Physics:
The resistance of a given type and thickness of wire is proportional to the length of the wire. The number of coils is irrelevant to resistance, only the total length counts.
The resistance of different thicknesses of a given type of wire is inversely proportional to the square of the diameters. eg. if a given length of Kanthal Al 32 gauge wire (.20mm) has a resistance of 2.2 ohms then the resistance of the same length of 30 gauge wire (.25mm) will be 2.2 x (.20/.25) x (.20/.25) = 1.4 ohms. That's obviously a large difference in resistance between the thinner AWG 32 and the next available thickness which is AWG 30 wire.
The 2.2 ohms wire in the example could well be the resistance of Kanthal Al 32 (.2 mm) wire configured as a 7/6 wrap around a 2 mm wick. Which means that if you substitute the thicker 30 guage wire (.25mm) the resistance of the 7/6 coil would drop to 1.4 ohms. If that resistance proved to be too low for your application you would need to find a way of getting a greater length of wire into the device. Obviously, an 8/7 wrap would give about 1.4*8/7 = 1.6 ohms. That might suit you fine, but could you fit an extra coil into the device? An alternative would be to make bigger diameter wraps. If you changed from the 2 mm wick to a 2.5 mm wick, each wrap would now be 25% longer, and the overall increase in length of wire used would also be close to 25%. So, if the 7/6 wrap of 30 gauge wire around a 2 mm wick produces a 1.4 ohm coil, that could be increased to 1.4*2.5/2 = 1.75 ohms by using the thicker wick. There are minor errors in the calculations due to the fact that the length of the 2 leads has not been included but just looking at the the number and inner diameter of wraps is an excellent way to guestimate the outcome. You can also look at the specified resistance of different wire types and gauges - Kanthal Al 32 is near enough 45 ohms per metre and the 30 gauge is about 28 ohms per metre. So 50 mm of these wires would have resistances of about 2.25 and 1.4 ohms respectively. The 28 gauge wire is much thicker still and it is impossible to cram enough length of that wire into most devices but it is feasible for Genesis type atomizers for example.
So, what's all the fuss about resistance, why is it important? OK, very simple physics. Ohms = Volts/Amps; Amps = Volts/Ohms.
The higher the amps, the greater the heating effect. So, for a given device, if you increase the voltage you get higher current, more heat, and (maybe) better vaping. Alternatively, if you replace a higher resistance atomizer with a lower one you will get more current from the same voltage and again, maybe, better vaping.
But there are limits because all decent batteries have inbuilt protection of one type or another. I only use Joye twist batteries which provide variable voltage between 3.2v and 4.8v. If you use a 2 ohm resistance atomizer with one of these batteries it will work all the way through the range - low current at 3.2 volts, highest current at 4.8 volts, and you can find your own sweet spot anywhere in the range. But the protection seems to kick in at 2.4 amps, maybe a bit less. Put a 1.5 ohm atomizer on one of these and it works as expected to about 3.7v but twisting the voltage setting any higher achieves nothing. In fact there is very little good achieved by using a resistance lower than 1.8 ohms with this type of battery.
Coil Winding:
Once I have figured out the coil configuration that I want, ie how many wraps at what diameter, I always pre-wind the coil around a nail or similar solid object with the appropriate diameter. I also flame the wire first because that makes it easier to work with. I'm talking about silica wicks here. Then slip the coil off and twist the silica rope through in the direction such that it tends to reinforce rather than undo the weave. I tend to use 2.5mm or 3.0 mm rope in a 2.5 mm coil. It's very quick and easy.
Kanger T3 - I have been using the T3 for a couple of months now and it is my current PV of choice. I usually have 2 units on 2 twist batteries on the go at all times. Two other batteries are charging or on standby. I go through about 6 ml of juice a day and I have never experienced leaking problems which several people have complained about - no idea what I am doing right or what they are doing wrong. But I do have 2 issues. Firstly, the vape deteriorates noticeably after a couple of days as the wick gets clogged up. I used to do a cleaning ritual but now I just do dry burns till I see the coil glowing nicely. If that takes too long and/or the inner wick seems to be too clagged up I just rip the coil out and put it into the "recoiling" box.
