Dual Coils explained (from the discountvapers website)
"A dual coil carto consists of two coils of the same resistance. They are wired in parallel so the total resistance is half the resistance of either coil.
For example:
The total resistance of the 1.5ohm dual coil is 1.5ohms, but the resistance of either coil it contains is 3ohms. Both coils are actually 3.0ohms individually, together they are not 6.0, they are 1.5ohms
A 1.5ohm carto at 3.7V would be drawing 3.7/1.5=2.47 amps. But the single coil is burning at 3.7^2 / 1.5 = 9.13 Watts, while each coil of a dual coil 1.5ohm carto is burning at (3.7^2/1.5) / 2 = 4.57 watts. You are spliting the power between the two coils."
Note: I don't use dual coils, so I haven't studied the formulae and won't pretend to understand it. I copied it from discountvapers.com for my definitions file.