Samsung's new 21700-30T Tested by Dampfakkus

[Jason McNeil]

Has anyone seen these new pups from Samsung? Capacity is 3.5Ah for a larger cell (47% increase in volume than the 18650) so nothing impressive there, but what's damned remarkable is the Internal Resistance spec, just 10mΩ. This is astonishingly low; by comparison, some of the best 18650s in this class, like the Samsung 30Q & the LG HG2 are about 20mΩ. 

The guys tested 35A (that's 130W sustained output from one tiny little cell!!!) discharge and temperature was just 75°C. Probably still not up to @EUC Extreme's extreme requirements yet, especially for the fast-charging, but it's interesting to see that this larger cell delivers higher performance characteristics.  

EDIT: there's a guy from Denmark on the http://budgetlightforum.com forum who also maintains a performance database of cells. His conclusion was "This battery is a very good battery and the best high current cell I have tested to date."

http://budgetlightforum.com/node/53534

[EUC Extreme]

I have not seen such a thing. It would be nice to test.
Where to get them?

[Carlos E Rodriguez]

it looks like the 21700 is the Elon Musk Tesla proprietary battery. It bigger and better.

[esaj]

36 minutes ago, Carlos E Rodriguez said:

it looks like the 21700 is the Elon Musk Tesla proprietary battery. It bigger and better.

The way I've understood it, the 21700-form factor is not proprietary, just that Tesla is developing their own proprietary cell that uses that form factor. Other manufacturers have been doing those too, they're just not used in Teslas.

Bigger, yes, but better? I guess it depends how you measure, it's larger, so you can store more energy in single 21700 than in single 18650. But it will be heavier and take more space, I don't know if they've managed to make the energy density any better, but in this specific case (Samsung INR21700 30T  http://www.dampfakkus.de/akkutest.php?id=673), they've managed to get the internal resistance to a very low value. There are also even larger sizes of 26500 and 26650, some of those are claimed to be able to go up to 50A continuous current (3.7V * 50A = 185W), don't know if it's true (on a quick glance, the lowest internal resistance I found on 26650's was 19 milliohm).

 

 

[US69]

17 minutes ago, esaj said:

larger sizes of 26500 and 26650, some of those are claimed to be able to go up to 50A continuous current (3.7V * 50A = 185W), don't know if it's true (on a quick glance, the lowest intern

From vaping i can tell you that these 26' cells are not as good as the numbers stated! The 50amps are , when at all,short peak!

Even for a 10-20Amp  continuous are needed, 18650 are the better choice.

when very high amps are needed the VTC5/6 from Sony are the way to go.

[Jason McNeil]

@KingSong69 will you be vaping with the 30Ts? There's already talk over on the vaping forums about dustING off the lathes to fit these cells. 

[US69]

13 minutes ago, Jason McNeil said:

@KingSong69 will you be vaping with the 30Ts? There's already talk over on the vaping forums about dusty off the lathes to fit these cells. 

Private "mod" makes perhaps will jump on this train. But At all the "cloud chasers" and ultra "sub-ohmers" are not the majority of vapers. but these geeks will try this cell, for sure :-)

For the chinese produced mass market batterie mods, which dont need more than 10 Amps or even lower, i can not see why to produce complete new batterie sled/mods when you can get 30Amp with a vtc6 by just 400-500mah less.

Most vapers (vaping under one ohm) using the lg hg2.....continous 20Amps...and not so crazy expensive as the Vtc series.

I am old school using the Samsung 25R :-) And just change the batterie a bit more often....

[thefork]

1 hour ago, esaj said:

I don't know if they've managed to make the energy density any better

In this case, no. Doing some math, the 18650 has a volume of 16540.5 mm3 (cubic millimeters), whereas the 21700 has a volume of 24245.2 mm3. That's an increase in volume of almost 47 percent.

[MetricUSA]

Tesla is partnering with Panisonic which has 20700 cells and looks like Tesla added additional safety circuitry to the top if you look at other 21700 battery pics...

[Jason McNeil]

Official datasheet is out for the NCR20700A cell & the longevity data isn't great at all.

There's a 33% linear degradation rate from 0-300 cycles. I find it anomalous that the 10A & 20A discharges have exactly the same curve, while the 30A discharge has a bigger gap (as you would expect). If used for EVs, there's going to be a pretty substantial capacity penalty over time.

https://akkuplus.de/mediafiles/Datenblatt/Panasonic/Panasonic_NCR20700A.pdf

[esaj]

1 hour ago, Jason McNeil said:

Official datasheet is out for the NCR20700A cell & the longevity data isn't great at all.

