Calling BS on dual coils!

[Myk]

Myk, what wire gauge are you using for the 2 ohm coil and what gauge for the 3 ohm coil?

I've never set out to build a 3Ω for vaping as a single.
I know I didn't like 3Ω from stock PT or Vivi-Nova heads (2.5Ω or 2.8Ω?), getting too far above 2Ω in gennies and drippers and then using 3Ω coils in duals for 1.5Ω.

I've tried 30, 32 and 34 in the dual gennie which I do at 1.5Ω. When I was using mesh in it I'd burn them in separate but I can't say for sure which I vaped separate at 3Ω.

I've settled on .5x.1 ribbon for everything.

Why, do you have any suggestions?

 

[turbocad6]

wow, awesome thread. I see a lot of good info here so I'm not going to debate what many of you guys have already touched on. instead I'm going to say that I see many are focusing on 2 or 3 variables and making judgments based on those, but there are many more variables that all affect the end result. some less significant but others very significant, yet I don't see them being factored in much or at all here.

#1 is airflow. a build may run too "hot" in one atty, and I use that term loosely, yet run perfectly well in another and the difference can be as simple as air flow and type of draw(volume of air moved). this can of course affect everything from vapor production to flavor, and also burning of the wick vs wicking great. the coils are cooled, or more accurately the coils temp can be limited somewhat buy both juice exposure(wicking) and airflow. there is a huge difference between sipping air for a mouth hit through a relatively tiny air hole vs doing a heavier lung hit with larger airflow opening(s) there can also be a huge resulting difference in firing time to achieve a satisfactory "hit" a 20w vape that takes 3 seconds will use less power than a 10 watt vape that get's hit for 9 seconds. in a case like this the 20w vapor may get more run time than the 10 watt vapor overall, depending on yet another variable which is the power source itself

#2 is chamber volume VS coil volume = flavor produced. what I'm saying here is that chamber size has one of the largest affects on the actual flavor you get, and this to is influenced somewhat by airflow. this is why a tiny chamber atty can taste wonderful with a single coil yet a much larger chamber will taste much better with multiple coils and/or longer coils. this topic alone is huge and is very related to the coil differences being discussed here

#3 is surface area/ohms per inch relationship. what I'm saying here is that 3 twisted 32 gauge wires may equal the resistance of a single 28 gauge(hypothetical for illustrative, not actual) yet the 2 will have a very different affect on flavor production. the uneven surface area of the twisted will give you much more surface area per ohm than an equivalent single smooth wire coil. it is also adding facets orifices and pockets that also heavily influence flavor and vapor production and this is something that is independent of resistance, yet related too

#4 is coil mass/wicking ratio, this is a factor that is determined by wire gauge(and profile when twisted wire comes into play) vs coil diameter and the resulting internal wick diameter and wicking material AND wick density, compared to the overall length of the coil(s). many believe that a larger coil will always wick better than a smaller diameter coil but this may or may not be true, again depending on other variables and actual wicking design, whether a gennie or a tank or a BF squonker .

really the bottom line is everything affects everything else and there are way more variables than just the basic ohm, wire size/mass and voltage, add to that many of the curves are not linear

really this is an incredibly deep topic and I could type on and on for days repeating much of what's already been said and debating also much of what has been said, but instead I decided to just inject these 4 additional variables that I personally think are up there on the high influence list of variables because I see to many judging by just accounting for a few variables without considering the many others. these 4 that I added are very significant in this discussion I think, and that's not to say there aren't many others, stuff ranging from coil orientation compared to airflow and air path to the internal resistance of the battery and the resulting voltage drop under load compared to the actual load. this is a very deep topic indeed and I'm afraid it can wind up being debated forever, which is actually a good thing because combining knowledge will always result in more knowledge gained. the original post title set some guys off and appeared to be ignorant to the many other variables that do come into play here, without factoring in all the variables it is just ignorant to say dual coils are bs. I'm NOT saying the OP is ignorant, only that the one short sentence title is such a loaded statement that will be true in some situations while not being true in others

 

[John_]

wow, awesome thread. I see a lot of good info here so I'm not going to debate what many of you guys have already touched on. instead I'm going to say that I see many are focusing on 2 or 3 variables and making judgments based on those, but there are many more variables that all affect the end result. some less significant but others very significant, yet I don't see them being factored in much or at all here.

