Locating the C-rating of my batteries

[G Izlude]

Hello folks,

First, let me apologize for posting this in the new member forum, feel free to move it appropriately. I couldn't post to the APV forum yet.

I've been lurking and learning from the forum for some time now. I built a .5 ohm dual coil on a Nimbus rba but I'm reluctant to vape it much untill I have more information about my batteries; specifically, I need the c rating of my EFest 18650 2000 mAh. PBusardo has a great page that gets into the mathematics of determining a battery's max draw, but to use the stated formula, you have to have the C-rating of the battery. I can't seem to find any technical specs for mine that state it's c-rating.

According to Ohm's Law, if I get anywhere close to 3.7v at .5 ohms my battery will need to be able to handle a 7.4 amp draw. As I said above, I'm reluctant to vape from this coil until I have this information. Does anyone know the c-rating for the battery I mentioned above?

Any advice would be appreciated.

 

[DKP#]

According to this page, 10C
Efest IMR18650 2000mAh 3.7V Rechargeable LiMn battery - button top

 

[Baditude]

So, the Efest 18650 IMR 2000 mAh has a 10C Rating, which works out to be a 10 amp continuous discharge rating. Using the Ohm's Law Calculator your 0.5 ohm coil will pull 8.4 amps from a fully charged 4.2v battery, which is within the grey area of a safe margin of safety. Should that coil drop just 0.1 ohm, the amp draw increases to 10.5 amps, which is over it's safe CDR in amps; 0.2 less ohm and it jumps to 14 amps.

Batteries fall in their quality as they age, losing capacity and amp output. You may not notice any trouble while new, but as the batteries age with use the problem will become more severe. Push the batteries a bit further and now you've entered the realm of thermal runaway.

I suggest upgrading to a battery that has more than 10 amp CDR if you wish to continue using sub ohms less than 0.8 ohm (PBusardo's recommendation). Being that these batteries are designed to handle the necessary load their overall expected lifetime in use will be more than a 10 amp battery and have a far wider margin of safety.

AW IMR
18650 1600mah 24A CDR

MNKE IMR
18650 1500mah ​20A

Orbtronic hybrid
18650 SX22 (hybrid) 2000mAh 22A

Sanyo
UR18650EX 2000mAh 20A

Samsung hybrid
INR18650-20R 2000mah 22A

Sony hybrid
us18650vct3 1600mAh 30A
us18650vtc4 2100 mAh 30A

EH IMR
18650 2000 mAh 16A
18650 1500 mAh 22A

Efest IMR
18650 1600mAh 30A

 

[fabricator4]

According to Ohm's Law, if I get anywhere close to 3.7v at .5 ohms my battery will need to be able to handle a 7.4 amp draw. As I said above, I'm reluctant to vape from this coil until I have this information. Does anyone know the c-rating for the battery I mentioned above?

As DKP said, 10C. You have the correct batteries.

You do have to look up the specifications for the battery you are using since it is never printed on the battery cover, and preferably this should be from the manufacturer. This can lead to an error you will see often from people vaping sub ohm, and that is using the peak power rating which is also often listed in the specs.

This rating is meant to cover situations where an inductive load is used, such as electric motors, and anyone who deals with electronics will understand this to mean a transient load, for a few hundred milliseconds maximum.

As a general guideline, IMR batteries usually have a minimum C rating of 5, however you are much better off with the batteries you have as they have a significant safety margin. You also need to keep in mind that the equation relates the C rating to the actual capacity of the batteries, not the theoretical rating. As batteries age the actual capacity may reduce over time.
Discharge Methods

 

[fabricator4]

So, the Efest 18650 IMR 2000 mAh has a 10C Rating, which works out to be a 10 amp continuous discharge rating. Using the Ohm's Law Calculator your 0.5 ohm coil will pull 8.4 amps from a fully charged 4.2v battery, which is within the grey area of a safe margin of safety.

10C at 2000 mAh is 20 amps, not 10?

 

[Baditude]

10C at 2000 mAh is 20 amps, not 10?

I'm currently busy with some other stuff. Yeah my math was off. However, I've had the Efest 18650 IMR 2000mah batteries with a 10 amp CDR, not 20. I'm thinking the true C rating is not 20C, but 10C. I've tried to locate the resources for that info but so far I haven't re-found it. I recall that there was conflicting information when I first researched for the specifications, and once I have some more free time I will try to find it and update in this thread. Sorry for any confusion.


Update: I'm still searching for the C rating for the 18650 Efest 2000mAh IMR battery. I did find one source here on ECF that says it is a 5C with a 10 amp CDR here: http://www.e-cigarette-forum.com/forum/inter-vet-tech-questions/482459-amp-limits.html#post11083810. But I'll continue to try to find more sources.



2nd Update: Another source says this battery has a 10 amp CDR. Efest IMR 2000mAh 3.7v 18650 Battery


After 30 minutes of Google search results, I found no consistancy in the C rating or cont. discharge rating. 90% of the vendors offered no specifications of any help. Even Efest's company page offered no help in specifications. I found more sources that say it has only a 10 amp CDR than I did 20 amp.

