LiFePO4: A123 Systems ANR26650M1B Grade A vs Grade B

LiFePO4: A123 Systems ANR26650M1B Grade A vs Grade B - discharge capacity test

I've got 4 ANR26650 M1Bs - 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.

Note: ANR26650M1B cells now are being manufactured and sold under Lithium Werks brand. In March 2018 Lithium Werks acquired A123 Systems' industrial business and manufacturing plants located in Changzhou, China. These plants were the first to introduce the revolutionary NanoPhosphate® technology in the form of cylindrical cells.

Lithium Werks ANR26650M1B Nanophosphate LiFePO4 2.5Ah 8.25Wh 3.3V cell

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 to version 2.0 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 ANR26650M1B datasheet (pdf) 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).

A123 Systems ANR26650M1B has the following specs according to it's datasheet:
Nominal capacity: 2.5Ah at 0.5C rate
Minimum capacity: 2.4Ah at 0.5C rate
Nominal voltage: 3.3V
Charge end voltage: 3.6V
Standard charge current: 2.5A (1C)
Fast charge current: 10A (4C)
Max continuous discharge current: 50A (20C)
Max pulse discharge current (10 sec): 120A (48C)
Discharge cut-off voltage: 2.0V
AC impedance at 1KHz: 6mΩ
Weight: 76g

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

A123 Systems ANR26650M1B Grade A capacity test results:

A123 Systems ANR26650M1B Grade B capacity test 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 or some of them have scratches on the barrel - i don't know.

I've made the video version of this review. Watch it on YouTube.

Check out my YouTube channel for batteries, chargers and other stuff reviews.

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