Why wattage, what we care about is current!

[Hans Wermhat]

High and low resistance are relative terms really. If you use 28G kanthal, 8 wraps @ 2mm single coil is around 1.4 ohms. A reg mod will put 6.2 volts to it at 27.5W. A dually build with 24G N80 at 3mm is .3ish ohms, and your reg mod will put 3.4V to it at the same wattage. Even though the KA1 build is smaller and higher ohm, it will still draw more power out of your batteries. There are too many variables in vaping to make a blanket statement like that.

 

[tj99959]

Can anyone else confirm this? This seems to be counterintuitive, but my electrical physics is lousy, as evidenced by this thread.

2 ohm @ 4v = 2a
3 ohm @ 4v = 1.33a

works out fine unless you want to run it through a regulating ckt. Then all bets are off.

 

[VictorViper]

Can anyone else confirm this? This seems to be counterintuitive, but my electrical physics is lousy, as evidenced by this thread.

Confirming. I can't do any better than the faucet analogy, though.

 

[UncleChuck]

Current tells you almost nothing about the type of performance you will get from a coil, it's just not a useful figure. You can make two builds that perform similar at different amperage, and you can have builds that perform wildly different at the same amperage.

Consider the following builds:

1.5 Ohm set to 50W, current will be less than 6 amps through the coil. Still 50W of power.

0.2 ohm set to 50W, current will be almost 16 amps, more than double the current, still just 50W of power.

Now because of the difference in coil size and/or wire diameter between the two builds it's impossible to do a direct comparison, but the .2 build will not put out double the vape of the 1.5 ohm build just because it's got a lot of current running through it. The two builds are running the same amount of power, and IF their coil's mass and surface area were identical they would be putting out the same vape. In other words, the difference in vape between those two builds comes from the difference in the physical (not electrical) qualities of the coil.

As others have mentioned we have access to much better stats than watts or volts with build calculators like Steam Engine out there, but even with all the limitations involved with using watts to describe a vape, it's still more accurate than using amps.

 

[VictorViper]

...it's just not a useful figure.

Awesome post, but I wanted to add that it is of critical importance when determining safe operation with respect to your cells. Probably redundant to say and I know it wasn't remotely the point, but I figure better to mention it than leave it unsaid.

 

[Cullin Kin]

Now I see what it is about. But what you are talking about is not a heat flux, but - very approximately - a heat flux density, or heat rate per unit area. And "heat rate per unit area" describes things in much more understandable way than incorrectly used "heat flux".
What's more, we all know we cannot use just watts, "heat flux" or other single parameter to compare different builds.

You are totally right. The way we use the term heat flux is not correct since it truly involves two quantities, time and area, not just area. I think Steam Engine just didn't have enough room for 'heat rate per unit area' in their little diagnostics box at the end. lol

But then we get in to the question, what is heat? Yehaw, thermodynamics.

 

[bwh79]

Can anyone else confirm this? This seems to be counterintuitive, but my electrical physics is lousy, as evidenced by this thread.

Amp drain is equal to voltage divided by resistance. So as the resistance goes up, the amps go down. Think of it like a sprinter, running underwater. The water is thicker than air, and slows the runner down (it "resists" his movement) compared to running on dry land, where the atmosphere provides very little resistance. If the pool were filled with molasses instead of water, the resistance would be higher still, and the runner would move even more slowly.

 

[Boden]

What if we used Joules per second?



*runs away again*

 

[Boden]

stupid double post

 

[crxess]

Can anyone else confirm this? This seems to be counterintuitive, but my electrical physics is lousy, as evidenced by this thread.

I have to... sort of........agree with you.

Higher resistances generally allow for builds with thinner wire(less load) and faster heating while not dramatically changing the resistance level.
i.e. some Vape 28ga. at 1.4ohms while others buy 1.8ohm 32ga. coil heads.

You can see by the wire alone the required power to heat would drastically reduce function of a 510 or even 350mah Ego battery. The current required to reach vapeable temps alone on a heavier wire would quickly deplete them.

Obviously there is more to perfecting a vape than simple numerical choice.
Will one stay within the 3.7v Box or expand to 12v.
Do you have room for a 24 coil wrap or only 10 coils?
Is your Air Flow capable of keeping up with your power choices?

Remember - If Laws were not meant to be broken we would never have gone into space...... or invented regulated mods.(well, at least twisted)

 

[Alien Traveler]

Can anyone else confirm this? This seems to be counterintuitive, but my electrical physics is lousy, as evidenced by this thread.

