Well, I pretty much got my questions answered, and maybe the OP did also.
Thanks.
If you use 0.5 ohms or above, and can reproduce the coil resistance to 4% or so (+/- 0.02 ohms), then you shouldn't have any trouble making and testing subohm coils. The somewhat low, but positive, temperature coefficient of resistance for Kanthal alloys allows low current (at just a few milliamps) resistance testing with less than one percent error compared to normal vaping current and temperature (wet coil).
The coil resistance meter (constant current source and voltmeter) is a cheap way to wind coils over and over repeatably. At $20, or less, it sounds like a nice tool to own and could save you a few headaches. A lot less trouble than firing up a HP3478A just to measure e-cig coils. The typical 3 1/2 digit multimeter is a waste for low resistance measurements. A few 1% or better resistors from someplace like digikey would also make a nice cheap addition to a 'coil lab'.
ICR protected cells (at least 18650 please), good ones with 2 or 3 mosfets on the protection board, not the cheaper single mosfet boards that would trip at 3 amps or so, sound like they should handle intermittent currents up to 5 or 6 amps. That should safely handle the 0.7 to 0.8 ohm subohmers without tripping out all the time (full charge trip on current limit), unless you are boosting output to above native cell voltage. Of course you have to put up with another 25 milliohms or so in the current path because of the Mosfets. Any good IMR 18650 should be able to handle 10 amps and cover the 0.5 ohm and above vapers.
Few vapers consider the power lost in the mod itself. Even regulated mods which might give you a constant vape, chew up battery power. Usually more as the coil or carto resistance is lower. That might be noticeable trying to get as many hits as possible from a charge. Go below 0.5 ohms and you could be losing 30% or more of your watt hours in the mod itself if every contact in the total current path isn't spiffy clean. A good quality purely mechanical mod with a loop resistance of 0.05 ohms (that's actually pretty darn good), and a 0.2 ohm coil would waste 20% in just the mod. Some of that in just the 510 connection.
Sound like I got that right?
I've done several 'twice pipe' mods with dual 1.5 ohm DCCs. While not the same hit wise, the mod and cell don't know the difference between four 3 ohm coils in parallel and a single 0.75 ohm coil. You might, but the mod/cell won't. Now, if you went to parallel 18650 cells, or a 26650, the cells will feel much better in the morning
Here's a few twice pipe, 0.75 ohm capable homemade mods I found on the internet.