So, this issue has now become a tolerable part of daily life. The second issue is that I occasionally make a new coil and find that it does not connect properly with the battery - that has even happened with a brand new coil. I've seen the problem reported by others, and read suggestions to pull up the battery head or pull out the positive connector pin slightly. Well, I'm not prepared to risk screwing up a great $25 battery to fix a problem with a $2 device. And I think that pulling the pin might be responsible for the leaking issue referred to earlier. So I experimented with a few ideas, nothing really satisfactory, until I decided to get some little magnetic disks. Perfect! Just got to be careful when refilling or recharging - little buggers will jump around and cling to anything which takes their fancy. Know people like that too. Oh yeah, I always put a few strands of wick on top of the coil after fitting an oversized one because theré always the danger of shorting the coil when you push the chimney back into the coil housing - it's never actually happened to me with 2.5mm coils (now my standard) but it did happen when I tried a 2.75mm wick - at least I think that was the problem.
And a really good tip specifically for T3 coils. First time I saw a video of somebody struggling to replace the little rubber grommet which separates the positive and negative leads I thought "I'll never be able to do that." And I was more or less correct - a nightmare of frustration. So my thinking became "got to figure how to secure the negative lead without pulling that rotten little grommet." It didn't take long - I remembered when an electrician was struggling to feed some new switch wires through a double brick wall - I got a short length of pipe and worked it through the hole and he fed the wires through the pipe with great ease. OK, perfect solution. I use a thin tube, actually a small gauge syringe needle, and push it through between the flange of the grommet and the coil housing. Then it's dead easy to thread the lead down the tube, gently remove the tube (making very sure it does not pull the grommet out with it) et voila!
Hope some of you guys find some of this useful.
The resistance of a given type and thickness of wire is proportional to the length of the wire. The number of coils is irrelevant to resistance, only the total length counts.
The resistance of different thicknesses of a given type of wire is inversely proportional to the square of the diameters. eg. if a given length of Kanthal Al 32 gauge wire (.20mm) has a resistance of 2.2 ohms then the resistance of the same length of 30 gauge wire (.25mm) will be 2.2 x (.20/.25) x (.20/.25) = 1.4 ohms. That's obviously a large difference in resistance between the thinner AWG 32 and the next available thickness which is AWG 30 wire.
The 2.2 ohms wire in the example could well be the resistance of Kanthal Al 32 (.2 mm) wire configured as a 7/6 wrap around a 2 mm wick. Which means that if you substitute the thicker 30 guage wire (.25mm) the resistance of the 7/6 coil would drop to 1.4 ohms. If that resistance proved to be too low for your application you would need to find a way of getting a greater length of wire into the device. Obviously, an 8/7 wrap would give about 1.4*8/7 = 1.6 ohms. That might suit you fine, but could you fit an extra coil into the device? An alternative would be to make bigger diameter wraps. If you changed from the 2 mm wick to a 2.5 mm wick, each wrap would now be 25% longer, and the overall increase in length of wire used would also be close to 25%. So, if the 7/6 wrap of 30 gauge wire around a 2 mm wick produces a 1.4 ohm coil, that could be increased to 1.4*2.5/2 = 1.75 ohms by using the thicker wick. There are minor errors in the calculations due to the fact that the length of the 2 leads has not been included but just looking at the the number and inner diameter of wraps is an excellent way to guestimate the outcome. You can also look at the specified resistance of different wire types and gauges - Kanthal Al 32 is near enough 45 ohms per metre and the 30 gauge is about 28 ohms per metre. So 50 mm of these wires would have resistances of about 2.25 and 1.4 ohms respectively. The 28 gauge wire is much thicker still and it is impossible to cram enough length of that wire into most devices but it is feasible for Genesis type atomizers for example.
