You are correct in regards to the Sig, but if we're going to be totally accurate about just the Sig then let's also point out that it's maximum voltage is just 7V and that means that the Sig 150W can only safely hit 150W if you are using an extremely narrow range of atomizers. .17ohm to .327ohms. Any higher than .33ohms and you can't hit 150W no matter what you do. It requires too much voltage. Any lower than .17ohms and you're going to damage the batteries no matter what batteries you have since the amperage will exceed 30A.
The sig 150 can actually go to 7.5, so it lets you run at about 0.375 ohms if I remember right. If you want to be able to do the full 150w through the full charge cycle the mod allows(batteries down to 6.4v in series), you will have to build between 0.1 ohm(the minimum the mod will fire) and 0.27 ohms(6.4v output is the maximum it can put out when the batteries are at their cutoff, and that will give you 150w on a 0.27 ohm coil)
You're making a basic mistake here. You're trying to calculate watts based on amp and voltage alone without taking resistance into account. While that is possible if resistance isn't a factor, in an ecig resistance is ALWAYS a factor.
Resistance matters most on a mech mod. On a regulated mod, there are essentially two circuits, making resistance much less of a factor. The first is the input circuit between the battery and the chip. This is where it is going to draw the volts you are putting out at the amps you need to get the wattage you desire. The second circuit is the output circuit between the chip and the atomizer. This is where it is going to apply the proper voltage for the resistance of the coil to be operating at the desired wattage. The batteries never see the resistance of the atomizer. They are just putting out the wattage needed. The only time the coil resistance comes into play on a regulated mod is if it is within the operating parameters of the device, and if it is low enough to be able to output enough voltage to get the wattage you want. It wouldn't be an incredibly dumb idea, but since the circuits are separate, you could technically run 5amp CDR batteries in the thing with a 0.1 ohm coil if you are using very low wattage(under 30w). This would absolutely destroy the batteries in any mod where they were directly connected to the coil, but it won't in a regulated mod, because they never see the resistance of the coil. They just put out the amps needed at their current voltage to hit the desired wattage. At 20 watts, they would still only be running at 3.125 amps at 6.4v(the cutoff voltage). I would never suggest someone to try that, though. As soon as you try cranking the wattage up, the I specifically use my 20 amp batteries in it when I know I am going to run low wattage, because I know there is no harm in it. They never see the 0.1 ohm resistance, and when I am only running 50 or 60 watts, I am far below the 20 amp discharge they are rated at. This brings us into the next part of what you are saying:
For example, if you want to try to apply that 150W to a 2ohm coil you're going to need 17V. That's going to be pretty hard to do if your mod doesn't boost voltage, don't you agree? As I said before, you can't go any higher than .327ohms with a full battery charge, which will be bucked to the 7V maximum of the chip and the amp draw will be 21.41A. As soon as the voltage drops to 6.9V the wattage drops as well. It cannot deliver 150W to the .327ohm coil without boosting the voltage which as you said, the Sig cannot do. That means that the wattage drops and the amp draw is also REDUCED. The more the battery voltage drops the more the amps drop, because you cannot push 150W through that .327ohm coil without boosting the voltage.
On the flip side, let's say you're using that minimum safe resistance .17ohm coil. You can run it until the battery indicator says the batteries are fully drained because the voltage required to run that coil at 150W is just 5V and the chip needs a minimum of 6.2V just to operate. So it's never going to go over the 30A drain that it requires from the batteries, regardless of what the battery charge is.
Yo are right that you can't hit 150w with a 2 ohm coil. However, if you build a 0.2 ohm coil(within the safe parameters of the device), you can hit 150w throughout the entire range of the battery charge. This brings us to the next part:
So, the only way you're ever going to get over 30A drain on a set of batteries is to run an atomizer with the ohms so low and wattage so high that you're going to damage the batteries even with the best 30A batteries on the market at full charge.
You won't be able to go over 30 amps on the batteries, period. Even at 6.4v, at 30 amps, you would be putting out in excess of 180w.
At no time does the act of draining the batteries increase the amp load. If the combined battery voltage drops below 7V then the wattage and amp load will drop as well. It's impossible to maintain the wattage if the voltage drops and atomizer resistance remains the same, and it is impossible to increase the amp draw if both voltage and wattage have dropped.
As the battery voltage drops, the amp draw MUST increase to maintain the same wattage. If you build a 0.2 ohm coil, it can hit 150w from the full 8.4v the batteries put out all the way down to the cutoff of 6.4v. To hit 150 watts, it is going to have to draw however many volts the batteries are at a certain number of amps. At 8 volts(4v per cell), the batteries are each having to put out 18.75 amps. At 6.4 volts(the cutoff voltage of 3.2v per cell), the batteries are still going to have to put out enough amperage to hit 150 watts, meaning they are going to be putting out 23.4375 amps each. In this case, the amperage most certainly will increase as the voltage decreases. This holds true even with a 1 ohm coil running at 15 watts. At 8 volts, they will be putting out 8 volts at 1.875 amps. At 6.4 volts, they will be putting out 6.4 volts at 2.34 amps. Obviously, this low of an amp draw is no issue for the batteries.
Even the VTC series of batteries that everyone thinks of as 30 amp batteries are under a lot of strain after 20 amps. Mooch's tests clearly show this. If you are drawing 23.5 amps or more after the inefficiency of the mod, you are likely shortening the life of the battery more than you are when you are pulling the 21 amps from the battery when they are at 3.6v each.
