Results of tests from two orders of 12 Molicel P26A (24 total) high amp cells

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fogus
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Results of tests from two orders of 12 Molicel P26A (24 total) high amp cells

Abstract

Measurement results taken from 24 Molicel P26A cells are shared with the goal of eliciting feedback from the community. 12 cells were purchased from 18650batterystore.com near the end of April 2021 and 12 cells were purchased from imrbatteries.com at the beginning of May 2021.

Cells from both sellers were inscribed with “INR-18650-P26A” on the first line and “+ MOLICEL 087” at the beginning of the second line.

The cells from 18650batterystore.com were also inscribed with “2KB03 08” at the end of the second line, and the cells from imrbatteries.com were inscribed with “2KA01 01” at the end of the second line.

Methods

The cells were run through the standard automatic capacity test on the Vapecell S4 Plus charger. Cell capacity and mOhm rating was noted on each cell after the completion of the test. The cells were also weighed. The cells were tested in a room at ~21C with a 120mm computer fan blowing slightly across them (dialed down by a PWM chip).

Results

Results for each cell are listed below. An X is marked next to each cell which is under spec for internal resistance (20mOhm max). Additional X marks are shown for each 10mOhm deviation from spec. The cells weighed ~46 grams (within the 50g max spec).

18650batterystore.com

  1. 2600mAh, 20mOhm
  2. 2648mAh, 20mOhm
  3. 2631mAh, 23mOhm X
  4. 2676mAh, 34mOhm X
  5. 2721mAh, 21mOhm X
  6. 2658mAh, 21mOhm X
  7. 2671mAh, 21mOhm X
  8. 2621mAh, 25mOhm X
  9. 2631mAh, 25mOhm X
  10. 2573mAh, 32mOhm XX
  11. 2623mAh, 40mOhm XXX
  12. 2660mAh, 51mOhm XXXX

In summary:

  • 2 cells meet spec
  • 7 cells are within 10mOhm of spec
  • 1 cell is within 20mOhm of spec
  • 1 cell is within 30mOhm of spec
  • 1 cell is within 40mOhm of spec

imrbatteries.com:

  1. 2658mAh, 18mOhm
  2. 2627mAh, 18mOhm
  3. 2597mAh, 25mOhm X
  4. 2676mAh, 29mOhm X
  5. 2605mAh, 25mOhm X
  6. 2651mAh, 28mOhm X
  7. 2630mAh, 32mOhm XX
  8. 2631mAh, 32mOhm XX
  9. 2608mAh, 32mOhm XX
  10. 2651mAh, 40mOhm XXX
  11. 2731mAh, 40mOhm XXX
  12. 2629mAh, 43mOhm XXX

In summary:

  • 2 cells meet spec
  • 4 cells are within 10mOhm of spec
  • 3 cells are within 20mOhm of spec
  • 3 cells are within 30mOhm of spec

Discussion

There are several questions for which responses are desired:

  1. How accurate is the Vapccell S4 Plus?
  2. How consistent are mOhm readings over time?
  3. Are these results (in particular, the mOhm rating deviations from specification) typical for new 18650 cells in general? Are they typical for Molicel? Are they typical for the P26A in particular?
  4. How far out of spec would a cell have to be for a reasonable purchaser to return them?
  5. If I re-test these cells, how much should I expect they vary?
  6. Has anyone else experience the Vapecell S4 Plus bug which leaves cells empty after a capacity test? In my testing, this happened about 1/4 of the time (seemed random). When watching the charge after the capacity test had finished the “drain” phase, the cell % would go from 1 to 100 over about 10 seconds(!) (showing every integer from 1 to 100), but the voltage would remain at 3.0V.
  7. What do “2KB03 08” and “2KA01 01” indicate?
  8. What mOhm rating would be concerning for these cells in general use in D4v2 flashlights? At what point in their deterioration (measured by mOhm) over their life should they be retired from high output applications?
JaredM
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Contact resistance is a huge variable not compensated by any tester without a 4 point connection. Cleaning all contacts (cells and charger bays) and installing the cells perfectly aligned is necessary to get the most consistent results. Also, realize each slot may have it’s own systematic error.

