Thanks HKJ. I'm sending you an €4 tip. :-)
That AON7520 MOSFET looks quite powerful. RDS(ON) at VGS 2.5V, ID 20A: typ 2.35mΩ, max 3.1mΩ.
Output regulated MOSFET driver. Combined with a high discharge cell and modding Rsense… 
Cheers ^:)
Got them as expected. 3600mAh is a slight overstatement. 25A is way much overstatement. After doing a discharge on a SKYRC MC3000, I think, it is 99.5% surely a rewrapped NCR18650GA.
Hello!
Received a Samsung INR18650-25R 4-pack from a shady AliExpress seller (217753 store number):
The cells look suspicious. Cell top may be 3x lobe/prong but they do not look exactly like others I've seen in known genuine 25R/30Q cells. They're geometrically a bit different, and seem like dual sheet composed/made. Then the wraps… :facepalm:
I am planning on setting up a way to check out their internal resistance, aided with a precision power supply and a milivolt precision voltmeter. Hope I can render valuable data of it.
Cheers ^:)
Original post date: Mon, 07/16/2018 - 16:55. Edited for a correction.
Petition to HKJ: could you please make a brief test with one of the li-ion cells you're right now testing to make sure the charging dV/I is equivalent to the one exhibitted on discharge? Just to make sure, had a bit of arguing in this respect with Mooch (E-CigaretteForum tester) a few days back.
Cheers ^:)
I’ve tried the charge method of testing Ri and it seemed to be pretty accurate from my small sample size of couple different 18650s compared to actually using an electronic load.
I put up a test script to do it on a SourceMeter where I both charged and discharged with 1A.
Because I use 1A the mV values are the same as mOhm.
I did 11 test each with a charge and a discharge, with 10 seconds between each operation and each operation was 10 seconds long. In the chart I have only included the 8 last tests.
It looks very symmetrical, i.e. charge and discharge resistance is about the same.
Thanks a lot HKJ, result is exactly as I presumed.
I'll briefly test those 25Rs I received. Honestly not yet tested because I've realized a noticeable resting voltage drop a few hours after being settled a little above 3.7V, completely unexpected if you ask me. Thus I'm slowly raising them up to ≈3.8V this time just to check out for elevated self discharge.
AliExpress' cell market, at least with regards to the usual/popular 18650s, is in an alarming state… :facepalm:
:-)
Hi HKJ.,
I am Not sure if this was requested because I have not looked through the entire thread!
How about testing the VTC5D AKA Vapcell IMR 18650 2800mAh 25A?
Thanks 
EDIT: I see it mentioned in post #471 but there did not seem to be a request for it,just showed mooch’s test results.
Here was my capacity test for 2 of them i got from Liionwholesale.
I am looking for never VTC cells, but have not found them yet. I may also test the Vapcell, but it will be called Vapcell.
You can thank Crapcell for buying out the limited production supply of these newer cells and selling them with a different @#$% wrapper at a much higher price. In exchange, the uneducated consumer gets data he/she is probably not up to the task of properly taking advantage of, and the expert gets nothing or even less because nothing beats a datasheet and a genuinely wrapped genuine cell. Did I woke up this morning on my left foot? Probably… 
You can hit the Rude! button now if you wish.
Cheers
You gotta be more rude for that first. 
(By the way, I do not advise that.)
A few weeks earlier I considered to buy a few Samsung 21700-40T, but I cannot justify $20+ for a single cell. Also, I saw Mooch's warning, that he received somewhat poorer performing samples recently from Crapcell (I like this! - also another word came into my mind, but I leave that to the reader's imagination), than they were initially.
Update: It is Fapcell (see? minimal change to reach a goal 
). And yes, Shitecell is also a good name.
Btw, sorry HKJ for jamming the thread, but I could not resist.
Suckcell? 
I'm thinking S***cell.
Aaaw! I believe that's better known as Shitecell among irish and scottish population. :-)
Cheers 
Crapcell? I do not get it. It is a VTC5D RE WRAP. Is it over priced? Yes. Is it a crappy cell? NO.
Let me enlighten you wolfdog1226. Vapcell is doing absolutely no good to us, at least as far as I can see it. There are other cell rewrappers, I know, and despite I do not need them, at least they are trustworthy and reputable (see: EnerCig, KeepPower, …); heck, even their prices are fairer than those of Crapcell…
Has Vapcell abided to an oath which enforces them to use genuine Sony VTC5D cells for the rewrap you mention? No. As far as I understand this, Vapcell cannot be trusted.
I sincerely hope for the big brands to show their awareness with this vaper's fever fashion and they can show better control with where their production goes, even if it is at a higher price. To my eyes there's no better wrap than the original factory wrap; if you can't read/interpret a datasheet and don't like factory wraps and markings, you are clearly unworthy of this stuff. 
Cheers :-)
Ok Sir,your entitled to your opinion. A strong one like mine!! Although I think I may have caused a bit more controversy! 
So what do you think the price[US $] would be if Sony/Murata sold them?
My guess would be $8.50/$9.00,definitely not cheaper than that. My Hometown dealer[Liionwholesale] sells VTC5A for $7.50. Unless their is a sale they won’t be had for less than that[Excluding CHINESE dealers that is].
That still is a lot of money, a lot. I say this because I sometimes assemble/overhaul small battery packs. Just dare to focus on this from this perspective, wolfdog1226, and you'll soon see how cost per unit matters.
I do not think Sony/Murata or any of the big brands is yet interested in consumer retail sales for cells. They aim at the OEM battery pack market, maybe they should also aim at distributors but as far as I can tell they've gone no better than the scare tactics point of view yet there. A potential problem for someone like me is I neither want nor need product price increases in the name of consumer protection. I am not an uneducated complaining consumer, I already know enough to overhaul space constrained laptop battery packs replicating its nickel tabs with copper sheet and soldering them with Bi50Pb32Sn18, for example. For me the rightest price is the lowest one which still ensures me a genuine product. No need to pay for anything else but shipping & handling.