Panasonic NCR18650PF

[johnnyz]

Hi everyone

I have a question on a large order of cells I got from NKON. They are the Panasonic NCR18650PF cells..

Heres a pic of them..



I tested about 5 of them and they all came in at about 2580 using my Imax charger . (Charged to full and then discharged to 3 volts at 1 amp. )
Obviously this is less than their rated capacity although the Imax wont go down to 2.75 volts.

Question...are these grade D cells and if so what is the difference between Grade A cells and these. I am also wondering why this is not advertised at NKON before one buys large quantities.

Thanks

John

 

[Jon NCal]

The cells are probably performing in spec. Note several factors: Temp is important, for example at 20 deg. C the nominal capacity is 2750mah, vs 25 deg. C. Discharge rate is important, discharge at a standard rate, ie .2C, 1C etc. so you can compare to the rated capacity on graph. End voltage is important, cell capacity is rated from 4.2v down to 2.5v, look at the published discharge graphs to determine where your discharge curve for your C rate crosses the 3.0v line. Also, charge is important, cut off at 50ma.

 

[Pajda]

Agree with Jon. Your cells seems fine, the problem is in your cell testing procedure. Anyway I have a bunch of NCR18650PF from NKON too for cycle life tests and they are exactly in specified range. They all do >2,850 mAh at 0,2C down to 2,5V.

 

[johnnyz]

Agree with Jon. Your cells seems fine, the problem is in your cell testing procedure. Anyway I have a bunch of NCR18650PF from NKON too for cycle life tests and they are exactly in specified range. They all do >2,850 mAh at 0,2C down to 2,5V.

Do you have a picture of them?..Every picture I saw of these cells they had either a "C" or "D"on them. Was wondering if there is any difference between these and "A" cells...

Yes, I tested another cell and got 2550 at 3 volts(on the Imax) although the actual cell voltage was 3.24 volts...so I think if they were pushed to 2.5 volts they would show another 300 mah of capacity.


John

 

[redilast]

I don't think the big letters of A, B, C, D, E etc is an indication of the grade of the cell. I think its probably maybe the factory that made it or some other production related code.

I know the other numbers at the bottom are the date code. Yours was made 2016-06-25.

As others have mentioned the cells are probably fine and its just the way you are testing it. Temperature must be 25C, charge voltage 4.20v with 50mA cutoff. Discharged down to 2.50v. 0.2C discharge current which is 580mA.

To get closer results you could try the following:

1) Warm up the cell a bit and or make sure temperatures are 25C+

2) Charging at a lower current such as 500mA, many hobby chargers will have a C/10 cutoff, so this may lead to a more full charge with the 50mA cut off.

3) Secondly, to get around the 2.75v voltage cutoff limitation, change it to Ni-Mh 2s discharge. Then the charger will use probably a 2v cutoff, but you can manually check it when it gets low and try to stop the discharge at close to 2.50v.

4) Decrease your discharge current if possible to the recommended 580mA or 600mA would be fine.

5) Also keep in mind that some of these cheaper hobby chargers can have some pretty poor tolerances. I had a cheap turnigy charger back in the day that had its current reading off by a full 10%. You can check the current and voltages and compare with a multimeter. The voltages can be calibrated, the current probably not, but you can just use math to account for the % error.

 

[johnnyz]

I don't think the big letters of A, B, C, D, E etc is an indication of the grade of the cell. I think its probably maybe the factory that made it or some other production related code.

I know the other numbers at the bottom are the date code. Yours was made 2016-06-25.

As others have mentioned the cells are probably fine and its just the way you are testing it. Temperature must be 25C, charge voltage 4.20v with 50mA cutoff. Discharged down to 2.50v. 0.2C discharge current which is 580mA.

To get closer results you could try the following:

1) Warm up the cell a bit and or make sure temperatures are 25C+

2) Charging at a lower current such as 500mA, many hobby chargers will have a C/10 cutoff, so this may lead to a more full charge with the 50mA cut off.

3) Secondly, to get around the 2.75v voltage cutoff limitation, change it to Ni-Mh 2s discharge. Then the charger will use probably a 2v cutoff, but you can manually check it when it gets low and try to stop the discharge at close to 2.50v.

4) Decrease your discharge current if possible to the recommended 580mA or 600mA would be fine.

5) Also keep in mind that some of these cheaper hobby chargers can have some pretty poor tolerances. I had a cheap turnigy charger back in the day that had its current reading off by a full 10%. You can check the current and voltages and compare with a multimeter. The voltages can be calibrated, the current probably not, but you can just use math to account for the % error.

Thanks for the response..

Perhaps you are right..I am going to try this technique and see what happens..I did notice that throughout the test, the reading on my mulitmeter was consistently .11 volts higher than what the reading was on the imax..so when I had the cell reading 3.6 volts it was actually 3.71 volts.

Results of latest test..1 amp discharge temperature at 20 degrees and charged at 1 amp to 4.2 volts.

3.86 volts used 186 mah
3.81 v u 306 mah
3.74 v u 450 mah
3.65 v u 663 mah
3.43 v u 1409 mah
3.39 v u 1620 mah
3.27 v u 2077 mah
3.16 v u 2316 mah
3.01 v u 2535 mah

And at this point the Imax terminated the discharge..however I measured the cell at 3.13 volts.

I will try this test again, but with the following procedures..
temperature of 25 degrees
charge amperage of .5 amp
and use .6 amp discharge to 2.5 volts using the Ni-Mh 2s setting and keep and eye when it gets to 3 volts and will report back my results.

John

 

[Pajda]

My NCR18650PF cells are marked DAV 6527

 

[The Battery Doctor]

The capacity should med tested at 430mA which is mentioned in the datasheet. I always test at 500mAh to get the most accurate capacity. Higher amp = less capacity, since capacity is lost in heat.

Also use a geniune imax (Sky RC), a big problem with the fake ones are that the capacity and voltage results are a bit off so they are useless for testing, the same goes for opus.