A123 Systems ANR26650 Grade A vs Grade B - discharge test

[thunderheart]

Original article: https://www.thunderheartreviews.com/2018/08/lifepo4-a123-systems-anr26650m1b-grade.html

Hi guys! I've got 4 ANR26650s - 2 of each grade and tested a pair by discharging at 0.5A (0.2C), 5A, 10A and 20A discharge rates. Then i tested the second pair at 20A and compared all 4 cells.

The cells were bought from Queen Battery. The first pair was bought 4 months ago and the second - a month ago.

As always, I've tested with ZKETECH EBC-A20 and a self-made battery holder. It's a PC-connected battery tester supporting 4-wire measuring and discharging at up to 20A.

I upgraded my holder by replacing the steel pads with pure copper ones (20x20x0.3mm)

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 (2.5A) mentioned in the datasheet to 3.6V (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 20-25°C (23-25°C to be honest).

Discharge cut-off voltage is 2.0V for these batteries.

The Grade A cell has more information on its wrapper than the Grade B one which only is marked "ANR26650"

and the Grade B's negative pole has no stripes around the metal

The positive poles are identical

The Grade A's results:

The Grade B's results:

Surprisingly enough, the Grade B cell appears to be slightly better than the Grade A one. So let's compare 2 Grade A cells with 2 Grade Bs at 20A to see if that's a rule or exception

It seems that both of Grade Bs are better than the more expensive Grade As. Two pairs are not enough to conclude a rule, but at least we can see that the Bs are not worse than As, if not better. Maybe they have reduced cycle life or they are worse at higher discharge rates - i don't know and i have no way to check that. The maximum discharge current i can apply is 20A which i did. I hope this test was useful for ES members :wink:

The video version of this review:
[youtube]sESdD4FqXDQ[/youtube]

P.S. this is my YouTube channel: www.youtube.com/thunderheartreviews It will be highly appreciated if you subscribe I need to reach 1000 subscribers to activate monetization and i need your support guys!

 

[Hillhater]

From your results , there looks to be approx a 10-15% difference in the IR between the A and B cells (A being lower).
Maybe that is one of their criteria for grading cells. .?

 

[thunderheart]

You mean they are ranging Grade B higher than Grade A? Maybe... But it seems kinda strange to me...

 

[Pota]

Isent it so that the 26650M1B is the more expensive?
Aint the grade A actualy the M1B, with more info?

 

[thunderheart]

Yes, it is.
The Grade A (M1B) costs US$5.6 and the Grade B - US$4.6

 

[Hillhater]

You mean they are ranging Grade B higher than Grade A? Maybe... But it seems kinda strange to me...

No. The opposite. A grade has a lower IR than the B grade.
Its only marginal 0.0175 Ohm for A grade, vs 0.020 Ohm for the B grade (All appprox figs)
So the A grade is a better cell in respect to IR.
But there may well be other factors in the grading classification.

 

[thunderheart]

But there may well be other factors in the grading classification.

Maybe... Googling was useless so all i can is just suggest

 

[Pota]

Isent M1B like 2500mah and M1A like 2300MAH?

 

[Hillhater]

Isent M1B like 2500mah and M1A like 2300MAH?

Both cells a M1B models.....but different grades of quality .
Look at the output graphs in the first post, ..
Both output 2500 mAh capacity.

 

[liveforphysics]

B grade cells sometimes are slightly higher than expected capacity. Sometimes slightly lower. Most often cells are B grade because something happened that caused a higher than normal self-discharge internal leakage current, which often means they will micro gas inside until premature failure.

 

[Pota]

Im buying a123 anr26650m1b. Grade A.
They say these are the one original.
Is it fake or not?

 

[thunderheart]

Hmmm.... All i can say is that their wrapping differs from my Grade A's

 

[SamRich]

Thanks making those measurements and sharing the results!
Does anyone know what is that opening/hole on the top? A vent?

 

[thunderheart]

Does anyone know what is that opening/hole on the top? A vent?

Should be

 

[ecomax1]

HELLO , i search to made some lifepo4 battery for solar PV in 15S 10P with 90 ah cells
, some cells are grade B some grade A ,price are simple or double
the capacity on test are same , what is differences grade A and B ??? internal resistance ? discharge Rate is limited ? thanks for help

 

[john61ct]

Are you talking about ANR26650s?

 

[jonyjoe303]

from what I seen, internal resistance always determines the better quality cell. The lower the resistance the higher the discharge rate. The high discharge cells always sell at a premium price.

For a powerwall you might not need high discharge cells, but for a bike pack you need to pay the the extra costs for the superior performance.

For A123 cells the difference between A and B is insignificant by the tests done. But the price difference is significant, an extra dollar for no extra benefit, adds up very quickly.

 

[john61ct]

Discharge rate aka power density design (IR) and

Energy density

are opposing goals. Designing for one means compromising on the other.

Neither correlates with reliability / longevity, in a non-propulsion, low C-rate usage context.