When I said DC internal resistance I mean direct current, not the usually dulled and mostly useless 1KHz AC reading analyzing chargers obtain. Also, the reading at the start of discharge is invalid because the charger measures AC voltage variation injecting AC current into the cell, and I guess it cannot go above maximum cell voltage (and it's there).
To obtain a valid DC internal resistance measurement you need to measure cell voltage variation right at its terminals upon DC current shift out of or into the cell. It can be done with a 4-terminal cell holder, precision power supply or discharge rig, and oscilloscope or precision voltmeter. Without 4-terminal cell holder, the aid of an assistant can help; fellow1 needs to proceed with supply current adjustments while fellow2 needs to hold the multimeter probes at the cell terminals without touching the current leads, and at least one of the two needs to memorize the numbers and do the math.
Diameter is correct as far as I understand. The lenght, however, must be wrong.
So you are thinking some Liitokala blue 5100 are real Liitokala and some might be fake Liitokala 5100? This seems possible.
It is a shame for the company. Their blue and back 26650 were so good. Now we have black 26650 going bad. I don’t think I’ll buy them anymore. The new 5100 seems to have very high internal resistance. Things are not looking good for them.
Only their yellow 21700 4000mah Lishen based cell has a good reputation now.
You can also use your measurement units imho, let people deal with their own issues in this respect if they need to. There are conversion tools everywhere nowadays. I can even convert most of my usual stuff mentally.
Waaay too short for flat top 26650 cells. They usually measure 65mm or a tiiiny bit more. HKJ measured 65 and 65.1mm for the cyan and black cells, respectively. Mangled caliper?
Definitively bad stuff. Open dispute and grab all the evidence you're able comparing them to your blacks discharging in the Zanflare C4. Take good photographs. Fight like the Tsar Bomba.
Buying cells from AliExpress, let me say, is maybe even worse than from eBay. At least in eBay you have PayPal which saves your arse. This is not always the case in AliExpress, and raises cost to some extent. AliExpress is great to buy a nice, good fake. :-)
The Shockli 26650 5500mAh battery from 192led.com are fake, our company never provide any battery to the 192led.com and will not provide them in the future, please be careful of the purchasing.
Please leave message in the forum or email sales@shockli.com for any questions, thanks.
Andrew_Debbie, beware! Since you said “C4” I initially thought you had a Zanflare C4 (which is a lot like the Lii-500), but no! You meant to say “ISDT C4”, which is quite bad. See HKJ's review: Charger ISDT C4 @ lygte-info.dk
Quoting Henrik:
[Quote=HKJ in Charger ISDT C4 review]The charger discharges to 3.1V and it looks like it is adjusting the current trying to keep the voltage at 3.1V.
[/quote]
:facepalm:
[Quote=HKJ in Charger ISDT C4 review]The batteries are charged, discharged and charged again. The charge is not done correctly it is missing the CV part (See below about software update). …
[/quote]
After the update to 1.0.0.11 firmware in the review, with li-ion cell:
[Quote=HKJ in Charger ISDT C4 review]…
A CV voltage has been added to the initial charge in analysis mode and the discharge mode do not slowly reduce current anymore, instead it drops to 0.5A from there sloly reduce current. It looks like the charge failed, there is no CV phase. …
[/quote]
It discharged at 1.5A down to 3.35V, reduced ratio to 0.5A, and finished discharge at 3.05V with a slight tapering…
Without charge top-off tests are invalid unless you start with a properly charged cell (at ≈4.2V resting voltage), and since its discharge behaviour is odd I'd definitively mistrust its figures.