Bench Test Results: Molicel P45B - 50A 4500mAh 21700…an extraordinary cell!

CamLight

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As Battery Mooch I tested these cells in January for my Patreon supporters and have been torture testing them along with the Molicel P42A and the Samsung 40T since then. With the release of the Molicel P45B hopefully coming soon it’s finally time to post some test results. The cycle life torture test results will remain patron-only though.

The Molicel P45B is an extraordinary cell, matching or outperforming almost every other round cell I have tested at all current levels. The official word is that it will be available before the end of the year but there have been a couple of rumors that some vendors will have it by Summer. I can’t predict who will have it or when.

Compared to the Molicel P42A, the P45B is supposed to have about 7% more capacity, 22% lower DC internal resistance (DC IR), and a higher charge rate. Its main competitor is supposed to be the Samsung 50S.

In my testing the P45B was a better performer in every way over the Molicel P42A:

  • The P45B had almost 9% higher capacity.
  • The P45B had about 33% lower DC IR (at 100% charge).
  • The P45B’s charge rates are 4.5A standard/13.5A max (70°C cutoff) and the P42A’s are 4.2A standard/8.4A max (60°C cutoff).
  • The P45B had longer run times at all discharge current levels.

The P42A is still a great cell! It’s just that in the four years or so we’ve been using it battery tech has improved and the P45B is a perfect example of that.

Compared to the Samsung 50S…
  • The P45B has about 7%-8% less run time at 5A and 10A.
  • The P45B runs for longer though at about 15A and higher.
  • The P45B has a 26% lower DC IR (at 100% charge).
  • The P45B runs MUCH cooler at moderate to high current levels.
  • The P45B has a higher standard and max charge rating (2.5A/6A for the Samsung 50S).

So while the Samsung 50S had slightly longer run times at 10A or lower, due to its higher capacity, the Molicel P45B beats it in every other way in my opinion. The P45B will easily be my choice for best all-around performing round cell and also my #1 choice for moderate to high power applications.

The preliminary datasheet only lists a “temperature-limited” rating of 50A. Molicel says you can run this cell at 50A but only if it never reaches a temperature of 80°C (hot!).

You cannot run the P45B at 50A continuously until it is empty! This non-continuous rating is set by Molicel for this cell’s intended applications; power tools, electric vacuum cleaners, and similar devices where the cell is used really hard for short periods of time.

While you can run this cell at 50A for a while I recommend staying below about 35A to help reduce voltage sag, improve performance, extend cell life, and reduce risk. Especially if the cells are in a battery pack where they heat each other up. Use a 35A rating for comparing this cell to other cells with true continuous current ratings.

The two cells I tested delivered 4477mAh and 4488mAh. This is great consistency and is typical of cells from the big manufacturers. The cells I tested exceeded Molicel’s 4400mAh minimum capacity rating but didn’t quite meet the 4500mAh “typical” rating. I’m not worried about this at all, especially since it’s only a tiny difference and I tested these cells in January and tweaks to the capacity can be made. I’ll retest these cells once they become widely available.

See the table below for the delivered energy (Wh) and max temperatures the P45B, P42A, and 50S reached in testing.

See my 21700 Ratings and E-Scores table (link below) to see how this cell performed against others.

Four cells were sent to me for testing by N-Power Energy, global distributors for Molicels (https://www.npecell.com). Thank you!

18650 Ratings and E-Scores Table:
https://www.e-cigarette-forum.com/blog-entry/18650-battery-ratings-table.7447/

20700/21700 Ratings and E-Scores Table:
https://www.e-cigarette-forum.com/blog-entry/20700-21700-battery-ratings.7827/

To see how other cells have tested check out this link: https://www.e-cigarette-forum.com/forum/blog-entry/list-of-battery-tests.7436/
 

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Thanks for posting. I had not heard of this cell until now.
 