A cells IR also varies with SOC and temperature. If there was a way for you to get all cells to a matching ~3.8V or so and measure them all in the same slot 3x each, removing and reinserting is the only way to get data that I’d consider super relevant.

Funtastic
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You did a lot of work, but no charger with an analyzing function for both capacity and resistance is going to accurate.

HKJ notes: “The internal resistance calculation is wrong.”

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Lux-Perpetua
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Better buy a four-point probe impedance meter like Vapcell's YR-1035 or the SM-8124A to measure AC (1kHZ) impedance. This is not the internal resistance (DC) but you still get an idea if there's any variation in shelf life or wear among the tested batteries. A brandnew Molicel P42A should probably be around 8-10 mOhm on the impedance meter.

CR888
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JaredM wrote:
Contact resistance is a huge variable not compensated by any tester without a 4 point connection. Cleaning all contacts (cells and charger bays) and installing the cells perfectly aligned is necessary to get the most consistent results. Also, realize each slot may have it’s own systematic error.

A cells IR also varies with SOC and temperature. If there was a way for you to get all cells to a matching ~3.8V or so and measure them all in the same slot 3x each, removing and reinserting is the only way to get data that I’d consider super relevant.


Interesting you mention this, I notice large differences in resistance no’s between slots on my Nitecore USM4 charger. Like I’ll swap a cell with xxx resistance from slit 1 to slot 4 and get a very different number. This is the same for the ‘charging status’ where the same cell could be rated ‘poor’ in one slot & ‘good’ in another. So I don’t think these sub $50 Chinese chargers can be relied on for quality testing data. Even the voltage (which seems to be most accurate) is nowhere near as accurate as a DMM.

CR888

snakebite
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unless its a good dedicated ir/esr tester the results will be as you posted.
completely random.
my dick smith esr carefully zeroed showed .01 on every one of those cells i got from 18650batterystore.
still a spread from 10 mohms to 19mohms.
but thats its resolution capability.
weeds out fakes and duds.

d_t_a
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Lux-Perpetua wrote:

Better buy a four-point probe impedance meter like Vapcell’s YR-1035 or the SM-8124A to measure AC (1kHZ) impedance. This is not the internal resistance (DC) but you still get an idea if there’s any variation in shelf life or wear among the tested batteries. A brandnew Molicel P42A should probably be around 8-10 mOhm on the impedance meter.

I’m getting around 9mOhms on the P42A with YR1030.

For both P26A and P28A, I get around 12mOhms with YR1030..

Molicell P26A IR:

Molicell P28A IR:

~~~~~~~~

I’ve tested some dubious (non-genuine) “P26A” and they differ in design, weight & IR & capacity test (non-genuine yields only around 2000-2100mAh in capacity with MC3000)

Funtastic
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Didn’t realize there were fakes of Molicel yet, thanks.

Most accurate way to test resistance is charge to 4.20v and let them sit for 30 minutes. This is what Mooch told me to do

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CR888
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Good info dta…wish we had a dedicated thread filled with posts just like yours showing the minute difference between fakes & originals of all brands and cell types. The fakers are shifty fuggers who put out convincing copies.

CR888

vapcell Dennis
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Because of the line resistance and contact resistance, it is difficult for charger to measure the DC internal resistance accurately

S4 plus can measure the capacity as a reference, the difference is within 5%

Consider purchasing vapcell yr1030 to measure AC internal resistance, which is very accurate

thank you

fogus
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Thanks for all the info!

I have ordered https://www.ebay.com/itm/174713161514 (“YR1030+ Lithium Battery Internal Resistance Tester Meter Test Range 0-28V tzt”)

I also re-ran the highest cells through the tester and they all got much better numbers on the second run. For example, the 51 mOhm cell dropped to 26 mOhm.

d_t_a
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fogus wrote:
Thanks for all the info!

I have ordered https://www.ebay.com/itm/174713161514 (“YR1030+ Lithium Battery Internal Resistance Tester Meter Test Range 0-28V tzt”)

I also re-ran the highest cells through the tester and they all got much better numbers on the second run. For example, the 51 mOhm cell dropped to 26 mOhm.

I think the YR1035+ is the latest update…

There are the YR1030 (older), YR1035 (more precision), YR1030+ (newer update of the YR1030) and the YR1035+ (newer update of the YR1035) in Yaorea’s line of AC testers.