Watts determine battery drain. With higher resistance you can vape at lower watts.

 

[crxess]

But then we get in to the question, what is heat? Yehaw, thermodynamics.

Technically?
Anything above absolute -0-

I prefer mine around 78 degrees and 20 percent humidity

 

[Cullin Kin]

Technically?
Anything above absolute -0-

I prefer mine around 78 degrees and 20 percent humidity

You're thinking of temperature. Heat and temperature are related, but are completely different concepts.

 

[bwh79]

Technically?
Anything above absolute -0-

I prefer mine around 78 degrees and 20 percent humidity

That's temperature. Heat and temperature are not the same thing. Temperature is an objective comparative measure of hot or cold; heat is not a state or property of a single system or body, but rather the transfer of energy (other than by transfer of matter) from one body to another.

 

[GoBlue88]

Watts determine battery drain. With higher resistance you can vape at lower watts.

Say you vape at the same wattage and higher resistance. That's same battery usage no? A regulated mod would just adjust voltage, correct? But that would have no impact on battery life.

 

[GoBlue88]

Current tells you almost nothing about the type of performance you will get from a coil, it's just not a useful figure. You can make two builds that perform similar at different amperage, and you can have builds that perform wildly different at the same amperage.

Consider the following builds:

1.5 Ohm set to 50W, current will be less than 6 amps through the coil. Still 50W of power.

0.2 ohm set to 50W, current will be almost 16 amps, more than double the current, still just 50W of power.

Now because of the difference in coil size and/or wire diameter between the two builds it's impossible to do a direct comparison, but the .2 build will not put out double the vape of the 1.5 ohm build just because it's got a lot of current running through it. The two builds are running the same amount of power, and IF their coil's mass and surface area were identical they would be putting out the same vape. In other words, the difference in vape between those two builds comes from the difference in the physical (not electrical) qualities of the coil.

As others have mentioned we have access to much better stats than watts or volts with build calculators like Steam Engine out there, but even with all the limitations involved with using watts to describe a vape, it's still more accurate than using amps.

This really helps clarify. Assuming a magical mod with no limitations on resistance it can fire at, wattage etc. Does this not suggest that know should determine the physical characteristics of their coil build we prefer, then just select the wattage we know we like?

 

[Fit_Four_Life]

Say you vape at the same wattage and higher resistance. That's same battery usage no? A regulated mod would just adjust voltage, correct? But that would have no impact on battery life.

This is exactly what I want to know.

With which coil will my battery last longer when my VW mod is set at 12.5 watts? A 0.5 ohm coil or a 1.2 ohm coil? Or does it make no difference in battery life?

 

[Boden]

Say you vape at the same wattage and higher resistance. That's same battery usage no? A regulated mod would just adjust voltage, correct? But that would have no impact on battery life.

Resistance wire is almost 100% efiecient at turning electricity into heat. But thicker wire has more mass and heats up slower and cools down slower. To get the same ramp up time as smaller wire you have use more power. Smaller wire also has less surface area away from the wick. So the smaller wire is more efiecient at transferring heat to the liquid.

If you were only heating the wire into free space 25W radiated heat per second uses the same amount of energy for thick wire as it is for small wire.

 

[bwh79]

Say you vape at the same wattage and higher resistance. That's same battery usage no? A regulated mod would just adjust voltage, correct? But that would have no impact on battery life.

This is exactly what I want to know.

With which coil will my battery last longer when my VW mod is set at 12.5 watts? A 0.5 ohm coil or a 1.2 ohm coil? Or does it make no difference in battery life?

It will have no impact on battery life. Keep in mind that whatever voltage the mod is delivering to the atomizer, the battery only ever outputs a voltage equal to its current charge (that's current as in "right now," not current as in "I = V/R"). As they say, "power in = power out" so if the device is delivering 12.5w to the atomizer, that means that it must necessarily be drawing 12.5w (give or take a few % for powering the device itself, and energy lost due to less than 100% perfect efficiency) from the battery, as well. Since the battery outputs a constant voltage at, let's say it's charged to it 3.7 volts, then to deliver that 12.5 watts requires drawing a current of 12.5 / 3.7 = roughly 3.3 amps from the battery. Note that nowhere in this calculation does the atomizer resistance play a part. That 12.5w will draw 3.3 amps from the battery, regardless of whether it's pumping those watts into one ohm, or ten.

 

[Alien Traveler]

I apologize for my dumb post (deleted)
Some Friday nights could be really challenging on my mental abilities.