500 cycles to 80% too. This would make a mean 3p 20S pack in a downtube case if one can be found!
 
can you throw it in the freezer overnight and do a 7.5 amp discharge so we can compare the sag to the p42a and 40t?

https://endless-sphere.com/forums/viewtopic.php?f=14&t=106550&start=25#p1597399
 
Fantastic impedance, thanks for sharing Mooch. I've always appreciated your work.
 
Thank you for posting, and also for listing the discharge max-amps with a temperature qualifier.

May I ask...what method do you use to discharge cells, measure discharge, and measure shell temperature?
 
spinningmagnets said:
May I ask...what method do you use to discharge cells, measure discharge, and measure shell temperature?

For some tests, a pair of BK Precision 8601 Electronic Loads and the temperature sensing described below.

For these tests…calibrated West Mountain Radio CBA Pro IV Battery Analyzer modified for lower voltage drops and better cooling (to reduce thermal drift) with custom high-current mount and supplemented by two CamLight CC-400 electronic loads that I designed (150A/400W continuous each). Discharge current confirmed via 0.25% tolerance current shunt connected to calibrated Fluke 87 V meter.

Temperatures measured via Fluke type-k thermocouple and calibrated Fluke 52 II temperature meter. Thermocouple positioned at halfway point of cell case with Kapton tape, making sure to also tape down against the cell at least 2cm of the thermocouple’s cable to prevent any effect of ambient air on the thermocouple.

Ambient temps always held to 24°C, +/-2°C. (typically +/-0.5°C), cell in the open but still air.
All cells are soaked at that temp for at least two hours before charging. Cells are charged to 4.20V at 1A, down to 100mA, and then left to come to ambient temp for one hour before each discharge test starts.
 
goatman said:
can you throw it in the freezer overnight and do a 7.5 amp discharge so we can compare the sag to the p42a and 40t?

https://endless-sphere.com/forums/viewtopic.php?f=14&t=106550&start=25#p1597399

LOL…having so many problems staying logged in and when posting!
I’m torture cycle life testing a 40T3 for my patrons now but will try to do that freezer test later this week.

To confirm…full charge to 4.20V, soak in freezer at least overnight, and then 7.5A down to 3.2V plotting run time vs voltage and recording max temp and delivered Wh and mAh?
 
CamLight said:
spinningmagnets said:
May I ask...what method do you use to discharge cells, measure discharge, and measure shell temperature?

For some tests, a pair of BK Precision 8601 Electronic Loads and the temperature sensing described below.

For these tests…calibrated West Mountain Radio CBA Pro IV Battery Analyzer modified for lower voltage drops and better cooling (to reduce thermal drift) with custom high-current mount and supplemented by two CamLight CC-400 electronic loads that I designed (150A/400W continuous each). Discharge current confirmed via 0.25% tolerance current shunt connected to calibrated Fluke 87 V meter.

Temperatures measured via Fluke type-k thermocouple and calibrated Fluke 52 II temperature meter. Thermocouple positioned at halfway point of cell case with Kapton tape, making sure to also tape down against the cell at least 2cm of the thermocouple’s cable to prevent any effect of ambient air on the thermocouple.

Ambient temps always held to 24°C, +/-2°C. (typically +/-0.5°C), cell in the open but still air.
All cells are soaked at that temp for at least two hours before charging. Cells are charged to 4.20V at 1A, down to 100mA, and then left to come to ambient temp for one hour before each discharge test starts.

