Start simple and work your way up. Yes, this applies to coils but also, you know, life.
I agree with this. I call it the K.I.S.S. Principle. (Keep It Simple, Stupid)
In my personal experience, when building coils for a mech the less mass the better: Less ramp up time and less drain on the battery. I consider the factor of surface area to be over-stated when comparing it against ramp up time and drain on the battery on a mech. YMMV. I've vaped on many exotic coils (used to work in a vape shop) and never experienced any benefits over using simple compressed coils on a mech.
I use 26 gauge Kanthal. Two 1.2 ohm simple compressed coils (0.6 ohm combined) gives me a great vape on a mech, gives me some margin of safety over and above the continuous discharge rate (Samsung30Q 20A 3000 mAh), and is less draining on the battery.
1.0 ohm = 4.2 amp draw
0.9 ohm = 4.6 amp draw
0.8 ohm = 5.2 amp draw
0.7 ohms = 6 amp draw
0.6 ohms = 7 amp draw
0.5 ohms = 8.4 amp draw
0.4 ohms = 10.5 amp draw
0.3 ohms = 14.0 amp draw
0.2 ohms = 21.0 amp draw
0.1 ohms = 42.0 amp draw
0.0 ohms = dead short = battery goes into thermal runaway
Everyone is free to set their own safety parameters, and I can only say what mine are.
I try to never exceed 50% of the CDR (continuous discharge rating) of a fully charged battery (4.2v). So with a 20A batteries, that would be 10A. The above
Ohm's Law Calculator tells me that a .4 ohm build is as low as I would want to use.
The reason that I place a 50% limit is because as a battery ages the mAh of the battery degrades, as the mAh degrades so does the batteries c rating (amp limit). So down the road, your 20A battery may only be a 10A battery.
