The TRUTH about sub-ohm vaping on mech mods

For a long time I've been vaping on mech mods + drippers with single-coil setups at 0.5 - 0.6 ohm resistance. So the power was about 25W and everything was cool. Then I wanted to try some stronger configurations. The easiest way seemed just to add second 0.6 ohm coil and get twice lower resistance and hence to double the power. I did it but did my general vaping impression also  doubled? ABSOLUTELY NO! So I started to wonder why? Below I try to explain this phenomenon.

Let's start from the experiment:
* I take the Sony VTC4 battery fully charged to 4.2V,
* and the RDA with "easy" 1.1 ohm coil:

 

* then I connect the mech mod and measure the voltage on atty's posts by use of multimeter:

Hmmm, there is not so good: we get almost 0.7V voltage drop, and it means that instead of expected 16W we get only about 11W. Only 70% of expected power.

And what will happen if  I connect coil with approximately twice lower resistance?

Will I double the power? Let's check the voltage:

Now we have 0.9V voltage drop, so we get only 18.7W of power INSTEAD of expected ~31W. Only 60% of expected power.


WHY?

Generally due to the parasitic resistances of our circuit. In slight simplification it would look like this:

So we have:
* battery with internal resistance 0.03 ohm (optimistic assumption) and 4V (for calculation simplicity),
* the rest of the circuit "on the way" to the coil: threads, contacts, screws on posts, etc. - and also optimistically assume that everything has 0.05 ohm,
* an example coil with 1.5 ohm resistance.

And through it all the CURRENT flows. And it causes voltage drops wherever it can. So:

Not bad - only 10% difference from theory - nice.
And what if we do the coil with 3 times less resistance? Will the power increase 3 times?

As you can see NO - we get only 70% of expected (theoretical) power! 

Almost 30% of the generated power is wasted on heating elements other than the coil!

And then it gets worse - just look at the graph of power (calculated according to the above scheme) for decreasing the resistance:

As you can see at 0.2 ohm half of power goes into air !!

And WHAT ABOUT VV/VW MODs??

I repeated the test using vv mod based on GE Naos Raptor chip, at 4.23V:

And what the real voltage on posts was? 

As you can see is MUCH BETTER: 

* for 1.11 ohm we get ~95% of expected power (on mech mod we got ~70%) 

* for 0.57 ohm we get ~88% of expected power (on mech mod we got ~60%)