I think you would enjoy visiting our lab an LA next time you're on the west coast, we might have a job for you here. Imagine 2000Amp DC loads, 240Amp EIS capable cycler channels and forced temp control (with the ability to force and maintain programmed temp gradients across the cell while testing). Imagine hard vacuum chamber IR insulated cell test fixtures to enable cell heat capacity and thermal conductivity measurements, including from temp probe arrays embedded down the core of the jellyroll and being re-sealed with the temp sensor leads passing out of the can. Imagine measuring the cell thermal runaway energy and release rate and gas species in the calorimeter. Visit and lets chat about opportunities when you're available.
 
goatman said:
can you throw it in the freezer overnight and do a 7.5 amp discharge so we can compare the sag to the p42a and 40t?
https://endless-sphere.com/forums/viewtopic.php?f=14&t=106550&start=25#p1597399

It did well…

Molicel P45B Cold Cell Discharge Test
- Cell date code 2L830.
- Ambient temperature = 23.6°C.
- Cell charged to 4.20V at 1A down to 100mA cutoff.
- 9.5 hours in a freezer, temp ranged from -15.2°C to -15.6°C (over 6hr period) after cell dropped to freezer temp.
- Cell removed from freezer with gloved hand at -15.5°C., test started within one minute after removing from freezer.
- Freezer spray on cell mount contacts to prevent warming of cell.
- Discharged at 7.5A down to 3.20V, plotted at 4Hz rate, bare cell in open still air.
- Start voltage = 4.143V, initial sag down to about 3.89V
- Temperature at end of discharge = 30.8°C.
- Delivered capacity = 3628mAh.
- Delivered energy = 13.07Wh.
- Run time = 29.06 minutes.

8B3C13AF-976D-4DBF-A926-B32FF6DAEA11.jpeg
 
Great information! Love your work. Any idea regarding the maximum safe current for both Molicel cells for short bursts such as 10 seconds (assuming the continuous current remains close to 35A)? Thanks 👍

Gary
 
Controlling heat build up is the biggest hurdle. Finding active cooling and cell spacing key.

What a great addition to my electric ducted fan radio controlled airplanes! The Molicel-p42a 4200mAh cells have given my jets more than double the flight-times over the typical lithium-polymer chemistry, at half the cost! Yes packs have to be individually assembled, old-school soldering required, but isn't it half the fun.... seeing something come together is rewarding.

These new 45b cells will be even better so I'll be looking for them.

Typically for EDF jets the flight consists of sustained high currents loads in the 20~30C range and battery packs come down quite warm. No way a Li-Ion can handle the loads. Runs are 4~5 minutes with judicious throttle management. Where these Li-Ion chemistry cells really shine are situations where the user wants extended flights at partial throttle, flying around at half-throttle is desired for scale-like maneuvers and a relaxed atmosphere. Here flights can be 5x duration.

When aiming for a sustained load the p42a cells are happiest at @18 amps and lower to keep heat building up over the extended periods. Where real fun begins is being able to find airframes large enough to handle cells in parallel. When suitable platforms are able to hold 4p, 6p bricks the capacity of 16,800mAh and 25,200mAh give sustained loads of 100A easily. A comparable lipo being double the price with only 10% weight savings.

These newer 21700 cells will make a lot of RC users very happy.

DsD Chuck

Typical 3min flight..... 6s5000mAh x2 packs.
https://youtu.be/kKfBpQW2bsw

Mine taking it easy with 50% power for maiden.
6s6p25200mAh
https://youtu.be/MIrr9GiIyWw
 
Hello, I bought 2 cells for testing at nkon but they seem to bee very different at my tests.

Data
Resistance DC at 4,2V.
Energy from 4,2-2,5V, individual discharge profile fluctuating 30-50A, discharge time about 31 min until 2,5V are reached, then only 10A about 2 min until 2,5V are reached again
Temperatur difference is the range from 21°C at start to the end Temperatur

Cell 1
10,5mOhm
14,77Wh
Tdifference 21,3°C

Cell 2
7,69mOhm
15,21Wh
Tdifference 18,1°C

Could someone vaildate this data?
Is it normal for these cells to be so different or did I just get a bad cell?
Thanks
 
You did test the samsung 40t as I had a pack made of 20s 6p pack. And only got 19ah and now 15ah at 50amps. It has blue elephant BT bms. I'm thinking counterfeit cells. As on paper it's 24ah. Always in balance.
I just thought it was the cats mellow the Samsung 40t cell.
2.5 years old
 
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