Ok so I notice that with higher ohms 30 watts pulls less amps on a 1.3 coil than on a 9 or below- my question for you fine folks is this: Which will last longer in a well regulated mod- 30 watts with a higher ohm, or something .9 or lower?
I assume you're talking strictly about regulated mods here. So I'm not sure whether you're talking about the current at the coil or the current at the battery here.
But here's the thing. In theory it's quite simple if you feed 30W to a coil, with a regulated mod, regardless of the resistance of the coil, the current going through the battery is exactly the same and depends solely on the battery's voltage.
So, say the battery's voltage is 4V when you fire the mod, the current will be 30/4 = 7.5A. The mod takes care of stepping up or down the voltage depending on the coil's resistance.
In practice however, it's not that simple:
1/ The mod's circuitry is not 100% efficient in converting the voltage, and the inefficiency may be more or less important at certain coil voltages.
2/ If your mod is a bit cheesy, the wire that connect the chip to the pin may be too thin (quite common in China-made mods). As a result, if you install very low resistance coils, the wire's resistance starts to become non-negligible compared to that of the coil. As a result, some power is lost in the wire, and you have to increase it to get the same vape as with a higher resistance coil, which of course increases the current through the battery.
3/ Not all mods convert the voltage linearly. Many mods use power width modulation (PWM). What that means is, the average current drawn from the battery may be constant, but the instantaneous current may be quite a lot higher. In these mods, the lower the coil's resistance, the shorter the PWM's duty cycle, and the higher the instantaneous current, to maintain the average power level you've dialed. And the higher the current through a battery, the higher the losses in the battery's internal resistance.
So, strictly speaking, depending on your mod, you may increase battery life slightly by installing different resistance coils, simply by minimizing losses wherever they may occur. Lower resistance coils should be a bit harder on the battery and/or the mod. So unless the mod's voltage converter is highly inefficient at higher coil voltages, I'd say lower resistance coils should decrease the battery life slightly. In practice though, I don't think it matters all that much. But you might notice a difference if you're patient enough to try different coils and measure how long the battery lasts