#1 is airflow. a build may run too "hot" in one atty, and I use that term loosely, yet run perfectly well in another and the difference can be as simple as air flow and type of draw(volume of air moved). this can of course affect everything from vapor production to flavor, and also burning of the wick vs wicking great. the coils are cooled, or more accurately the coils temp can be limited somewhat buy both juice exposure(wicking) and airflow. there is a huge difference between sipping air for a mouth hit through a relatively tiny air hole vs doing a heavier lung hit with larger airflow opening(s) there can also be a huge resulting difference in firing time to achieve a satisfactory "hit" a 20w vape that takes 3 seconds will use less power than a 10 watt vape that get's hit for 9 seconds. in a case like this the 20w vapor may get more run time than the 10 watt vapor overall, depending on yet another variable which is the power source itself

#2 is chamber volume VS coil volume = flavor produced. what I'm saying here is that chamber size has one of the largest affects on the actual flavor you get, and this to is influenced somewhat by airflow. this is why a tiny chamber atty can taste wonderful with a single coil yet a much larger chamber will taste much better with multiple coils and/or longer coils. this topic alone is huge and is very related to the coil differences being discussed here

#3 is surface area/ohms per inch relationship. what I'm saying here is that 3 twisted 32 gauge wires may equal the resistance of a single 28 gauge(hypothetical for illustrative, not actual) yet the 2 will have a very different affect on flavor production. the uneven surface area of the twisted will give you much more surface area per ohm than an equivalent single smooth wire coil. it is also adding facets orifices and pockets that also heavily influence flavor and vapor production and this is something that is independent of resistance, yet related too

#4 is coil mass/wicking ratio, this is a factor that is determined by wire gauge(and profile when twisted wire comes into play) vs coil diameter and the resulting internal wick diameter and wicking material AND wick density, compared to the overall length of the coil(s). many believe that a larger coil will always wick better than a smaller diameter coil but this may or may not be true, again depending on other variables.

really the bottom line is everything affects everything else and there are way more variables than just the basic ohm, wire size/mass and voltage, add to that many of the curves are not linear

really this is an incredibly deep topic and I could type on and on for days repeating much of what's already been said and debating also much of what has been said, but instead I decided to just inject these 4 additional variables that I personally think are up there on the high influence list of variables because I see to many judging by just accounting for a few variables without considering the many others. these 4 that I added are very significant in this discussion I think, and that's not to say there aren't many others, stuff ranging from coil orientation compared to airflow and air path to the internal resistance of the battery and the resulting voltage drop under load compared to the actual load. this is a very deep topic indeed and I'm afraid it can wind up being debated forever, which is actually a good thing because combining knowledge will always result in more knowledge gained. the original post title set some guys off and appeared to be ignorant to the many other variables that do come into play here, without factoring in all the variables it is just ignorant to say dual coils are bs. I'm NOT saying the OP is ignorant, only that the one short sentence title is such a loaded statement that will be true in some situations while not being true in others

Pretty much everything I wanted to say but am too tired to type.

 

[turbocad6]

and that's only a small fraction of what I've wanted to add to this thread since it began but I can't type for days and days and people hate a wall of text too

 

[Ryedan]

