Here's (mostly) everything you need to know about mech mod safety and the electrical side of it:
given:
Nominal Voltage : 3.7V
Capacity : 2000mAH
Lowest Discharge Voltage : 2.50V
Standard Charge : CC/CV ( max. charging rate 2A )
Cycle Life : > 500 cycles
Max. continuous discharge rate : 10A
Operating Discharge Temperature : -10 - 60 Degree Celsius
And:
Power (in watts) = Volts x Amps = Volts squared / Resistance (ohms) = Current (amps) squared x Resistance (ohms)
So if we know basic algebra (or we google an "ohm's law calculator," we can determine the follwoing:
in order to maximize the amperage draw without exceeding the battery limitation listed above (call it 8 amps to be safe):
power (in watts) = volts x amps
power (in watts) = 3.7 x8.0
power (in watts) = 29.6 watts
29.6 watts is the max you can (safely) draw from your setup, so now we want to build a coil that will draw 29.6 watts.
from above:
power (in watts) = volts squared / resistance
29.6 = 3.7x3.7 / resistance
29.6 = 13.69 / resistance (multiply both sides by "resistance")
29.6 x resistance = 13.69 (divide both sides by 29.6)
resistance = .4625
so, your coil has to be .4625 ohms in order to pull 30 watts and maximize your batteries at 8 amps.
This chart is for A1 type of Kanthal wire per inch, other grades are different.
28 awg (Ω/in) 0.5 ohms
30 awg (Ω/in) 0.7 ohms
31 awg (Ω/in) 0.9 ohms
32 awg (Ω/in) 1.2 ohms
33 awg (Ω/in) 1.4 ohms
34 awg (Ω/in) 1.8 ohms
35 awg (Ω/in) 2.3 ohms
36 awg (Ω/in) 2.9 ohms
The lower the ohms per inch, the more wraps you will need (to get our .47 ohms), this can be a trade off as the thinner wire needs less wraps but also has less surface contact to the liquid. remember that the ohms-per-inch resistance table takes into account the entire length of the coil, including the tails.
so for 28 awg kanthal, we need just under an inch of wire to get .47 ohms. so what you can do is measure from the end of the wire one inch, and mark it with a permanent marker. that way, when you are winding your coil, you can see that the black mark needs to be where you cut it, and you can wrap your coil accordingly.
problem is that an inch won't cut it, and we need closer to 2 inches. so we're not going to be maxxing out our batteries if we're using 28 ga wire and wrapping more than one wrap
in summary: the reason why ppl want to use a larger gauge of wire, is because a larger gauge of wire has less resistance, and that means you can have more turns on your coil (and more surface area) than if you use a smaller gauge of wire. this also requires more power. the only thing you have to keep in mind, is that your power source (battery and mech mod) has to be able to put out the amount of power (in this case, about 8 amps). mech mods do not have any electronic components, so you don't have to worry about blowing up a nice electrical mod.
if you have an electric mod that can only support 5 amps, but is also limited to 1.3 ohms (like the vamo, provari or svd), you can then do the math and figure out that you can only put out 2.8 amps at 1.3 ohms, and 10.5 watts. so in order to maximize our 1.3 ohms, we could use 2.6 inches of 28ga (which would be a very long coil with many turns), 1.85 inches of 30ga, 1.4 inches of 32 ga. the only limitation at that point is how much space you have to wind the coil in. if you're winding a genesis, you might be able to wind a 2.6 in coil if you made the windings really close together. but if you're winding a coil for a protank or similar, the rules change. you have a lot less space to work in, so you have to pick a wire size that will allow you to wrap a coil with the right resistance in the physical space in the coil head. for protank coils, i personally use 32 ga kanthal in a 4/5 wrap, that gives me 2 ohms, and i use 2 pieces of 3mm silica (wrap both pieces, no flavor wick here).
hope i didn't confuse the crap out of you
