Vape Science & confusion: Is there a variable missing in Ohm’s law for proper vaping?

[colonel2lucky]

On all vaping websites, they talk about Ohm’s law and the simple P=V^2/R so lower resistances generate higher powers and therefore we will need to vape that lower resistance coil at a higher power. Simple.

So why do some people vape a 0.1 ohm coil at 75W and if they increase the wattage it gives out a burning taste, and others are able to vape it at 100W?

I’m a scientist but a beginner to vaping so is there any equation out there that would better reflect all the parameters involved (such as the equation behind the steam engine calculator)?

If you have the time, this concept is also making me confused in these specific examples. Can you figure out the answers?

1. Can I build ANY kind of RDA (in a Troll V2) on an 80W battery (iStick Power) that can handle down to 0.1 ohms as long as this RDA coil is at least 0.1 ohms? Meaning, as long as the resistance is compatible, it will vape or is there something more to it?


2. My 0.4 ohm coil in a specific tank (Smok Baby TVF4) is on my 80W battery. The coil is rated best at 50W to 80W. However, I can only increase the wattage to 40W before it starts having a burning taste. The recommended wattage is just too much for that coil. Why?


3. If I vape a 0.15 ohm coil at 75W and switch devices to another brand of coil (still 0.15 ohm) and another battery, would my ideal wattage still be 75W?

 

[Rossum]

Power divided by surface area of the coil = heat flux for that coil. That, plus other variables such as air flow and wicking have a big effect on how much power a coil can handle before it gets too dang hot and tastes burnt.

 

[HondaDavidson]

Because regulated and some protected mods don't use Ohms Law. They use Watts law.. to determine operational safety and function... as the battery safety is handled mistly by the PCB.. max ohm isn't as important max output is.



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[Angrygod50]

Because regulated and some protected mods don't use Ohms Law. They use Watts law.. to determine operational safety and function... as the battery safety is handled mistly by the PCB.. max ohm isn't as important max output is.



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Good for you ...It's about time someone noted that Watts law is not Ohms law. You could be my new hero.

 

[Carambrda]

1. If the mod can accept a .1 ohm coil build, that means the mod will be able to fire it so it will vape. (But this doesn't necessarily also mean it will be a pleasant vaping experience, nor does this necessarily also mean it will be safe.)

2. Maybe the people who put out those recommended wattages don't actually vape on the coil. Maybe the mod is outputting more power than the wattage you set it at (dunno if the iStick Power also does this, but there are many mods that do). Maybe @Rossum is correct and the airflow is too restricted for the way that you puff or the wick gets dry (not necessarily always a problem with the wick itself or with how you primed the wick... could also be due to how long you wait between puffs, thickness of the juice, how much force you use when you puff and the duration of the puff). Could also just be a broken mod or some certain problem with the atomizer or with how you set it up.

3. The ideal wattage is always the wattage that gives you the vape experience you like best. The 25mm Troll RDA 2 is the atomizer I started vaping on. With a dual coil fused clapton .3 ohms build in it at 80 - 90 watts the vape wasn't half bad, but still a far distance away from being excellent. It wasn't until four weeks later when I created my own dual coil staple staggered fused clapton .11 ohms build in it at 138 - 160 watts that it became pretty awe inspiring, in terms of both flavor and clouds. You can't usually expect to get a good vape from applying too many generalizations. Vaping is part science, the other part of it is art. Where science meets art, miracles happen.

 

[AndriaD]

You can't usually expect to get a good vape from applying too many generalizations. Vaping is part science, the other part of it is art. Where science meets art, miracles happen.

And don't forget the part about "user limitations" -- people laugh and scoff at my extremely-low-wattage vaping (<10w), but I simply can't handle much vapor with my asthmatic lungs, nor much heat either, so I've had to learn how to get something that tastes good and satisfies me, at the very conservative wattage levels and high resistance that I use. My Achilles RDA has a very tight draw, but for an asthmatic who wants a mouth-to-lung vape without a lot of air (because I simply don't have much air!), it's perfect.

Andria

 

[HondaDavidson]

And don't forget the part about "user limitations" -- people laugh and scoff at my extremely-low-wattage vaping (<10w), but I simply can't handle much vapor with my asthmatic lungs, nor much heat either, so I've had to learn how to get something that tastes good and satisfies me, at the very conservative wattage levels and high resistance that I use. My Achilles RDA has a very tight draw, but for an asthmatic who wants a mouth-to-lung vape without a lot of air (because I simply don't have much air!), it's perfect.