wow, awesome thread. I see a lot of good info here so I'm not going to debate what many of you guys have already touched on. instead I'm going to say that I see many are focusing on 2 or 3 variables and making judgments based on those, but there are many more variables that all affect the end result. some less significant but others very significant, yet I don't see them being factored in much or at all here.

~~~ Big snip ~~~

Yup, when I said to emus something like 'then it gets complicated', the points you listed were what I had in mind and I know that's not all of em. There are too many variables to be able to put the whole picture together with the data we have.

I have a background in plastic injection molding. That process also has a bunch of interlinked variables and was considered quite the art for many decades. Finally someone took the time and put in a lot of effort to get a handle on it all and it has become quite the science now.

We know the variables, what we need is for someone to do the engineering work to define everything numerically so it can be worked with. Until that happens all we can say is that if you change N in direction Y you will get more of D, but we don't how much more and we don't know what happens if you also change two other variables.

Now, unlike plastic molding no one is making a living from the act of vaping, so no ones livelihood will be improved by figuring this stuff out. That means IMO it will take a long time before anyone puts in the work to define everything.

 

[Ryedan]

I've never set out to build a 3Ω for vaping as a single.
I know I didn't like 3Ω from stock PT or Vivi-Nova heads (2.5Ω or 2.8Ω?), getting too far above 2Ω in gennies and drippers and then using 3Ω coils in duals for 1.5Ω.

I've tried 30, 32 and 34 in the dual gennie which I do at 1.5Ω. When I was using mesh in it I'd burn them in separate but I can't say for sure which I vaped separate at 3Ω.

I've settled on .5x.1 ribbon for everything.

Why, do you have any suggestions?

I was thinking you were probably using thinner wire for the higher resistance coils. I made a spreadsheet a little while back to figure out coil surface area and power per square inch of coil. Yes, I was bored that day

I think you're running regulated mods so I modeled the top three lines for that. If you use thinner wire for the 3 ohm coils and maintain the same power per coil by changing coil lengths and PV voltages this is what happens to watts per square inch assuming your mod can output the amps required:

The bottom four lines are my Trident running dual 1 ohm coils (each coil, so 0.5 ohms combined) and my single coil AGA-T, both on mechanical mods. The voltages I entered are after voltage drop of about 0.4V. The watts per square inch are really high on the AGA-T, but I'm using SS mesh which I think acts as a heat sink so not all of that power is making vapor.

I have no idea about ribbon wire as I have not used it.

So this is looking at watts per coil area only and of course all the other atty variables are still in play also. Just wanted to toss this at you as data that might be relevant to why you don't like higher ohm coils. I have no proof whatsoever that this has any validity, I just think it may.

The most important takeout from all this for me is if you want to try keeping watts per square inch down, changing wire size has a significant influence. As always, YMMV.

 

[Myk]

I was thinking you were probably using thinner wire for the higher resistance coils. I made a spreadsheet a little while back to figure out coil surface area and power per square inch of coil. Yes, I was bored that day

I think you're running regulated mods so I modeled the top three lines for that. If you use thinner wire for the 3 ohm coils and maintain the same power per coil by changing coil lengths and PV voltages this is what happens to watts per square inch assuming your mod can output the amps required:

The bottom four lines are my Trident running dual 1 ohm coils (each coil, so 0.5 ohms combined) and my single coil AGA-T, both on mechanical mods. The voltages I entered are after voltage drop of about 0.4V. The watts per square inch are really high on the AGA-T, but I'm using SS mesh which I think acts as a heat sink so not all of that power is making vapor.

I have no idea about ribbon wire as I have not used it.

So this is looking at watts per coil area only and of course all the other atty variables are still in play also. Just wanted to toss this at you as data that might be relevant to why you don't like higher ohm coils. I have no proof whatsoever that this has any validity, I just think it may.

The most important takeout from all this for me is if you want to try keeping watts per square inch down, changing wire size has a significant influence. As always, YMMV.

I wasn't thrilled with the thinner wire for anything. If nothing else the coils didn't last. But I really couldn't control burning with them.
