Test/review of Molicel INR21700-P42A 4200mAh (Gray)

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ggf31416
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The 14.8A measurement is using some specific cell, with a cell with lower IR – internal resistance – (less voltage sag) it will be something like 18A, with higher IR it will be like 12A to throw random numbers. A cell with higher CDR typically has lower IR but IR isn’t the only factor that determines the CDR.

The Continuous Discharge Rating is the maximum amount of current that can be draw continuously from the cell while keeping sag,temperature, etc. within specs with some added safety margin. The CDR number is only as trustworthy as the the manufacturer, bad brands have vastly inflated or just fake CDR. Drawing higher current than the CDR is possible but unsafe.

Current is loaded battery voltage / circuit resistance or equivalently unloaded battery voltage over (circuit resistance + IR). Many circuits either actively draw constant current or have constant resistance, so current is often oversimplified as being ‘pulled’ in introductory explanations. LEDs actually decrease the resistance as voltage increases as shown by the shape of the Vf curve, so a battery with lower voltage sag may result in a large increase in current.

Agro
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No, you can’t assume that.
1. Amp rating is not really a property of battery but of how its marketed. It is meant to somewhat correspond with battery internal resistance. And it often does with good brands, but that’s not always the case and furthermore it’s often rounded, sometimes up sometimes down. It is normal for a cell to have different amp ratings on different wraps. It is normal to have small capacity differences as well.
2. Basically (in a FET light):
battery_voltage – voltage_sag = led_forward_voltage – current * host_resistance
with voltage_sag = internal_resistance * current
It is not that the light draws 14.8A. First, it draws this number only at certain battery voltage (likely 4.2V). As battery discharges, current draw goes down.
Second, lower battery internal resistance means higher current draw. So in our hypothetical case, the more powerful battery will draw more current.
3. Voltage sag affects runtime as well
4. Thermal stepdown occurs due to heat accumulating in the host. More power draw = faster heat production = faster heat accumulation. The more powerful cell the faster stepdown. There is no cell stress related to that, though some lights don’t work properly with too weak cells (Acebeam EC65 with the stock cell).
5. You can use protected cells but:

  • the protection circuit adds resistance, reducing power draw
  • as you noted there are sometimes issues with the size increase
  • sometimes the circuit trips at high discharge, though in theory it shouldn’t here
  • Acebeam 5100 has fake capacity and fake current rating, IDK if the protection circuit will trip but the cell can’t sustain 20A

JasonWW
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It should also be noted that this Molicel P42A’s 45A continuous rating is merely the factory rating and it’s a bit unspecific.

HKJ does not seem to mention what he thinks the max continuous is. He tests it at 30A and it seems to pass his tests.

Mooch has rated it at 30A continuous and 40A if you monitor the temperature to not exceed 75°C.

Mooch wrote:
The datasheet for the P42A lists 45A as the max continuous current rating but notes that cycle life is reduced at high current levels. Running this cell continuously at 45A gets it much too hot for that to be a continuous current rating we can use for comparing to other cells.

I am rating this Molicel at 30A continuous with a temperature-limited rating of 40A as long as you stop before the cell reaches 75°C.

This still puts it a notch better than the Samsung 40T.

Mooch wrote:
I am estimating the 40T ratings to be 25A with a temperature-limited rating of 35A (if kept below 80°C) and 4000mAh.

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andygold
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So basically for my needs, this Molicel battery should give much better than average performance in this particular light.  My second choice would probably be the Shockli 4550 22A/30A which HKJ rates pretty well too.

Surefire 8X, Lummi Wee, Lummi Raw, Tank007 E09, On The Road M3, Nitecore Tube, Nitecore TINI, Utorch UT01 (cool and neutral), 9V Cube Light, various 3xAAA COB lights, Eternalight, Jetbeam SF-R26, Astrolux EC01

JasonWW
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andygold wrote:

So basically for my needs, this Molicel battery should give much better than average performance in this particular light.  My second choice would probably be the Shockli 4550 22A/30A which HKJ rates pretty well too.


Molicel P42A is one of the best. It’s fairly new as well. The Shockli is also pretty new. It trades a bit of amperage for more capacity. I’m not sure who makes the cell under the Shockli wrapper, but it seems good.

Just to give a bit more understanding, if we look at cells made around the same time, like in the last 2-3 years, you can expect the newest, most efficient chemical mixes. This usually means better performance in at least a couple of areas compared to cells designed 4 or 5 years ago. The chemistry always improves with time.

When we have fairly new cells the manufacturers can do the chemical mix to give certain characteristics. If we look at Samsung, they have the 30T, the 40T and the 50E. The 30T is designed to give the highest output (35A) at the expense of capacity (3000mah). The 50E has the highest capacity (5000mah) at the expense of a lower amperage (10A). The 40T (4000mah) is a middle ground that is a good mix of both, (25A). This is generally true when looking at cells from the same manufacturer and about the same age.

So you notice the Shockli 4550mah is a bit higher capacity than 40T and P42A, but a bit lower in cont. amperage. Plus it’s a 2018 cell, so pretty new. I’m thinking it must be made by a pretty good company to have specs that are close to Samsung and Molicel.

Looking around, it seems the Shockli 4550mah might be a Lishen LR2170SF under the wrapper. That’s a good Chinese brand and probably available for less cost than the P42A and 40T.

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andygold
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Thank you all!!!  I now have a somewhat better understanding of the high-drain cells. 