Andria

Not forgotten. ..... user limitations and desires are what determine how Art and science are applied.



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[AndriaD]

Not forgotten. ..... user limitations and desires are what determine how Art and science are applied.

True... but people need to be reminded that just because mods come with these outrageous wattage levels, doesn't mean you have to use those outrageous levels -- it's entirely possible to get a very satisfying vape at very low wattage, and high resistance -- though 2 ohms used to be considered low resistance! Now with all this subohm crap, 2 ohms is very high resistance!

It just depends on what the user can tolerate -- because a lot of "old smokers" have lungs so damaged, they really have to take it easy on vaping. Asthma, COPD, bronchitis.... very common in "old smokers"!

Andria

 

[KingPin!]

Power divided by surface area of the coil = heat flux for that coil. That, plus other variables such as air flow and wicking have a big effect on how much power a coil can handle before it gets too dang hot and tastes burnt.

This +1 ...coil length volume and mass, inner/outer diameter, heat flux, heat capacity, density, metal type and resistivity, wicking, airflow, all play a role in what you are observing OP

Plus you can mount coils to half or double resistence depending on the deck you go with (outside of single coil) requiring changes in wattage to fire up

I've been messing about reverse engineering steam engine calculator (only as I like to understand how things work) managed to do it for the most part the one thing they had to overcome was length... they have some hidden calculation which I haven't yet worked out seems silly but if you chose the bare minimum of everything the length they come out with is crap but it does give pretty much a spot on answer when it comes to resistence for the coil type... but length is integral to work out everything else they provide in wire wizard ...still working on it at the moment lol

 

[Carambrda]

True... but people need to be reminded that just because mods come with these outrageous wattage levels, doesn't mean you have to use those outrageous levels -- it's entirely possible to get a very satisfying vape at very low wattage, and high resistance -- though 2 ohms used to be considered low resistance! Now with all this subohm crap, 2 ohms is very high resistance!

It just depends on what the user can tolerate -- because a lot of "old smokers" have lungs so damaged, they really have to take it easy on vaping. Asthma, COPD, bronchitis.... very common in "old smokers"!

Andria

A satisfying vape is satisfying, always no matter how many times your mod or setup has been shat on by anyone who calls himself/herself "experienced", and the same applies to how you vape it. I know my RX300 can go up to 400 watts, but right now I'm using it to vape on a single big coil at 58 watts... still half a dozen times more watts than "at very low wattage" of course, albeit on paper especially next to those 400 watts it looks like small peanuts. I just like how it vapes, it's only my 2nd coil build but I'm the guy who built it and if some RUDE fuckass wants to disagree with me when I say my RX300 is not a shit mod the guy can sue me.

 

[Canadian Vaper]

There is quite literally no one calculation that can determine with outright certainty what wattage to run a build at.

Every Mod is different, just because two different mods are 75w doesn't mean they'll hit the same way, one can ramp up different than another.
Batteries as well are all different they'll release different amounts of energy.
Wicking is different every time you do it.
For low ohm, high wattage builds how much airflow the atomizer has plays an important roll and
your lung capacity/health, can you breathe in fast and hard without coughing just normally?

----------------------------------

Every build I use I always start out at low wattage and work my way up until I get The Flavor, The Warmth and Vapor Production I'm looking for although the flavor and warmth supersede vapor production and only go that high when I'm looking to make it cloudy....

 

[AndriaD]

A satisfying vape is satisfying, always no matter how many times your mod or setup has been shat on by anyone who calls himself/herself "experienced", and the same applies to how you vape it. I know my RX300 can go up to 400 watts, but right now I'm using it to vape on a single big coil at 58 watts... still half a dozen times more watts than "at very low wattage" of course, albeit on paper especially next to those 400 watts it looks like small peanuts. I just like how it vapes, it's only my 2nd coil build but I'm the guy who built it and if some RUDE fuckass wants to disagree with me when I say my RX300 is not a shit mod the guy can sue me.

Yes! I consider myself fortunate that when I started, 15w was the max possible, unless you sub-ohmed with a mech, and then shortly, 20w became possible with the Sigelei Legend -- though it was really pricey! But at those low wattages and high resistance levels, I was able to learn to vape, and learn to build and mix my DIY to suit my very-tetchy lungs. If I had to start now, with all these multi-hundred watt mods, and hardly any attys that offer tight draw, I probably wouldn't be able to vape at all.

Andria

 

[Rossum]

If I had to start now, with all these multi-hundred watt mods, and hardly any attys that offer tight draw, I probably wouldn't be able to vape at all.