I think it's how it all works together with me. The way I draw, the air resistance I want, the time to heat up I want and the flavor I want.

I should be covered for watts per inch. The ribbon makes a solid wall on the gennie coils. That much surface heating turns the wicks into heating elements.

 

[edyle]

So...uh...what's the bs on dual coils???

The BS on dual coils are Blowing Smoke

 

[Ryedan]

I wasn't thrilled with the thinner wire for anything. If nothing else the coils didn't last. But I really couldn't control burning with them.
I think it's how it all works together with me. The way I draw, the air resistance I want, the time to heat up I want and the flavor I want.

I should be covered for watts per inch. The ribbon makes a solid wall on the gennie coils. That much surface heating turns the wicks into heating elements.

Well, I think the burning with thinner wire is probably because of the higher watt density and limited air flow. And for me thicker wire is also more physically robust which I like specially in Genys so I can take out the wick, clean it and put it back without destroying the wire.

And yes, all the other variables come into play also . I'm going to have to try out some ribbon wire sometime. The problem is I'm pretty happy with round wire so there's not much incentive for me to go there, but that can change too

 

[edyle]

I haven't started experimenting with dual coils yet, but it's all about surface area, right? Well I built a 3.1 ohm 1.85 mm ID microcoil in my Squid the other day. It's easily twice as big as any other microcoil I've built yet. I have to run it close to 6 V for anything to happen, but when it happens, it's pretty assertive.

Question: Running a variable regulated mod, what is the practical differences in the vapor quality between using a length of wire to wrap one coil, and using the same length of wire to wrap two coils and run them in parallel?

The mass and surface of the coil would be the same, and setting the mod to roughly the same power, I would think that the surface temperature would be similar as well. The only differing thing I can think of is wicking, is that right? Now if you wrap the single coil on a slightly larger ID...

If you set the same power level, then you'll ................ hmmmm
lets see:
2 ohms of wire; 1 2 ohm coil; 4 volts;
power = 4x4/2 = 8 watts;
current = 4/2 = 2 amps

2 ohms of wire: 2 1 ohm coils: power = 8 watts
resistance= 0.5 ohms
voltage = sqrt(8 x 0.5) = 2 volts
current = 2/0.5 = 4 amps total aha! but 2 amps per coil! So same current through each segment of wire as before.


Yup, correct, temperature should be same. The dual coil would be a quarter the resistance, and the voltage you'd be using would be half the voltage.

 

[edyle]

This whole thing about coil temperature is I believe misunderstood by a lot of people.

As long as you have enough power to start vaporizing juice, coil surface temperature does not vary because of power applied.

It only goes up if the wire is not wet enough.

Thoughts anyone ...

For a particular coil, one wattage will produce 1 temperature of the dry coil.
Yes it is correct that the actual working temperature of the coil while the wick is wicking, is going to be lower, but the wattage sets an upper limit to the temperature.

 

[edyle]

I have a question about coils in general. I've been reading here that lower resistant coils produce more vapor. I use a Protank 2 and 1300ohm Vision Spinner. The coils it came with were 1.8 & 2.0 but they couldn't stand up to dialing my Spinner up past about 3.7 and they burnt out. I like my Voltage up to at least 4 V & sometimes 4.3V but after burning many expensive coils over the past 11 months, my go to coils are at least 2.5V. I get great vapor production and taste- but am always open to more. Great clouds of vapor are half the fun of vaping. So did I just get bad coils and should I be able to use the 2.0 ohm coils at 4 V?

Sent from my NX008HD8G using Tapatalk

1:
Lower resistance coils will burn more power from the same battery compared to high resistance coils.

2:
a 2 ohm coil at 3.7 volts burns 3.7x3.7/2=6.8 watts.
a 1.8 ohm coil at 3.7 volts burns 3.7x3.7/1.8=7.6 watts
a 2.5 ohm coil at 4 volts burns 6.4 watts

if the coils get dry they'll pop.

I can dryburn my coils safely at 3 watts and they glow red without risk of popping; thats about sqrt(3x2)=2.4 volts

 

[Ryedan]

For a particular coil, one wattage will produce 1 temperature of the dry coil.
Yes it is correct that the actual working temperature of the coil while the wick is wicking, is going to be lower, but the wattage sets an upper limit to the temperature.

Yes of course, you are absolutely correct edyle .

I don't want to vape a super hot, dry coil, so I do my best to stay away from that. I keep the coil wet and work with coil temps that make my vape safe.

 

[edyle]

the whole point of dual coils is to get more power to vape more juice, at low voltage.

 

[rurwin]

