Building Wicks: Electricity, volts, ohms and watts. How it all fits together.

[DutchFlyer]

Ok, I'm new to vaping, but not so new to electrics.

Here's what I know, and how I think it fits together. If you see anything that seems incorrect or inconsistent, by all means call me out!

I'm writing this because in all the threads I've read, there's one thing missing: How power (wattage) is APPLIED to the e-liquid.

First, the equations. Thank you Mr. Watt and Mr. Ohm.

"Ohm's Law" -
V = I x R
aka, Voltage = Current x Resistance
aka, Volts = Amps x Ohms

"Watt's Law" -
P = V x I
aka, Power = Voltage x Amperage
aka, Watts = Volts x Amps

Combine the two laws, and the result is:
P = V x ( V / R )
aka P = V^2 / R
aka Power = Voltage-squared divided by Resistance
aka Watts = Volts-squared divided by Ohms

All very nice and neat.

Now apply it to a wick:

If you use a short piece of fat wire, the resistance will be very low. There's very little length for the voltage to have to push its way through, and the "pipe" is plenty wide.

If you use a longer wire, or a thinner one, there's more length to push through, and a narrower cross-section to push through. Thus more resistance. And if the resistance goes up, the power (wattage) goes down (for a constant voltage).

Less power means less vapor. So why on earth would we want anything other than short little fat wires? That would offer the lowest resistance, right? And thus the highest power, right?

Well, sure, but it's only applied to a very small amount of e-liquid. So unless your wick is, well, "wicking" very very well, you're going to dry up and be heating, well... nothing, with all that power.

So, it's a trade-off. We want to heat a lot of liquid to get a lot of vapor. We also want to heat it quickly, and to a sufficient temperature.

So what's the answer? Make a longer, fatter wire that contacts more e-liquid. Longer means higher resistance, fatter means lower. Compensate for any higher resistance by stepping up the voltage, and thus the power.

Now, how does a double-wick fit in? Well, the two resistance wires are usually wired in parallel. This actually equates to the same behavior as one thicker wire, and thus less resistance. So, with the same voltage, you're putting more power to the e-liquid.

So, now that we have a plan for low ohms and high watts... we have to worry about amps. Basically, if we do too good a job at creating high power, we can overdraw the battery. Just be careful. if you're going to go the high power route, stick with high quality, high draw batteries, and use some sort of thermal protection, be it an IMR battery, a mod with protection built in, or something like a short-stop.

Clear as mud?

 

[williebb123]

your getting there now build 3-4 different coils and see which one you love the most and the try a few micro coils enjoy and have fun

 

[MattyB1503]

Looks like you've got it and you're asking all the right questions. That's is the kicker though; wattage only describes how much power you'er pushing at the coil(s). In no way does it specify coil temperature. There's also airflow through the atty, top cap or expansion chamber size, wick saturation/ how well material wicks, how wicking material effects flavor, coil ramp up time, ease of build, ect. ect. to consider. To top it all off certain e-liquids taste better at different temperatures; then, finally, taste is subjective... You might try a build that people are raving about but think it's not for you.

So as williebb says, time to tinker..

 

[twgbonehead]

The whole point of an atomizer is to bring a quantity of e-liquid up to the correct temperature for it to vaporize and be heated, in order to provide the user with a pleasant vaping experience. The device also needs to run using voltages available from common batteries.

You assume that getting the right amount of power into the coil is the only thing that matters, and that is where you are in error. The concentration of the power dissipation is absolutely the critical element. Focus all the power in a small area (i.e. one coil turn) means that the vapor will be hot, burned, and thin. Distribute the power over a wide area and you get no vapor at all, just a bunch of warm e-juice. The magic is designing a coil (and environment, like wicks) that is right in the middle; gets lots of juice to the right temperature with the least amount of power.
Ohm's law doesn't cover that aspect of the problem, it is only concerned with how much power is dissipated in total, not with where the power is distributed. It doesn't deal with temperature or thermal issues at all, and the whole point of the exercise here is to generate the best heat profile with the least power using battery voltages that are available.

 

[War Mouse]

A good coil and wick build goes so far beyond applied electronics. You could probably cover about half of a physics 101 course using wick and coil builds for your labs. Thermal conductivity, fluid dynamics, molecular cohesion, pressure systems. But really, as long as you can check the actual resistance of the coil the rest of it can be ignored. If you can find the Ohms, you can build amazing coils and get great vapes through trial and error. I understand the entirety of the technical side, but I still brute force my coils until I get a good "taste". That's what I tell people to do. Find a resistance that works on your device well and just fiddle with the thing until it gives a good vape.