A123 26650 M1B Pictures

[countermeasure]

Comparing M1A and M1B battery cells.
M1B was purchased from batteryspace.com.
M1A is from ES for sale forum, disassembled 3s pack with BMS removed.

In the pictures, M1B has the trash can symbol.
The bar codes are a bit different.
The last picture shows two M1B cells. The shrink wrap are different between the two cells.

 

[countermeasure]

M1A and M1B specification sheet

 

[countermeasure]

Different M1 cell grades
*Only applies to M1A, 2.3 AH

Lot number code
FHYYMMXXX-G
F: Cylinder cell
H: Plant
YY: Production year
MM: Production month
XXX: Production day
G:Capacity

Grade “P” 2400 ≤ tested capacity mAh
Grade “R” 2300 ≤ tested capacity < 2400 mAh
Grade “T” 2200 ≤ tested capacity < 2300 mAh
Grade “V” 2100 ≤ tested capacity < 2200 mAh
Grade “X ”0000 ≤ tested capacity < 2100 mAh

 

[countermeasure]

Got a chance to play with the M1B. Room temp is 64 F according to thermostat.

Charged up first. And then immediate discharge, result is 2497 mAH.

Just want to point out that the Turnigy charger volt meter isn't accurate. Will try more charge-discharge tests once I get a Powerlab 6.

 

[countermeasure]

For kicks, here is an M1A discharge test. Same room temp as above. Only got 2208 mAH, not the 2300 mAH nominal.

I will verify again when I get a Powerlab 6.

 

[Doctorbass]

Capacity depend on the C rate you discharged them.

Ex, i have 320x M1A(2300mAh) cells from slavaged deffective or problematic Dewalt pack all made between from 2006 to 2010 and i measured EACH SINGLE CELLS individually in RI and Capacity with accurate measurement device. These cells will be on my 2nd Extra range battery pack on my Zero 2011.


Here is what i got for the average results for these 320 old used cells:

2.201mAh at 20A LVC set to 2.0V
Ri average is 7.41miliohm at 50% SOC at 20.5 degree C

Believe me, these results worth gold ! .. The days i spend measuring them to match them in my battery pack really worth!

Doc

 

[SamTexas]

M1A is from ES for sale forum, disassembled 3s pack with BMS removed.

For kicks, here is an M1A discharge test. Same room temp as above. Only got 2208 mAH, not the 2300 mAH nominal.

Thanks for the report. That's very disappointing, considering it was only discharged at 2.2C.
However, looking at the picture you posted, I noted the missing balance wires. Looks like you were only using the two main lead wires. Unless of course the two balance (or sense) wires are parts of the main wires.

Can you repeat the test? This time at 5C or above if possible and make sure that you use the balance wires as well to see the true battery voltage (and not the battery voltage - the voltage drop across the main leads).

 

[dogman dan]

Hey, at least it could discharge at 2c.

 

[etriker]

M1 discharged at 10amps to 2.5v. After discharge stopped voltage settled to about 3v.

Random cell picked from pile bought from ES seller. http://endless-sphere.com/forums/viewtopic.php?f=31&t=36589

The leads were clipped on those thin little tabs and that is not ideal for higher current tests.

The clips on the Hyperion 1420 get warm at 10a. I hooked up the balance leads for this test.

These cells are useful for about 2ah without overdischarging the cell off the cliff ?

 

[SamTexas]

Discharged at 10amps to 2.5v. After discharge stopped voltage settled to about 3v.

Random cell picked from pile bought from ES seller. http://endless-sphere.com/forums/viewtopic.php?f=31&t=36589

Thank you etriker, I appreciate the data.
But you stopped at 2.5V. The specs says 2.0V. So it's possible that you would actually get 2.3Ah if discharged to 2.0V.

 

[etriker]

That is about what they will do tested on the Hyperion. I have tested many from Dewalt packs too and that is about what they will do.

The newest A123 m1 cell I have seen was made in 2010.

I can't discharge cells off the cliff past 2.5v or so. I just can't ! Not even my rugged A123 cells !

 

[countermeasure]

However, looking at the picture you posted, I noted the missing balance wires. Looks like you were only using the two main lead wires. Unless of course the two balance (or sense) wires are parts of the main wires.

Can you repeat the test? This time at 5C or above if possible and make sure that you use the balance wires as well to see the true battery voltage (and not the battery voltage - the voltage drop across the main leads).

Good suggestion. I went back and studied the charger's manual, in this case the Turnigy Accucell 8150. There is no mention of using the balance wire as part of the 1S test discharge. I figured since it's just one cell, two wires is enough for this particular charger.

The M1B was also discharged without balancing wiring hooked up. Just the main "output" wiring.

The Turnigy charger's max discharge rate is 5 A. I'll report back with more info later.

 

[SamTexas]

There is no mention of using the balance wire as part of the 1S test discharge.

Whether the charger supports sense wires or not is an issue of the charger itself. When doing capacity test, the voltage should always be measured at the battery terminals (which is identical to measuring the voltage with the sense wires.) If a charger does not support sense wires then that charger can never accurately determine the capacity of a battery. That's because regardless of how thick or short the main wires are, there will always be some voltage drop.

 

[countermeasure]

OK. Got my powerlab 6 charger. Power source is 12 V, 14 Amp Pyramid DC power supply used for audio amplifier.
Room temp at 65 F. Charge at 8 Amp. Discharge at 2.25 Amp, or 1C.
1S M1A cell discharge. Cell from ES for sell forum. Disassembled from 3S pack.
I don't have the balancing wire connectors to fit the balancing board, once I chase that component down, I'll be able to plot the internal resistance value.

One thing I observed with the cell, is that once the M1A cell warmed up a bit after the initial cycle, it will deliver more capacity. The third charge-discharge graph with multiple curves, is discharged at 4.75 A rate.

Forgot to mention, I am running Windows XP in VM Ware virtual machine, on MacBook Pro, 10.6 snow leopard.

 

[arkmundi]

Thanks for the thread posts. Know its a year old, but I just built an A123 26650M1B 12S8P battery pack and am interested in doing analytics on it. Hence, those fancy graphs and datasets you've shown. What equipment would I need to do that?