So, what's all the fuss about resistance, why is it important? OK, very simple physics. Ohms = Volts/Amps; Amps = Volts/Ohms.
The higher the amps, the greater the heating effect. So, for a given device, if you increase the voltage you get higher current, more heat, and (maybe) better vaping. Alternatively, if you replace a higher resistance atomizer with a lower one you will get more current from the same voltage and again, maybe, better vaping.
But there are limits because all decent batteries have inbuilt protection of one type or another. I only use Joye twist batteries which provide variable voltage between 3.2v and 4.8v. If you use a 2 ohm resistance atomizer with one of these batteries it will work all the way through the range - low current at 3.2 volts, highest current at 4.8 volts, and you can find your own sweet spot anywhere in the range. But the protection seems to kick in at 2.4 amps, maybe a bit less. Put a 1.5 ohm atomizer on one of these and it works as expected to about 3.7v but twisting the voltage setting any higher achieves nothing. In fact there is very little good achieved by using a resistance lower than 1.8 ohms with this type of battery.
Coil Winding:
Once I have figured out the coil configuration that I want, ie how many wraps at what diameter, I always pre-wind the coil around a nail or similar solid object with the appropriate diameter. I also flame the wire first because that makes it easier to work with. I'm talking about silica wicks here. Then slip the coil off and twist the silica rope through in the direction such that it tends to reinforce rather than undo the weave. I tend to use 2.5mm or 3.0 mm rope in a 2.5 mm coil. It's very quick and easy.
Kanger T3 - I have been using the T3 for a couple of months now and it is my current PV of choice. I usually have 2 units on 2 twist batteries on the go at all times. Two other batteries are charging or on standby. I go through about 6 ml of juice a day and I have never experienced leaking problems which several people have complained about - no idea what I am doing right or what they are doing wrong. But I do have 2 issues. Firstly, the vape deteriorates noticeably after a couple of days as the wick gets clogged up. I used to do a cleaning ritual but now I just do dry burns till I see the coil glowing nicely. If that takes too long and/or the inner wick seems to be too clagged up I just rip the coil out and put it into the "recoiling" box.
So, this issue has now become a tolerable part of daily life. The second issue is that I occasionally make a new coil and find that it does not connect properly with the battery - that has even happened with a brand new coil. I've seen the problem reported by others, and read suggestions to pull up the battery head or pull out the positive connector pin slightly. Well, I'm not prepared to risk screwing up a great $25 battery to fix a problem with a $2 device. And I think that pulling the pin might be responsible for the leaking issue referred to earlier. So I experimented with a few ideas, nothing really satisfactory, until I decided to get some little magnetic disks. Perfect! Just got to be careful when refilling or recharging - little buggers will jump around and cling to anything which takes their fancy. Know people like that too. Oh yeah, I always put a few strands of wick on top of the coil after fitting an oversized one because theré always the danger of shorting the coil when you push the chimney back into the coil housing - it's never actually happened to me with 2.5mm coils (now my standard) but it did happen when I tried a 2.75mm wick - at least I think that was the problem.
And a really good tip specifically for T3 coils. First time I saw a video of somebody struggling to replace the little rubber grommet which separates the positive and negative leads I thought "I'll never be able to do that." And I was more or less correct - a nightmare of frustration. So my thinking became "got to figure how to secure the negative lead without pulling that rotten little grommet." It didn't take long - I remembered when an electrician was struggling to feed some new switch wires through a double brick wall - I got a short length of pipe and worked it through the hole and he fed the wires through the pipe with great ease. OK, perfect solution. I use a thin tube, actually a small gauge syringe needle, and push it through between the flange of the grommet and the coil housing. Then it's dead easy to thread the lead down the tube, gently remove the tube (making very sure it does not pull the grommet out with it) et voila!
Hope some of you guys find some of this useful.
