Measure internal resistance (requires some equipment to compare between resting voltage and voltage under load) and compare against other batteries of the same make and model and/or against the datasheet (if there was one available).
Measure internal impedance (requires an impedance meter like Vapcell YR1030/1035 or SM8124A) and compare against other batteries of the same make and model.
Charge the battery to a certain value (maybe "storage voltage" around 3.6V - 3.8V would be best?) and observe any sagging in resting voltage over the course of let's say 14 days or 30 days. Cells of good quality should keep their voltage rocksolidly stable. Those with a quickly dropping voltage may have some issues concerning their electrodes inside but I can only guess.
Batteries below a certain resting voltage (IDK, 3.0V or maybe lower than this) should not be charged at all and considered as defective?
I wonder how safe it is to run lithium-ion batteries with a high self-discharge rate. I know that some chemistries have a rather high self-discharge rate but I only saw these in NiCd or NiMH cells before. A lithium-ion battery is a whole different thing, I guess.
BTW, I have (among other batteries) six K64 batteries incoming. They are probably still en route to Europe or being checked by customs (who knows). I will be happy to carry out steps 2 and 3 and report about their status as soon they have arrived.
Oh boy, might have missed this since I've not been keeping track of usage and level. I'll check mine same way, assuming your non-use means you had them sitting loose, not in a flashlight or charger.
I used mine in testing, not sure when, at least couple days ago. They read 3.92V and 4.18V now, and probably not re-charged after use. Recorded the values and time now - will see how they do over the next week on the shelf.
So far after 54 hours, 1 cell no change at 4.18V, the other dropped from 3.92V to 3.71V. Not sure how much usage each got though - wasn't keeping track, but neither got much usage except for high current drain in tests. I'll continue to monitor these 2.
Seems like I may have the same problem maba has above, but for me in just one cell for now.
This is bad news, can't trust these K64's . They disappear from the Ali store, and Dennis doesn't respond here or post what's going on at least.
This is beyond pathetic. I see Dennis has been online several times recently to read and ignore our comments about all the failed cells. So sad that he decided to tuck his tail between his legs and ignore the problem. This has happened at least a few other times with Vapecell, which is why I dont own any of their cells and likely never will.
Don’t forget to file your AliExpress disputes to get your money refunded. If that fails, file a charge-back through your credit card company. Also please leave appropriate negative feedback to warn others. For those who visit similar forums, spread the word so others can avoid this vendor and their disappointing non-existent customer service.
Its alright Dennis… I just did my part on your behalf to allow you to save face and continue hiding your shrunken head in the sand. Maybe you’ll be reincarcerated as a ostrich some day soon, so you can continue doing what comes naturally!
I ordered a few pieces of K64 last April 3. Vapcell/AliExpress gave me a tracking number on April 8. But that tracking number doesn’t give any update at all using multiple tracking sites (17track, postal.ninja, track24, etc. sites) It’s been over 1 month since those K64 have been shipped out, so if they’ll discharge to low voltage, in case I receive the package, then several of them may have self-discharged to low voltages…
Unless you have the ability to test your batteries, I would only buy from a trusted retailer/supplier for now. There’s only 1 US retailer I would buy Vapcells from because they perform their own QC and their QC is at a higher standard than Vapcells. I bought the F14 from them. I don’t have a need for the K64 unless I buy another flashlight and I don’t really want to.
So obviously this sounds like a more extreme case of self discharge but what is an acceptable level of discharge anyways? I suspect re-wrappers don’t promise anything but do OEM’s even publish a spec? You see it in NiMH for instance X% battery life after 6 months in storage. Higher drain batteries tending to have shorter storage life for that chemistry anyways.
Why do people buy re-wrapped cells not knowing what cell is underneath?
The only good 26650 cells i’ve heard of are all based on the PLB55A cells.
I haven’t heard of a cell from PLB greater than 5500mah, and they are like the ONLY manufacturer of 26650s.
There’s no way Vapcell has a “new” cell that gets 6400mah….UNLESS they are “binning” the batteries that test that high, which doesn’t sound like that’s the case.
Also, no response from Vapcell, not a good look for Vapcell….
But hey, they pulled ALL the K64 listings form Aliexpress to prevent people from buying them while they re-evaluate their QC.
Their gold 5300mah G53 26650s I’m pretty sure are based on the PLB55-A, so buy those if you want a pretty looking 26650…
26650s are getting obsolete with very high quality 21700s on the market from Samsung, LG, Sony, Molicel, Panasonic (Tesla), so maybe its time to move on?
. They disappear from the Ali store, and Dennis doesn't respond here or post what's going on at least.