There's a 33% linear degradation rate from 0-300 cycles. I find it anomalous that the 10A & 20A discharges have exactly the same curve, while the 30A discharge has a bigger gap (as you would expect). If used for EVs, there's going to be a pretty substantial capacity penalty over time.

https://akkuplus.de/mediafiles/Datenblatt/Panasonic/Panasonic_NCR20700A.pdf

Things that probably affect the poor cycle count are that they've used high charging current (6A, almost 2C for 3200mAh cells), pretty much the maximum possible 4.2V -> 2.5V cycles, and discharged with continuous high currents (10-30A). Still, it's not exactly stellar when it comes to the cycle lifetime    Of course in real use, you don't use that high currents all the time, and the wheels usually force you stop around 3.0V / cell?

Compare that to what Battery University says about the usual cycle lifes for the lithium-batteries (  http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries  ), although they seem to define 100% depth of discharge as 4.2 -> 3.0V :

Figure 1 illustrates the capacity drop of 11 Li-polymer batteries that have been cycled at a Cadex laboratory. The 1,500mAh pouch cells for mobile phones were first charged at a current of 1,500mA (1C) to 4.20V/cell and then allowed to saturate to 0.05C (75mA) as part of the full charge saturation. The batteries were then discharged at 1,500mA to 3.0V/cell, and the cycle was repeated. The expected capacity loss of Li-ion batteries was uniform over the delivered 250 cycles and the batteries performed as expected.
 

Figure 1: Capacity drop as part of cycling. Eleven new Li-ion were tested on a Cadex C7400 battery analyzer. All packs started at a capacity of 88–94% and decreased to 73–84% after 250 full discharge cycles. The 1500mAh pouch packs are used in mobile phones. Courtesy of Cadex

Depth of discharge	Discharge cycles (NMC / LiPO4)	Table 2: Cycle life as a function of depth of discharge. A partial discharge reduces stress and prolongs battery life, so does a partial charge. Elevated temperature and high currents also affect cycle life. Note: 100% DoD is a full cycle; 10% is very brief. Cycling in mid-state-of-charge would have best longevity.
100% DoD	~300 / 600
80% DoD	~400 / 900
60% DoD	~600 / 1,500
40% DoD	~1,500 / 3,000
20% DoD	~1,500 / 9,000
10% DoD	~10,000 / 15,000

 

 

Charge level (V/cell)	Discharge cycles	Available stored energy	Table 4: Discharge cycles and capacity as a function of charge voltage limit. Every 0.10V drop below 4.20V/cell doubles the cycle but holds less capacity. Raising the voltage above 4.20V/cell would shorten the life. Guideline: Every 70mV drop in charge voltage lowers the usable capacity by about 10%. Note: Partial charging negates the benefit of Li-ion in terms of high specific energy.
[4.30]	[150–250]	[110–115%]
4.25	200–350	105–110%
4.20	300–500	100%
4.15	400–700	90–95%
4.10	600–1,000	85–90%
4.05	850–1,500	80–85%
4.00	1,200–2,000	70–75%
3.90	2,400–4,000	60–65%
3.80	See note	35–40%
3.70	See note	30% and less

 

[Jason McNeil]

28 minutes ago, esaj said:

Things that probably affect the poor cycle count are that they've used high charging current (6A, almost 2C for 3200mAh cells

Good spot, that would make sense! I wonder what compelled Panasonic to run such an unfavourable test?!  Was it a joke of some bored Panasonic Engineer "Let's put these cells under conditions which will kill them the quickest". It almost nullifies the discharge portion of the lifecycle test. 

[esaj]

7 minutes ago, Jason McNeil said:

Good spot, that would make sense! I wonder what compelled Panasonic to run such an unfavourable test?!  Was it a joke of some bored Panasonic Engineer "Let's put these cells under conditions which will kill them the quickest". It almost nullifies the discharge portion of the lifecycle test. 

Can't say for sure, it would help to compare it with more datasheets from different cells/manufacturers, maybe that kind of "torture test" is some sort of (de facto) standard in the field... at least they aren't giving a too optimistic view of the lifetime?