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[bibo164]

Hello,

I have a source for BRAND NEW LG INR21700 M50T Cells. They are factory new and have never been used.

I am using them myself and would like to understand if you are also interesten in them? For that please write me a pm or comment how many cells you would order and where you live. From this I can figure out how much demand there is and how I could best sell them to you. Please only write me if you seriously consider buying them.
I live in central Germany and would ship to the EU for now. The price may vary depending on interest/quantity.

The cells are immediately available to me, so once there is enough interest I could start shipping.
These are NOT 18650 Cells, they are slightly bigger 21mm x 700mm!

LG INR21700-M50T 5000mAH / 7,5 A continuous / 15 A peak
3,99€/cell + shipping
>100 cells 3,89€/cell + shipping



Max. cont. charge current:
0 ~ 25°C 0.3C (1,455mAh)
25 ~ 45°C 0.7C (3,395mAh)

Max. cont. discharge current:
-20 ~ 10°C 0.5C (2,425mAh)
10 ~ 25°C 3.0C (14,550mAh)
25 ~ 55°C 1.5C (7,275mAh)

 

[john61ct]

What assurance that they are genuine?

Have you run your own cap tests?

 

[bibo164]

I will do proper capacity tests over the weekend and share the results.

There is in fact no guarantee that they are genuine but all the infos I have add up.

I can send send you a couple of cells at a discount for testing and confirming their quality. Please let me know if you are interested.

 

[Merlin]

but....beside no heatshrinks and me wondering why they circle around when they are "genuine"...this is the NKON price from a well known international seller company with tax and invoice.

....i mean. you are selling ....private.

if you have a source of 20700 sanyos.....well...than iam in

 

[bibo164]

You are right, so I adjusted the offer with prices for the expected quantities and made a special offer for anyone who wants to check out those cells and give some feedback. Cap tests will follow over the weekend.

 

[Merlin]

capacity test is nice but what counts is internal resistance. thats the only thing that says something about in relation to capacity.

you can squeeze out maybe 5Ah out of it using just 0.5a current.
but if you have "grade C" cells and discharge them with 7.5A continue they may have only 4Ah.

 

[bibo164]

Hello,

so here some more infos on the cells:


The cells were supposed to end up in these 13S1P packs for a german OEM. Because for whatever reason this project was scrapped so they had to get rid of the already manufactured packs and the rest of the cells. Unfortunately the fully equipped packs were discharged to 0V so they can only be scrapped.
I took one pack apart and equipped it with new cells but the BMS does not come on. If someone thinks he can reverse engineer this BMS please contact me.


so I did several Tests with the cells:
1. Internal resistance test: I never measured any value above 60mOhms
[youtube]Gjfki-W6uVU[/youtube]

2. 5-7A Discharge (maxed out my charger) Result: 4790mAh
[youtube]onBMhaVWftA[/youtube]

3. I configured a 13s1p pack and discharged it through an inverter with 7.5A to 3.35V per cell (inverter cut-off) - Result: 2.52Ah
[youtube]R2BnkjFNHuY[/youtube]

 

[john61ct]

The problem is, very difficult to get a "standard" consistent measure of ESIR, without tightly specifying a dozen different conditions.

A pure cap test is always done at super low current rates, 0.01C would be the highest if trying to confirm against the nameplate rating.

This is no verification of "A" vs "B" production runs, that really depends on the reputation of the supply chain.

But assuming they are not counterfeit, at least verifies they are new or at least in good shape, not worn second-hand.

If you start testing for high C-rates without too much voltage drop or heat build-up

that is no longer a cap test, more like the "real C" tests we see members perform to rate brand quality, like ESIR requiring lots of variables to be spec'd and held constant and beyond what most sellers would allow before purchase.

capacity test is nice but what counts is internal resistance.

 

[lesta]

Pm sent

 

[Cheburator]

Cells received, thank you!
I have tested 3 cells to check the consistency of parameters.
Each cell weights 68.6g, are at 3.58V and my YR1035 shows internal resistance of 22 mOhms. Cells come completely naked without any signs of use. I have added top insulation sticker and shrink wrap for extra safety.

Capacity test at 1A showed about 5Ah.

https://i.postimg.cc/L68h52YL/P2080274.jpg
https://i.postimg.cc/50J2VVWH/P2100276.jpg

Capacity test at 7.5A showed about 4.8Ah.

[youtube]www.youtube.com/watch?v=u4zRYvkYTz0[/youtube]
[youtube]https://youtu.be/pXVEqKn1t80[/youtube]
[youtube]https://youtu.be/LZYLJYLt0n8[/youtube]

After all tests internal resistance have not changed.
So I can say that these cells are genuine and new, all parameters correspond to datasheet.

 

[john61ct]

Very nice results!

Fact that capacity drops so little going from 0.2C to 1.5C a great sign.

What was your LVC on those tests?

USD $270 per kWh

OP please quote for 50 units, with shipping to NYC, slow is fine but tracked of course

 

[Cheburator]

What was your LVC on those tests?

I discharged to 2.5V as I tried to follow the datasheet instructions as good as I can.

 

[john61ct]

Yep that is right for benchmarking, but not something to do routinely

The vendor test for nameplate rating was likely half an amp or even the 20-hour rate

 

[serginho007]

Anybody knows how fast we can charge these 21700 cells? Let say standard Chinese 18650 (13S 15A), they recommend to charge with 2amp, I've got 14s 34a and charging them with current 4-5 amps.

So what would recommend for these 21700?

 

[john61ct]

If you want good cycle lifespan, 0.4 to 0.5C rate.

Going higher, longevity hit is reduced by ensuring the cell is at warm to hot temperatures first.

Obviously if the other care parameters are "abusive" (not conducive to good lifespan) like high **discharge** rates, or high average DoD%

then this one factor's impact won't be so influential.

If you really want fast charging and don't care about cell lifespan, just trying to prevent fires,

then maybe 2-3C will be OK, but best to measure temperature rise and stop / slow things down before getting to 110°F

 

[serginho007]

If you want good cycle lifespan, 0.4 to 0.5C rate.

Going higher, longevity hit is reduced by ensuring the cell is at warm to hot temperatures first.

Obviously if the other care parameters are "abusive" (not conducive to good lifespan) like high **discharge** rates, or high average DoD%

then this one factor's impact won't be so influential.

If you really want fast charging and don't care about cell lifespan, just trying to prevent fires,

then maybe 2-3C will be OK, but best to measure temperature rise and stop / slow things down before getting to 110°F

Thank you john61ct

Good lifespan is what I'm looking for!

I believe rate 0.4 would be only suitable for any 21700 or maybe for 18650 as well?

As I just looked to data sheet, Samsung INR18650-35E can be charged 0.5C, so based on that my 52v 34A pack I can charge easily with 15A charger with no effect to lifespan, correct?

 

[john61ct]

Yes.

These mumbers are consistent for all "li-ion" chemistries in the 3.6 - 3.7V range, physical size makes no difference

But be aware there are no "bright lines" black and white

Everything affects longevity in a grey-scale curve

So everything is a judgment call.

0.1C is gentler than 0.4C, and 0.5C is only a little more stressful.

Good rule of thumb is keep any heat rise **internally generated** from chemical activity to very low, ideally undetectable.

But pre-heating **from outside** when ambients are cold

reduces harm from high C-rates.

 

[serginho007]

Yes, thanks again. Very clear explanation. Helps a lot...