Here's an answer I wrote up in another thread....Hope this helps...
You asked.....Here's how wattage, resistance, voltage all mix together.
Before we start, Watts at the coil is what produces the flavor, higher wattage -> Higher Temperature -> more flavor and more vapor (until you go too high and burn the juice....)
Ohms Law and Watts Law state the following for a simple DC circuit. Watts = Voltage*Current.... Current = Voltage/Resistance. So Watts = Voltage*Voltage/Resistance
When you had an Ego Stick Battery or unregulated battery, The voltage output of your battery was fixed. Thus the only way to coax out more temperature at the coil was to lower it's resistance. This is why people use 1.8 ohm coils or lower on standard non regulated batteries. If Voltage remains constant, then when resistance goes down, Watts goes up...More flavor, More Temp.... Problem is. It's not easy to set the resistance to a coil. Once it's "wrapped" it's pretty much set. So you are stuck with buying a lower resistance coil from the manufacturer, or coiling your own heads.
So The Variable Voltage Battery came into play. I can't easily change resistance, but I can raise voltage. Thus if resistance stays constant, when I increase voltage, I increase wattage. Much easier for us to control the flavor. Most people simply set their batteries at a low value and then bump up the voltage until it "tastes right". If you already know what your coil resistance is, and what Wattage you want at the coil, then you can calculate what voltage you need to get to your target wattage. There are also Voltage and resistance tables online that allow you to have a good starting point for your adjustments.
One little problem with variable voltage. Let's say I take off one tank and put on a new one....Even though Kanger, Innokin, or whoever says that it's a 1.8 ohm coil, it can actually be up to .3 to .4 ohms different. So when I put on my new tank with it's atty and take a draw at my desired voltage, all of the sudden, the vape is not as intense, or tastes burnt. This is because resistance varies from coil to coil. It can also vary over the life of the coil. So with variable voltage, you have to continue to tweak your settings when you change atty heads or as the atty head ages.
Here's where Variable Wattage comes in. Let's say I discover that I like vaping a particular juice at 7.5 watts. I may have discovered this using variable voltage....(4.3 volts, 2.5 ohm resistance). So now I set my Variable Wattage to 7.5 watts. The device will measure the coil resistance and then automatically adjust the volts up or down to produce 7.5 watts. If I put my juice in a new tank, and the atty head changes resistance, I still get 7.5 watts and the same flavor....If my coil changes in resistance over time...I still produce 7.5 watts and my flavor stays consistent.
So that's how resistance plays into the whole variable voltage/variable wattage discussion and why lower resistance heads are preferred on standard non regulated batteries.
One final word. If you have a battery that does variable voltage and variable wattage, realize these are TWO DISTINCT and MUTUALLY EXCLUSIVE modes. If the battery is in variable voltage mode, it will fire at the set voltage regardless of the resistance of the coil. If the battery is in variable wattage mode, it will automatically adjust the voltage of the battery to maintain the set wattage.
