VV vs VW
There is a lively debate going on discussing which is better: variable voltage or variable wattage ...
So, which is better? Variable Voltage? or Variable Wattage?
The answer is not as clear cut as it seems. Let's look at variable wattage first, since that appears to be the consensus.
Variable wattage is a feature available on many advanced personal vaporizers, and some mid-size personal vaporizers. It lets you dial in a wattage, and the electronics of the device then determine the resistance of the coil, and adjust the power going to the coil so that you end up with the wattage you dialed in.
Most vapers prefer a wattage around 8.5. One manufacturer even has a product that capitalizes on this: the Innokin Cool Fire 1. It is factory set to 8.5 watts. When you click the fire button, the Cool Fire 1 determines the coil resistance (ohms) and adjusts its power to deliver 8.5 watts. It doesn't matter which clearomizer you are using or what the resistance of the coil is in that clearomizer – you get 8.5 watts. From the first puff through to the last on that coil, you will get a consistant vape. The coil could be dirty and wearing out, but until it is totally dead, you get 8.5 watts. Even if you change clearomizers with a different coil resistance, you still get 8.5 watts. The vaping experience should be identical while you use the Cool Fire 1. This is consistency and convenience, totally.
That's the advantage of variable wattage, convenience and consistency. There is no need for you to work out any formulas based on Ohm's Law. No need to fiddle with any settings, just click the fire button and vape.
Variable voltage is just that, it varies the voltage the battery is delivering to the coil so that you can achieve a more "dialed in" vape. Let me give you an example: if you are using a clearomizer with a 2.4 ohm coil and you prefer vaping around 8.5 watts, you would need to set your voltage to 4.52 volts to achieve that. That's what Ohm's Law calculates. Volts is equal to the square root of Watts times the Resistance. The formula looks like this:
V =SQRT(P x R)
V = SQRT(8.5 x 2.4)
V = SQRT(20.4)
V = 4.516636
V = 4.52 (note: rounded out)
V = Volts
P = Power (watts)
R = Resistance (ohms)
I = Current (amps)
SQRT = square root of
A quick note: the Excel spreadsheet formula for this would look like: =SQRT(8.5*2.4). And, also note that we have an Ohm's Law calculator on this site that you can use anytime.
Sitting down to figure this all out usually means a pad and paper or a calculator handy. That's why variable wattage is so convenient, the advanced personal vaporizer does it all for you.
However, what if you have a twist or spinner style eGo battery, or an advanced personal vaporizer with only variable volts? Does that mean you are at a disadvantage? Absolutely not ... there are advantages to having variable volts. Let's look at those advantages!
The preference for variable wattage at 8.5 may be common, but it does have some draw backs. What if you have an eLiquid that needs an extra "kick" to get throat hit? What if you have an eLiquid that is a bit on the thick side? What if you have an eLiquid that is a bit low on flavor? Well, you would want to kick your wattage up over 8.5. What if you had a personal preference to vape at 10 or 11 watts? What if you wanted to match the cloud chasers and vape at 30 watts? 35 watts? 40 watts? Yes, it is possible to get huge clouds of vapor with your eGo or advanced personal vaporizer. If your system can adjust voltage up to 6 watts, even better ... then you can get to 50 watts, maybe even 60 watts through the coil.
Here's how it works. Ohm's Law states that you have two fixed or known quantities. With variable voltage, you have the coil resistance (ohms) and you can set the voltage to whatever you want. What you can't set is the wattage. To do that, you vary your voltage based on the coil resistance. Let's say that you want to vape at 11 watts and you have the same 2.4 ohm coil. The calculation would look like:
P = 11
R = 2.4
V = SQRT(11 x 2.4)
V = SQRT(26.4)
V = 5.138093
V = 5.14 (note: rounded out)
... so, you set your Volts to 5.14 and you are vaping at 11 watts.
Now lets look at vaping at 30 watts. Recall that Ohm's Law states that you have two known quantities. So, let's determine what coil resistance we need to vape at 30 watts:
P = 30
V = 6
R = V(squared) divided by Power
R = 6(squared) divided by 30
R = 36 divided by 30
R = 1.2
So, you would need to change to a 1.2 ohm coil to get 30 watts with the highest possible setting of 6 volts from your advanced personal vaporizer. (By the way, most eGo batteries are limited to 4.8 volts maximum output, that would limit you to 15.36 watts when using a 1.5 ohm coil – that's the lowest resistance coil I know of that is commercially available). If you are able to output 6.0 volts, with the lowest resistance commercially available coil of 1.5 ohms you would get 24 watts.
If you want more than 24 watts, you need to get into Do-It-Yourself rebuildable atomizers, or RBAs. It is easy enough to master, but you are getting further and further away from "convenience". The cost factor is not an issue: with DIY your costs can be a bit lower than buying pre-made coils. Note that I said "can be a bit lower" ... you can get carried away with some expensive stuff here. I've gone to vapemeets and seminars where experts go through tutorials on how to build your own coils. It doesn't take long, it can be quite satisfying knowing that you are vaping the very unit you built. But it can also be frustrating and can be time consuming.
Best of luck evaluating all the different options.
PS. By the way, to get 50 watts at 6 volts, you would need a coil that is 0.72 ohms. To get 40 watts at 6 volts, you need a 0.9 ohm coil. And, to get 35 watts at 6 volts you need a 1.03 ohm coil. At the seminar I attended, there was one instructor that could build 0.25 ohm coils (that is, based on two 0.5 coils in a dual setup).