The question is, at what voltage are you pushing the 3 ohms. I like a nice warm vape so that's why I said I keep it at about 8 watts. My juice's sweet spot is right around that range. Any hotter and it burns and any cooler I don't get the warmth I like. I use a DiD (D20) with a 2ohm coil set-up and run it a about 4 volts.
Yes, you can get the same warm vape out of a 3ohm coil but you have to crank up your volts to about 5 volts which is still going to drain your bats at the same rate. Kinda like 6 of one vs. half a dozen of the other.
Nope, definitely not draining at the same rate... It took me a while to understand why, as my thinking was the same as yours: "hell, 7W are 7W anyway"... Guess what, I was wrong.
Let's take your example, 8W; you can achieve 8W for instance by either using (just to take two extremes):
1.5ohm at almost 3.5V, drawing
2.3A in the process, or 3ohm at 4.9V, drawing
1.6A.
if we suppose the battery capacity to be 2000 mAh, the above A rates would deplete it in 2000/2300=
0.87h (52m) with 1.5ohm resistance, but in 1600/2000=
1.25h (1h15m) @3ohm. That means you get 30% more vape time!
Of course that's theoretical, in reality the PWM (step-up) circuit will suck some more battery on its own at 4.9V than at 3.5V, but you get the idea... My observation is that now my batteries last 20-25% longer than before, perhaps even more, and I've only changed the atom resistance.
Give it a try (and buy me a virtual beer if it works for you as well). Heck, what have you got to lose?
PS: still empirical, based on
my testing, but I suspect the PWM of the provari to become more power hungry beyond 5V, give or take.