Top 21700 cells: LG M50 Grade B 5000mAh vs Samsung 48G 4800mAh

thunderheart

thunderheart

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Hi guys! I've tested two high capacity 21700 cells - LG M50 Grade B(5000mAh) and Samsung 48G (4800mAh). The latter i had already tested before and the re-testing of another cell showed almost no difference with previous test results. The M50 is a new cell which is being sold as 10A one, but in its datasheet the maximum discharge current is mentioned as 7.28A. Nevertheless i've also discharged it at 10A to look at it's behavior.

The cells i've bought fromQueen Battery.

As always, I've tested withZKETECH EBC-A20and a self-made battery holder. It's a PC-connected battery tester supporting 4-wire measuring and discharging at up to 20A.
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I've followed all the prescriptions of the IEC61960-2003 standard concerning battery's capacity measurement. Before each discharging cycle each battery was charged at standard current mentioned in its datasheet to charge end voltage (4.2V) (cut-off at 0.1A, which is the lowest supported by EBC-A20). Before each discharging or charging i've held a 1-1.5hrs pause. The environment temperature was about 25C.

LG INR21700 M50 (Grade B)

This cell has absolutely no marking.
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The main specs from itsdatasheet:
Nominal energy:18.20Wh
Minimum energy:17.60Wh
Minimum capacity:4850mAh
Nominal voltage:3.63V
Standard charge current:1.455A
Max. charge current:3.395A
Charge end voltage:4.2V
Charge cut-off current:50mA
Max. discharge current:7.275A
Discharge cut-off voltage:2.5V
Weight (w/o washer):681g

The measured weight is 69.16g.
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Test results:
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Great results - 5104mAh/18.44Wh at 0.2C (0.97A) and almost 5000mAh at 5A! Even at 10A, which is way above the declared maximum (7.28A), the M50's curve looks very nice. I think it's a very capable cell and LG shouldn't limit the discharge current by 7,28A.

Samsung INR21700-48G

This guy is marked as INR21700-48G SAMSUNG SDI M5-1.
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The main specs from itsdatasheet:
Typical energy:17.4Wh
Minimum energy:17.04Wh
Typical capacity:4800mAh
Minimum capacity:4700mAh
Nominal voltage:3.6V
Standard charge current:1.44A
Max. charge current:4.8A
Charge end voltage:4.2V
Charge cut-off current:96mA
Max. discharge current:9.6A
Discharge cut-off voltage:2.5V
Max weight:69g

The measured weight is 67.58g.
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Test results:
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At 0.2C (0.96A) the results are a bit higher than declared. At 5A and 9.6A the 48G showed good results with nice curves.

COMPARISON

At 0.2C.
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Despite the 0.01A difference in discharge current LG M50 showed better result than the 48G. Pay attention to their curves - they are almost the same during the first half and they look very similar during the second half of discharging. This is because they use the same (or almost the same) chemistry.

At 5A.
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The results are very close, thought the M50 is better again.

At 10A/9.6A.
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I've discharged the M50 at 10A and the 48G at its maximum allowed 9.6A. Nevertheless the M50 showed higher capacity and almost the same energy in comparison with 48G.

CONCLUSION

Both cells are surprising with their results, but i liked the M50 a bit more than the 48G. I don't understand why did LG limit the max discharge at 7.28A, because it handles 10A easily. Of course the cycle life won't be the same as at 7.28A, but nobody expects a great cycle life at max rates. There is alsoLG M50 Grade Acell, which was unavailable when i was making the order. Does anybody have any official info about the difference between Grade A and Grade B M50s?

I hope this test was interesting to read/watch and i'll be happy if it was useful for someone:) Here is thevideo versionof this review with size comparison between 18650, 21700 and 26650 cells:

P.S. this is my YouTube channel:www.youtube.com/thunderheartreviewsIt will be highly appreciated if you subscribe:)!
 
Wow. That LG cell is a beast.

It actually has a slightly better capacity to volume ratio compared to the NCR18650GA.
 
The next big thing in 21700 format, if you need more grunt, is the Samsung INR21700-40T. Not sure if it's T at the end. It's a 4000mAh 30A or 40A cell, there is no datasheet available (yet) and some people claim 30A but I believe this might be wrong. But I could be wrong as well so take it with a grain of salt. It's the cell that is supposed to end up in the latest generation of powertool batteries, a spiritual successor to cells like the immensely popular and widely used INR18650-25R and the 20700 cells used before. These 20700 were rated at up to 45A at 3500mAh, that's why I think 30A for a new 4000mAh 21700 cell might be wrong.
 
BTW, right now i'm testing the Samsung INR21700-30T (35A). I'll publish the test as soon as it's ready))
 
Be careful with it.

It's an extremely high drain cell, and if you short it, you could upwards of 300-350A :D

Also, measure its internal resistance if possible.
 
IR for a new cell of this model will be around 20mR, I guess. Its rating is very conservative, it will easily do 30A. It will get warm, but not even close to hot, and has reserves for a complete 40A (and more) discharge.
 
Oh, actually that is really easy, especially with your setup to do it accurately since you have very low resistance contacts.

I am speaking about DC resistance, not AC resistance.

Here is how you do it, with an example:

?V = voltage delta = V-VL
V = cell voltage = 4,2V
VL= Voltage under load = 3,9V
C= current flowing= 2A
IR = Internal resistance of a cell = ?V/C

?V = V- VL = 4,2V-3,9V = 0,3V

IR = ?V/C = 0,3V/2A = 0,150 Ohms = 150 miliOhms.

See? With a very low resistance contact setup, it is really easy to do, and precise.
 
BlueSwordM said:
I am speaking about DC resistance, not AC resistance.
Click to expand...


Thanks for detailed instruction! The thing is that the IR mentioned in datasheets is the AC resistance and to check and compare it with manufacturer's values i should have animpedance meter with AC 1 kHz
 
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