Precisely. Or re-worded, the whole point is to get more power at the same voltage, (because you're using a mech mod.)

It works like this: You find the coil you love. Two of them will be just as good but deliver twice the vapour, if you can drive them the same.

If you can supply twice the current, you can put the two in parallel and give them the same voltage: V = 2I R/2, 2W = V 2I
You use twice the power and you get twice the clouds.

If you can supply twice the voltage, you can put the two in series and give them the same current: 2V = I 2R, 2W = 2V I
You use twice the power and you get twice the clouds.

In both cases, each coil sees the same voltage and current as it did in the original case where it was by itself.

A special case of putting the two in series is to make a single coil of twice the size, but that will make the wicking and airflow different and you may find the coil you love is now giving you dry hits and burning.

As a corollary, if you start from the big coil and try to split it into two, then that also changes wicking and airflow but you are working blind in trying to correct it. You may well decide that this whole dual coil business is BS.

 

[da_dyno]

my buils is at 0.24

 

[el Jexican]

Got to figure your 1.3ohm dual coil is just two 2.6ohm single coils. Can't really compare that to a 1.3ohm single coil for perfomance. A more comparable wiuld be a .65ohm dual coil set up which would with out a doubt out perform the 1.3ohm single coil.

 

[Myk]

Precisely. Or re-worded, the whole point is to get more power at the same voltage, (because you're using a mech mod.)

It works like this: You find the coil you love. Two of them will be just as good but deliver twice the vapour, if you can drive them the same.

If you can supply twice the current, you can put the two in parallel and give them the same voltage: V = 2I R/2, 2W = V 2I
You use twice the power and you get twice the clouds.

If you can supply twice the voltage, you can put the two in series and give them the same current: 2V = I 2R, 2W = 2V I
You use twice the power and you get twice the clouds.

In both cases, each coil sees the same voltage and current as it did in the original case where it was by itself.

A special case of putting the two in series is to make a single coil of twice the size, but that will make the wicking and airflow different and you may find the coil you love is now giving you dry hits and burning.

As a corollary, if you start from the big coil and try to split it into two, then that also changes wicking and airflow but you are working blind in trying to correct it. You may well decide that this whole dual coil business is BS.

Except it doesn't work like that.

Two 1Ω coils in parallel, or a .5Ω dual does not vape the same as a 2Ω coil or two 1Ω coils in series. I even have my doubts whether a 2Ω coil or two 1Ω coils in series vapes the same.

It may sound good in electrical theory but a 1Ω dual atty being the same as a 1Ω single atty needing the same voltage and vaping the same also sounds right according to electrical theory.
A 2Ω 34ga coil does not vape the same as a 2Ω 28ga coil no matter what the electrical theory says about it.
There is more going on here than electricity.

 

[rurwin]

Except it doesn't work like that.

Two 1Ω coils in parallel, or a .5Ω dual does not vape the same as a 2Ω coil or two 1Ω coils in series.

You've tried that on 7.4V? I said that the 2Ω coil would be different.

I even have my doubts whether a 2Ω coil or two 1Ω coils in series vapes the same.

So do I. It's a matter of having half the number of wicks and lower airflow.

It may sound good in electrical theory but a 1Ω dual atty being the same as a 1Ω single atty needing the same voltage and vaping the same also sounds right according to electrical theory.

But they have different wicking and airflow.

A 2Ω 34ga coil does not vape the same as a 2Ω 28ga coil no matter what the electrical theory says about it.
There is more going on here than electricity.

Right. A 28ga coil of the same resistance will have more turns or larger diameter. The two have different wicking and airflow.

Experimenting with parallel coils is easy; just use the same voltage. But experimenting with series coils is much harder because we don't have mods that can vary the voltage over the required range. Added to which, series coils need a different geometry in the atomiser. You can't lay them out like parallel coils in an RDA or you will have a long lead between them. They should work, but it would be a challenge to get them to work without mods and atomisers built with them in mind. I think that the best use of them will be to adapt sub-ohm microcoils in RBAs for use with VV/VW mods. Using them in RDAs will change the airflow too much.

There's an advantage to series coils that may make it worth the hard work of investigating them: they don't make batteries vent.

 

[edyle]

my buils is at 0.24

Do you vape at 0.24 ohms?

On that setup here is my question:
What ohm would you describe as a short on that setup?