 

[fabricator4]

Another source says this has a 10 amp CDR. AW IMR 18650 2000mah Battery

After 30 minutes of Google search results, I found no consistancy in the C rating or cont. discharge rating. 90% of the vendors offered no specifications of any help. Even Efest's company page offered no help in specifications.

I think these are the usual Panasonic cells, 10C. I tend to also think that the 10A rating is a typo or someone not understanding the spec.

These cells do not actually have a very good discharge curve at over 5A. The voltage drops quite quickly and the efficiency suffers. They still have greater capacity compared to the 1600 mAh cells from both AW and Efest, but voltage may sag quite quickly. Probably not a lot in it - the decision would come down to price and suitability as much as the overall capacity.

It's very difficult to figure out what cells are really under the wrapper sometimes - quite often AW and Efest are the same Panasonics (eg IMR 2250mAh) but they give slightly different specifications, including C rating. AW I think claim *all* their IMR cells are Panasonic, Efest quite often are but they leave you guessing.

 

[G Izlude]

thanks for all the help. My fear was that I could potentially be holding a pipe bomb in my hand at such a low resistance. While I'm confident I can safely vape at .5 ohms, I think I'll invest is some slightly better batteries before I fire them a lot. On the plus side, with as much watage as i'm producing, it only takes 2 or three toots to get more than enough nic in me.

 

[DaveP]

I can't help but equate sub ohm vaping with driving a car at 40mph over the speed limit.

If PG and VG are irritants at normally accepted vaping levels, what happens after ten years of vaping room filling clouds? I don't think my lungs are up to the challenge.

 

[Baditude]

I think these are the usual Panasonic cells, 10C. I tend to also think that the 10A rating is a typo or someone not understanding the spec.

It's very difficult to figure out what cells are really under the wrapper sometimes - quite often AW and Efest are the same Panasonics (eg IMR 2250mAh) but they give slightly different specifications, including C rating. AW I think claim *all* their IMR cells are Panasonic, Efest quite often are but they leave you guessing.

I'm starting to doubt whether the IMR cells by AW and Efest are actually re-wrapped Panasonics. AW IMR's say "Made in China" on the battery. The protected ICR AW's say "Assembled in China - cell and IC made in Japan".

I do believe AW's protected ICR batteries are re-wrapped Panasonics. However, Panasonic does not make 19490 or 19350 size IMR batteries, just 18650. My guess is AW has their IMR batteries made in China. Think about it...what Japanese battery manufacturers make or sell 18350 or 18490 IMR or hybrid batteries under their own name brand?

 

[fabricator4]

I'm starting to doubt whether the IMR cells by AW and Efest are actually re-wrapped Panasonics. AW IMR's say "Made in China" on the battery. The protected ICR AW's say "Assembled in China - cell and IC made in Japan".

I do believe AW's protected ICR batteries are re-wrapped Panasonics. However, Panasonic does not make 19490 or 19350 size IMR batteries, just 18650. My guess is AW has their IMR batteries made in China. Think about it...what Japanese battery manufacturers make or sell 18350 or 18490 IMR or hybrid batteries under their own name brand?

You could be right. Investigations seem to indicate that Panasonic is investing heavily in the Hybrid technologies. I always run into a brick wall when trying to investigate IMR technologies from Panasonic. Just another myth, maybe? I know I've been over the data available from Panasonic three times and it never made any sense at all until you point out that possibility.

So where does that leave us? People will say that AW's IMR batteries are the best because they are Panasonic's. I can't find any evidence that this is the case.

 

[fabricator4]

thanks for all the help. My fear was that I could potentially be holding a pipe bomb in my hand at such a low resistance. While I'm confident I can safely vape at .5 ohms, I think I'll invest is some slightly better batteries before I fire them a lot. On the plus side, with as much watage as i'm producing, it only takes 2 or three toots to get more than enough nic in me.

All of the IMR batteries are *relatively* safe. This technology can still fail, but does so at much lower temperature, with no flame, and with much less toxic output. As long as there are vent holes in the mod tube to allow expanding gasses to escape it is safe. I wouldn't like to be around one in full failure mode in a confined space, but even this is less likely due to the lower temperatures involved.

Apart from this, the main contributor to safety is common sense - if the mod (switch, batteries etc) is getting very warm, then it warrants investigation.

 

[chemxsol]

I just got this EFest 18650 2000 mAh 3.7v battery and I was wondering the max amp this battery can pull. I've dug up as much as I could and some places say 20amp and others say 10amp. Seems to me however I found more 10amp listings than 20amp. What do you guys think?

 

[fabricator4]

I just got this EFest 18650 2000 mAh 3.7v battery and I was wondering the max amp this battery can pull. I've dug up as much as I could and some places say 20amp and others say 10amp. Seems to me however I found more 10amp listings than 20amp. What do you guys think?

All of the the V2 batteries are 10C rated. The V1 version was possibly rated at 5C and perhaps the reason for so many web pages that state this battery is only good for 10 amps. Just make sure that you have the V2 batteries.

 

[faulkan]

10C at 2000 mAh is 20 amps, not 10?

I was just fixing to mention that. Glad I saw your post before I did.