I wonder if this is one of the reasons that we seem to have fewer new vapers. Most of the gear available now isn't really suitable for someone just trying to switch from smoking cigs. Sorry, but I've never seen anyone DL their cigarettes. And even if someone finds equipment appropriate to switch with, the juice available in a lot of places these days isn't gonna cut for most people in the kind of gear that best simulates smoking. 3mg? 6mg? Cut me a break. I'm almost 3-1/2 years in and I'm not quite down to 12 yet.

 

[AndriaD]

I wonder if this is one of the reasons that we seem to have fewer new vapers. Most of the gear available now isn't really suitable for someone just trying to switch from smoking cigs. Sorry, but I've never seen anyone DL their cigarettes. And even if someone finds equipment appropriate to switch with, the juice available in a lot of places these days isn't gonna cut for most people in the kind of gear that best simulates smoking. 3mg? 6mg? Cut me a break. I'm almost 3-1/2 years in and I'm not quite down to 12 yet.

I'm quite sure that's true, and also why the few newbies who do show up, are constantly complaining about coughing, scratchy throat, etc -- it would be VERY hard to get started as a vaper, with the huge clouds all these sub-ohm things put out; smokers' lungs are almost always quite irritable and it can take quite some time for them to calm down after the coffin nails are gone -- and for folks like me with asthma (or COPD, bronchitis, etc), they may never calm down.

I'm about to assist my son into transitioning from smoking to vaping, and I'm just really glad that I've still got a decent quantity of XL standard-resistance cartos under the counter, and those old vv3s that still work just fine -- he's not [yet] interested in a huge box mod, and sure as hell isn't interested in the gross clouds he's seen from other vapers out "in the wild". I'll be working him towards switching over to rebuildable attys, certainly, simply for the cost savings plus great taste and insulation from the vagaries of the fucking FDA... but I ain't giving up my Achilles! He can have the old Kayfuns!

Andria

 

[The Cromwell]

Power divided by surface area of the coil = heat flux for that coil. That, plus other variables such as air flow and wicking have a big effect on how much power a coil can handle before it gets too dang hot and tastes burnt.

THIS!

It is a complex thing and there is no one easy answer.
Ohms law is correct and nothing missing from it.
Several other aspects of physics come into play though as well.

 

[Swerved]

The majority of the time people stress the importance of understanding Ohm's law so you won't blow your face off from trying to draw 50A of a 20A battery... But as far as the vape/flavor etc goes, look at like this (and it's been explained adequately in the above posts as well):

A 1-ohm coil made from 28g (Kanthal) wrapped around a 2mm mandrel 6 times, has about 56.3 mm2 of surface area.
A 1-ohm coil made from 26g (Kanthal) wrapped around a 2mm mandrel 9 times, has about 113 mm2 of surface area.

Both coils are 1 ohm, but at 30w the 1st coil will be burning hot because the lesser amount of surface area (and volume of metal) doesn't require that much wattage to heat up. The second coil will be much better at that wattage because the increased surface area and volume of metal can take the heat for longer without burning..

Like other posters have stated, it's more about wattage and heat flux when it comes to not burning the cotton than it is about Ohm's law even though Ohm's law is in play.

 

[Canadian Vaper]

The majority of the time people stress the importance of understanding Ohm's law so you won't blow your face off from trying to draw 50A of a 20A battery... But as far as the vape/flavor etc goes, look at like this (and it's been explained adequately in the above posts as well):

A 1-ohm coil made from 28g (Kanthal) wrapped around a 2mm mandrel 6 times, has about 56.3 mm2 of surface area.
A 1-ohm coil made from 26g (Kanthal) wrapped around a 2mm mandrel 9 times, has about 113 mm2 of surface area.

Both coils are 1 ohm, but at 30w the 1st coil will be burning hot because the lesser amount of surface area (and volume of metal) doesn't require that much wattage to heat up. The second coil will be much better at that wattage because the increased surface area and volume of metal can take the heat for longer without burning..

Like other posters have stated, it's more about wattage and heat flux when it comes to not burning the cotton than it is about Ohm's law even though Ohm's law is in play.

Yeap, like I said there's just too many variables for a AIO equation.

Best thing to do is start your wattage low and slowly increase it until you hit that sweet spot, if you can't find that sweet spot maybe try a different coil...

I love to vape between 0.2 and 0.3 ohms but currently I'm running a 0.6 at 30w just in it's sweet spot and I love it...