many of the dealers i have been to , you can see a array of testing equiptment, they are either applying, or just using to keep thier stock alive.

"pack makers" the high end people who will make/remake a battery pack for you, can be some pickey people. they SAY (at least) that they test every cell item they put in your pack, because they want the pack to be initially balanced. When i make/remake my packs, testing every cell for "close enough" is very time consuming, and slows the whole process down.
Like Jason said, if one is suspicious looking from the others, then you gotta wonder about it. could mean nothing, or could be the one you dont want to use, but it stands out, and now i for SURE have to test

 

[liveforphysics]

Some do. It takes roughly 2minutes of labor time, and 2hrs of machine time per cell. On large packs, or packs for critical applications, it's too expensive not to check every cell that goes in a pack.

For cells not going into packs, I think most folks would rather have dirt cheap cells, and get a bad one once in a while than pay for cycled and/or capacity binned cells.