Surefire 8X, Lummi Wee, Lummi Raw, Tank007 E09, On The Road M3, Nitecore Tube, Nitecore TINI, Utorch UT01 (cool and neutral), 9V Cube Light, various 3xAAA COB lights, Eternalight, Jetbeam SF-R26, Astrolux EC01

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andygold wrote:

Thank you all!!!  I now have a somewhat better understanding of the high-drain cells. 


Now when you start dealing with non-FET drivers, things are a bit different. All the other driver types (Buck, Boost, etc…) will have a fixed current, like 3A, 5A, etc… and then most of what you learned above is not really important. Those are more influenced by voltage sag which we didn’t really get into. Ha ha. Always more to learn. Luckily, you can learn a lot on this forum.

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ClaudioNC
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After charged my eight Molicel 21700 P42A batteries the first time after received them, at 1Ah with VariCore V40 charger, they result to have, more or less 3900mAh, so a little less of the minimum wrote on the specs. 

From 3881 to 3976mAh, with almost all the other units that are more close to the 3900mAh. 

I have not understood if and how is possible to attach pictures in this forum, the 'Insert/edit image' function is not clear to me on what is used for... 

JaredM
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Was this charge capacity or discharge capacity? If this is the charge capacity of their first charge as recieved, then there is nothing to worry about. They come with some percentage of charge already in them.

ClaudioNC
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Is the result of the automatic cycle, doing first of all the full charging to 4.20V and after that the discharging-recharging cycle inside which the capacity value is measured and displayed.

A completly automatic function activable on request of that charger/analyzer. 

JasonWW
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ClaudioNC wrote:

After charged my eight Molicel 21700 P42A batteries the first time after received them, at 1Ah with VariCore V40 charger, they result to have, more or less 3900mAh, so a little less of the minimum wrote on the specs. 


From 3881 to 3976mAh, with almost all the other units that are more close to the 3900mAh. 


I have not understood if and how is possible to attach pictures in this forum, the ‘Insert/edit image’ function is not clear to me on what is used for… 


Please understand that a regular battery charger is not accurate for measuring capacity. The manufacturer and people like HKJ and Mooch have special testing setups that are more accurate.

On top of that, the cells don’t have a single capacity, but more a range. The P42A has a range of 4,000-4,200 mah as measured by the factory.

Small variables in the testing also effect the capacity results. Such as discharge and charge rate and the discharge voltage the charger uses.

The readings you got from your charger seem perfectly normal.

To post pictures you need to have a website you can upload them to and host them. I use Imgur, but there are others. Then you use the link the host provides and you copy/paste it here.

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JaredM
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One of the larger issues with the analytical chargers is the lack of a 4 point connection. This means that any resistance from the rails, internal, and external contacts are not compensated for. At 1Amp, this could result in noticeably premature termination of both charge and discharge cycles. As Jason mentioned, these are decent approximation tools and if cared for and used carefully, can be a way to track the relative health of a cell over time. ‘Careful use’ means things like keeping track of which bay a measurement was taken, and also that the contacts remain clean and cells are installed precisely to minimize contact resistance.

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These should work really well in the NSX3!

Doug S.

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Don’t remember the exact number but my P42A measured about 4030mah with the Lii-500 NOR TEST.

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Hello everyone!!
I´m Álvaro and i wanted to ask all of you an issue that i hope you could help me.
My doubt comes when i have to choose between 2 batteries for my Lumintop fw21 pro. This flashlight offers lots of lumens and the best battery you can choose, is the Samsung 21700 30T. But i find that this battery isn´t big enough for me (3000 mah) and i wanted to buy another battery which could offer me more capacity but keeping the highest ouptut possible. I am between the Samsung 21700 40T and the Molicell 21700 P42A, both have 4000 mah but i read that with the Molicell you get more mah than with the Samsung. I read that is better the first one than the second one. I´ve seen too that with the samsung you get higher voltage at the beginning of the discharge (4.2v-3.9v). At 3,9v they output the same voltage and at this point is where some people say that it´s better the Molicell because it offers a little more capacity. ¿What battery do you recommend me for my flashlight?
I hope i´ve explained it as well as i could.
Thank you.

JasonWW
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Alvaro52021 wrote:
Hello everyone!!
I´m Álvaro and i wanted to ask all of you an issue that i hope you could help me.
My doubt comes when i have to choose between 2 batteries for my Lumintop fw21 pro. This flashlight offers lots of lumens and the best battery you can choose, is the Samsung 21700 30T. But i find that this battery isn´t big enough for me (3000 mah) and i wanted to buy another battery which could offer me more capacity but keeping the highest ouptut possible. I am between the Samsung 21700 40T and the Molicell 21700 P42A, both have 4000 mah but i read that with the Molicell you get more mah than with the Samsung. I read that is better the first one than the second one. I´ve seen too that with the samsung you get higher voltage at the beginning of the discharge (4.2v-3.9v). At 3,9v they output the same voltage and at this point is where some people say that it´s better the Molicell because it offers a little more capacity. ¿What battery do you recommend me for my flashlight?
I hope i´ve explained it as well as i could.
Thank you.

You are over thinking things. The 30T might draw more amps, but you will not SEE any difference in output. You will only measure the difference in output using an integrating sphere. So do not worry about it. The 40T and P42A are both great. Get whichever is cheaper for you.

Texas Ace Lumen Tube and JoshK Sphere calibrated with Maukka lights

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