Thank you very much that info about the Mah makes it a bit more clear.
So, what sort of range are we looking at for a good battery for vaping?
I know I'll probably get a bunch of opinions on this one.
I see people building mods that run from 3.7 (ish) volts up to nearly 12.
From what i've read most of the manufacturers are running near the 3.7.
I also have read that anything under 3 just won't work.
The battery is where modders get to shine. A commercial ecig has to stuff an 8mm dia battery in their 9mm tubes, so they have to deal with about an AAAA sized cell, approximately 180 mAh capacity. It works, and millions are puffing away on them. But, the compromise they make is two fold.
First, you have to charge them frequently, because they are just too small for the job. Moving up to an AAA size roughly doubles your capacity, and an AA quadruples it. A Li-Ion 18650 is the largest commonly available single cell, and it weighs in at about a ten-fold increase in size and capacity.
Second, the commercial ecigs are extremely hard on their Li-Ions because the coils need to draw up to an ampere of current. That kind of current is tough on a 180mAh cell, shortening its life considerably. [Hard on most USB ports, as well.] A modder's cell of 750 mAh AA size (14500) can puke out 1 amp at intermittent intervals and barely compromise its maximum life.
So the cell you want is whatever you are happy carrying around. Like kina says, even lower energy-density NiMHs work fine, given that you use at least three of them, to boost their individual cell voltage of 1.2 v up to 'vaping voltage'.
The voltages are all over the place in modders forums, because coils vary so much in resistance, and atomizers in design. I've seen commercial coils at 4.5 ohms, and I just disassembled a DX cigar with a 1.2 ohm coil. It would take almost four times the voltage to heat a 4.5 ohm coil to the same temperature as a 1.2 ohm coil. The reason is that current determines the temperature of the coil, and it takes four times the voltage to push an amp of current through a 4.8 ohm wire as it does through a 1.2 ohm wire.
Commercial ecigs use microchips, some of which drive power switchers that can alter the voltage and current delivered, so you can't always strip the autoswitch and pcb out of a commercial, replace it with a push button, and always get the exact same performance out of the same atomizer and battery. A good rule of thumb is to measure the coil resistance, calculate what voltage will give you about an amp of current at the cell's peak voltage, and let the current fall off with the battery voltage as it's depleted.
Most Li-Ions have a nominal voltage of 3.7, with a peak voltage of 4.2, and cut-off at 3 volts. But a commercial ecig usually stops vaping properly at about 3.5 volts anyway, and their micro disables the cell at ~3.3 volts. So, for an example, if you used two Li-Ions in series, you would have a working range from 7.8 volts down to 6 volts, with a brief, fully charged voltage of 8.4. That is way too high for most atomizers, so you have to buck the current down to 5 volts or so, or whatever makes your coil and you happy.
