Influence of DOD and temperature on the internal resistance

[bellfador]

[/quote

DCIR = (U2-U1) / (I1-12)

Maybe now is easy to understand.

 

[okashira]

Can you test all three of your graphene cells to look at the consistency?

 

[bellfador]

I will try to do that soon.

 

[bellfador]

Another 2 cell from LiPo Graphene 1.5Ah 65C pack is added.

After 2 cycles with +1A / -1A and 3 cycles with +2.3A / -4A:

Cell2: 1487 mAh from SkyRC B6 @1A;
1453 mAh from the battery tester 0.9A / 8A;

Cell3: 1490 mAh from SkyRC B6 @1A;
1465 mAh from the battery tester 0.9A / 8A;

 

[Matador]

Awesome post ! That's some serious data right here

 

[Matador]

It would be amazing if Justin from eBikes.ca could make a "Lithium Cell Simulator" just like they did with the "Motor simulator".

For each brand we could have :
DCIR and ACIR versus temp and versus state of charge
discharge curves of volts vs mAh for different amp loads
Number of cycles of different brand at their rated max discharge rate or lower rates.
etc...

That would help choosing. I'm looking to buy 18650 in the future. I'd like them to live the longest possible life. I'd be a 14S13P pack with high-amperage wiring (copper) to each cells whith parallel connection for every cells.
I have a 30 amp BBSHD.
But I'd like to know what's the best 30A/cell 18650 out there. Some cell truely able to handle thoses 30A per cell continuous load without heating and loosing capacity. Having the lowest possible DCIR... Still in the 30A/cell-realm, there's probably one that of cell that has the best value, the best usefull life and still a reasonable mAh rating (range).

Samsung :
- Samsung INR18650-25R 20A 2500 mAh [LiNiMnCoO2] (datasheet : http://www.bto.pl/pdf/06248/INR18650-25R.pdf ; https://www.powerstream.com/p/INR18650-25R-datasheet.pdf )
- Samsung INR18650-30Q 15A 3000 mAh [LiNiMnCoO2] (datasheet : https://www.kupifonar.kz/upload/itemimg/samsung/18650-30q/samsung-30q-specification.pdf ; https://eu.nkon.nl/sk/k/30q.pdf)

LG :
- LG ICR18650-HE2 20A 2500 mAh [LiCoO2] (datasheet : https://www.powerstream.com/p/LG-ICR18650HE2-REV0.pdf)
- HE4 20 amp (found no legit datasheet/specsheet)
- LG INR18650-HG2 20A 3000 mAh [LiNiMnCoO2] (datasheet : https://www.nkon.nl/sk/k/hg2.pdf ; https://vk.com/doc81686429_437468687?hash=caf8d9f583d5b15fbd&dl=7592133a57a67a7f2a)
- LG ICR18650-HD2 25A 2000 mAh [LiCoO2] (datasheet : http://www.houseofbatteries.com/documents/5216-BatteryLines/LGLithiumIon18650HD2Rechargeable.pdf ; http://www.keeppower.com.cn/products_detail.php?id=492)
- HB6 30 amp (found no legit datasheet/specsheet)

Sony :
- Sony US18650-VTC3 30A 1600 mAh [LMn2O4] (datasheet : https://www.imrbatteries.com/content/sony_us18650vtc3.pdf)
- Sony US18650-VTC4 30A 2100 mAh [LiNiMnCoO2] (datasheet : https://www.powerstream.com/p/us18650vtc5-vtc5.pdf ; https://www.powerstream.com/p/us18650vtc4.pdf)
- Sony US18650-VTC5 20A 2600 mAh [LiNiMnCoO2] (datasheet : https://www.lemona.lt/LIUSE/TI/En/Pdf/18650-2600-SONY.pdf)

Sanyo :
- Sanyo UR18650-NSX 20A 2500 mAh [LiMn2O4] (datasheet : https://cdn.shopify.com/s/files/1/0674/3651/files/sanyo_ur18650nsx_spec_sheet.pdf?2358184305725242569) ; (testing : https://www.e-cigarette-forum.com/forum/threads/sanyo-ur18650nsx-20a-2500mah-18650-bench-test-results-a-great-22a-battery-about-equal-to-the-25r5.734699/ they seem to got hot at 20A!)

