Sub Ohm Coils

[Covert]

I'm not new to electricity by any means, but am seriously left wondering how dangerous or if I am just worrying to much about running a say 0.4 ohm coil with a imr that has a max C rating of 8C which I believe can only handle a constant draw of 8 amps. At 4.1v on a 0.4ohm coil is cranking out 10.25 amp draw on a battery that can only withstand 8 amps max. My logic says I shouldn't be doing this as it could lead to some not to great outcomes, but since I am not majoring in electrical engineering I simply don't have the knowledge to say that my assumption is correct or not. Can anyone clairify for me?

 

[bapgood]

First....I don't know the answer....Are you actually doing it?

I only question in curiosity into how the "protection" is working on that type of cell....thinking the protection circuit should kick in....???

 

[Judge Dredd]

I'm not new to electricity by any means, but am seriously left wondering how dangerous or if I am just worrying to much about running a say 0.4 ohm coil with a imr that has a max C rating of 8C which I believe can only handle a constant draw of 8 amps. At 4.1v on a 0.4ohm coil is cranking out 10.25 amp draw on a battery that can only withstand 8 amps max. My logic says I shouldn't be doing this as it could lead to some not to great outcomes, but since I am not majoring in electrical engineering I simply don't have the knowledge to say that my assumption is correct or not. Can anyone clairify for me?

I don't have that major either, so I am just going to go out on a limb with this, but I would ASSUME that the boost circuit is what regulates current and allows the battery to produce that kind of current when the max is only xC.

 

[Covert]

Bap a very good friend of mine is and i'm just looking out for his well being as well as anyone else that is looking into messing with sub ohm coils. I myself won't go below 0.5 ohms, but i'm also using the Panasonic Hybrids that can pump out 10 amps continuosly and have done my math and am not pushing any known limits. All circuits are being run unprotected with coils that have been metered on a Fluke before usage on mechanical mods.

 

[BJ43]

listen to your logic, it seems to be wise.....

I'm not new to electricity by any means, but am seriously left wondering how dangerous or if I am just worrying to much about running a say 0.4 ohm coil with a imr that has a max C rating of 8C which I believe can only handle a constant draw of 8 amps. At 4.1v on a 0.4ohm coil is cranking out 10.25 amp draw on a battery that can only withstand 8 amps max. My logic says I shouldn't be doing this as it could lead to some not to great outcomes, but since I am not majoring in electrical engineering I simply don't have the knowledge to say that my assumption is correct or not. Can anyone clairify for me?

 

[bapgood]

Bap a very good friend of mine is and i'm just looking out for his well being as well as anyone else that is looking into messing with sub ohm coils. I myself won't go below 0.5 ohms, but i'm also using the Panasonic Hybrids that can pump out 10 amps continuosly and have done my math and am not pushing any known limits. All circuits are being run unprotected with coils that have been metered on a Fluke before usage on mechanical mods.

Gotcha....I forget that all the IMR type cells aren't protected.....good luck to your friend....its out of my realm but doesn't sound extremely safe.

 

[Covert]

Thanks BJ43 My logic is usually pretty spot on, but I don't want to make a big deal out of something that I cannot say with 100% certainty is true or not. I also believe that this is a subject that really should be addressed before something bad happens, there are alot of new people that are getting ahold of RDA's and RBA's and wrapping without owning a meter or having any knowledge of electricity.

 

[LucentShadow]

All definitions of C ratings that I have seen state that the battery's capacity rating (mah) times the C rating can be discharged for an hour divided by the C rating.

So, If you have a 2500mah battery with an 8C rating, then it could provide 2.5A for an hour, or 20A for 7.5 minutes at maximum capability. Personally, I would not put any faith in those ratings being correct. Even if the battery seller is not being overtly dishonest, it's unlikely that the batteries would perform ideally in all circumstances.

If there is any circuitry between the battery and atomizer, it could also be at risk. I doubt that there is, as I've never seen any designed for that level of current.

I'm mostly curious how one sets up an atty to keep up with a 42 watt vape. I can only imagine that acrid dry hits are frequent, but I don't think anyone has airways of iron, so apparently this person has mastered liquid delivery.

IMO, it all seems to be an unhealthy (perhaps obsessive) pursuit of a bigger vape. If so, I could see them trying to push even farther.

Good luck.

 

[WillyB]

Bap a very good friend of mine is and i'm just looking out for his well being as well as anyone else that is looking into messing with sub ohm coils. I myself won't go below 0.5 ohms, but i'm also using the Panasonic Hybrids that can pump out 10 amps continuosly and have done my math and am not pushing any known limits. All circuits are being run unprotected with coils that have been metered on a Fluke before usage on mechanical mods.

First off we have been been exceeding a battery's max discharge rating pretty much from day one with our mods on this forum when 14500s were the most used cells.

If you are really concerned just get a true IMR like the AW18650 1600mAh, not a pretend one like the Panasonic.

 

[cricque]

I've been reading up on these sub ohm coils and twisted 32 awg coils etc. So as I understand it is best to use AW IMR ones. The protected AW ones will not work anyway if you go really low ?

 

[Covert]

(WillyB I haven't been vaping long enough to deal with 14500's been in the 18000 range since I started.) So basically it's not really a problem. I know battery stats from mfgs aren't really correct I was just throwing it out to get a feel if the math I was doing was correct. And LucentShadow I hear you on the delivery system he's got a nimbus with dual coils when he pulls off the top cap it looks like a pile of silica lol. It was not my intent on getting into a deep battery discussion just wanted to see if running sub ohm coils past the max discharge rate of the cell could cause a potential problem and it looks as if it's not a big deal so I leave well enough alone : )

 

[DrMA]

My experience comes from RC, where huge drain currents pushing the limits of batteries are the norm rather than the exception. Pulling more current than the batteries are rated for will make them get warm and drop voltage excessively under load. The temperature problem is not a big issue in vaping since most hits are under 10sec. Even if you take 5-6 hits in a row, the battery still gets a break before it gets hot enough to be of concern. LiPo's will however suffer decreased service life (accelerating increase in internal resistance) when you abuse them like this, so be prepared to replace yours often.

A much bigger problem is that the voltage might drop below safe levels (generally thought to be 3.0V for a typical LiPo) under load, which will rapidly cause irreversible damage to the battery. Frequent excursions below 3.0V are also potentially dangerous and may result in the LiPo's puffing or venting explosively.