Panasonic :
- Panasonic NCR18650PF 10A 2700 mAh [LiNiCoAlO2] (datasheet : http://www.rc-electronic.com/downloads/pdf/infos/datasheet_LiIo_Panasonic.pdf ; https://eu.nkon.nl/rechargeable/18650-size/panasonic-ncr18650pf-3-7v-2900mah.html)
- Panasonic NCR18650GA 10A 3300 mAh [LiNiCoAlO2] (datasheet : https://www.nkon.nl/sk/k/ncr18650ga.pdf)

I'm starting to become hesitant.... LiFePO4 and LiNiMnO2 seems like the best allound choices : http://batteryuniversity.com/learn/article/types_of_lithium_ion

 

[Punx0r]

If you have a 13P pack and a 30A BBSHD, why would you be looking for cells capable of a 30A continuous discharge? You actual discharge is going to be less than a tenth of that...

 

[Matador]

If you have a 13P pack and a 30A BBSHD, why would you be looking for cells capable of a 30A continuous discharge? You actual discharge is going to be less than a tenth of that...

Yes, but I was thinking that cells seeing a very small load relative to what they would be capable of delivering would increase their life lenght significantly even if I push 30 amps on my controller all the time. In all honesty, 30 amp cells might be really overkill, but I'm looking for a sweet spot between Life (nb of cycles), Power (Max Amps), Range (mAh). Also, I might overclock my 30 amps controller to 45 or even 60 amps in the future with a mod discribed on one of the ES thread (adding a shunt, changing mofsets). See, with 13P, range is not so much an issue anymore. I'd rather have longer cell life... So cells seeing 0.08C, 0.12C or even 0.16C should preserve them... At these C rates, they would basically see NO temperature rise. I also think that specs on 18650 are often a bit inflated. I doubt 10A rated cell will live very long if always pushed to 10A rates. I want headroom, lot's of headroom.

If done experiment with a shitty 14S9P battery pack made of selected 18650 form laptop batteries rated 5.2amps at 2C... Well sure they were old, but I've selected the one with more than 80% of rated capacity, DCIR less than 150 mOhm and no voltage drift more than 0.2 volts in 6 months.... Still after 200 km, my battery deteriorated much (on average, I lost 15% capacity... but might have something to do with the high resistance springs I use in my solderless build).
I know laptop cell are shit, but a get a feeling headroom is a good thing.

 

[Hillhater]

Sorry to revive an old post, but i was just refering back for info and noticed on the VTC5 test something odd..
A) you seem to have increased the charge voltage to 4.2v from the 4.1 for the previous cells ?
B) that cell also seems to last nearly twice as long (7000s) as any of the previous tests ?
Did you change the test protocal/ timings somehow ?....longer time between discharge pulses maybe ?
......but that would influence the temperature build up ?

VTC5A is added.
2460 mAh from SkyRC B6 @1A;
2400 mAh from the battery tester 0.9A / 8A;

;

Weight: 47.34 g

 

[Hillhater]

?.......
But I'd like to know what's the best 30A/cell 18650 out there. Some cell truely able to handle thoses 30A per cell continuous load without heating and loosing capacity. Having the lowest possible DCIR... Still in the 30A/cell-realm, there's probably one that of cell that has the best value, the best usefull life and still a reasonable mAh rating (range).......
n

No such cell exists to suit all your expectations......
...but probably the closest is the A123 M1 which has the life and powerability, but sacrifices capacity.....and cost.!

 

[Matador]

No such cell exists to suit all your expectations......
...but probably the closest is the A123 M1 which has the life and powerability, but sacrifices capacity.....and cost.!

Do you think that the life is worth the extra cost ?

 

[bellfador]

Sorry to revive an old post, but i was just refering back for info and noticed on the VTC5 test something odd..
A) you seem to have increased the charge voltage to 4.2v from the 4.1 for the previous cells ?
B) that cell also seems to last nearly twice as long (7000s) as any of the previous tests ?
Did you change the test protocal/ timings somehow ?....longer time between discharge pulses maybe ?
......but that would influence the temperature build up ?

VTC5A is added.
2460 mAh from SkyRC B6 @1A;
2400 mAh from the battery tester 0.9A / 8A;

;

Weight: 47.34 g

This are different tests. First is test for internal resistance ( around 7000s), second is pulse mode tests (around 4000s).