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volts/amps/ohms explained in detail on single and dual coil atty/cartos

Discussion in 'VV/VW APV Discussion' started by Krprice84, Mar 15, 2012.

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  1. Krprice84

    Krprice84 Senior Member Verified Member ECF Veteran

    there seems to be a little confusion and accidental mis-infomation being spread around here about how all of this works, and i'm sure most of it is simply by accident or because people have been misinformed or just misunderstand, as it really can get pretty complicated and hard to understand. i'll try to explain things in detail here but in an understandable way. if you have any questions or comments i'm happy to hear them and to answer anything you are wondering

    what some people have said on this board before, and what is the absolute end-all be-all truth, is that the ONLY thing that matters, in the end, is the wattage that you are putting through your coil(s). for these examples i'm going to list the ohms that the coil in the carto/atty, the voltage, amps, and watts. single or dual coil doesn't affect the wattage or amperage calculations when you use the equivalent resistance (ohms) of the dual coils. what i mean here is, if you have a 2 ohm rated dual coil carto, what you actually have are two coils that are each rated at 4 ohms, and that are wired in parallel. this means that EACH coil is acting as a single 4 ohm coil, and whatever voltage you are using on the carto will put amps through each coil as though each is a 4 ohm coil. the (simlified) reason that the coil gets rated at 2 ohms is because, when you have two coils in parallel, the current through the entire device is the sum of that through both of the coils (doubled that of one by itself). what this (in theory) would do is produce the amount of vapor that two separate coils would produce, albeit those coils would be ones that are rated at their individual resistance. one downside of this arrangement is that you only have so much surface area for the coils to heat up juice on, and to wick juice off of, and as such, you are more likely to have one (or both) coils not getting fully wet, all of the time, and thus, not producing at full potential. you also are getting less total wattage on each coil, thus producing cooler vapor, although more of it than just one coil rated at the same ohms.

    what this would mean is that a 2 ohm rated DC carto should produce a little cooler vapor than a 2 ohm rated single coil unit, though which one produces more vapor would be dependent completely upon the design of each unit and the thermodynamic properties of them. personally i don't recall all of the theory behind all of that, and as such, i can't remember if the hotter single coil should produce more vapor than the cooler dual coils, but i do know that it would also depend on the type of juice you are using (the mix ratio) and upon how wet they are etc. but since DC units are usually arranged vertically along the central axis of the carto, you can bet that both coils are not going to be constantly as wet (esp after a few puffs) as a single coil unit that is run either vertically, but at the bottom of the central axis, or horizontally at the bottom of the carto. this is because the juice is naturally going to tend towards the bottom of the unit, and thus, the top coil on a DC unit is going to get dryer quicker.

    now for some calculations: a 1.7 ohm coil that gets run at 3.5 volts draws 2.06 amps and generates 7.21 watts (which is turned into heat to vaporize the juice)
    now take a 2.8 ohm coil and run it at 4.5 volts, this coil will draw 1.607 amps and generates 7.23 watts
    these two coils, assuming they are built exactly the same, will produce EXACTLY the same vapor in every way, shape, and form. if they are identical in every way except for the resistance of the coil inside of them, they will be identical... there would be no difference in the heat of the vapor or the amount of it, because the wattage is the same, and thus the heat produced by each coil has to be the same.
    if you had a 2.2 ohm coil and put it at 4 volts, you would be at 1.81 amps and 7.27 watts; again, the same exact result as the two above.

    this proves that the common misconception that you can't get the same vaping experience from an LR as you can from an SR is just that, a misconception. the only thing that could make an LR give a better experience (from a VV PV) is a better inherent design of the atty/carto. otherwise, you are really better off going for an atty/carto that will be the highest resistance that you can use while still giving you the maximum possible current IF you set your PV at it's highest voltage. this will allow for the MOST flexibility (in that, you can lower the voltage down from max and realistically utilize MUCH more of the voltage range) whereas if you were to use an atty that maxes out the current (2.5 amps for many PV's) at only 4 volts, for example, then you are getting nowhere by setting the PV higher than that, because the unit will kick in it's current limiting function and force the voltage down to the point where the current stays at or below 2.5 amps. this will give you less options, as you can only go between 3 and 4 volts, instead of being able to go between 3 and 6 volts.

    hope this helps everyone

    p.s. i am an electronic engineering technologist and, as such, have a fair bit of experience and background in this topic...
    • Like Like x 1
  2. dekalbave

    dekalbave Senior Member Verified Member ECF Veteran

    Thanks for that very useful and informative post. I have to admit, that while I knew that wattage was the most important thing, I had no idea how they calculated the resistance of a dual coil carto.

    BTW, do you think both coils will stay wetter in a tank system? I just bought a couple of 1.5 ohm DCT's for use on my Provari, so I know I won't be using HV, but we'll see how it tastes and vapes.
  3. woodsy

    woodsy Full Member

    Mar 5, 2012
    United States
    Great post. I believe a fundamental understanding of Ohm's law is an absolute requirement if one is going to step up to anything higher than a starter kit. One important thing to note though is that while everything you said is correct, the one major variable here is the juice. Different combos are going to react differently to different systems. Having used both dual coils and singles I can tell that some like the lower yet more evenly distributed heat created by a dual coil system. Some that I have used prefer a single coil and provide a great throat hit. So while on the face of it the math does work out that they can provide the same experience you absolutely must try both systems on the same juice and then make a decision.

    I really do like your point though about how many people are limiting the range of thier VV device by going with Dual Coil for the implied benefit. That range also make a world of difference in how the vaping experience is perceived by many users.

    GREAT POST! Sticky?
  4. Johnny2puffs

    Johnny2puffs Moved On

    Oct 9, 2011
    This is why I said the DC was a fad. Come and gone. Not many vapers knew that the heat per coil is halved. The heat is the important component.
    Dual Coil 2 ohm you are vaping 4 ohm per coil. Just too little heat for me. A 3ohm single coil is the highest I would go for.
    At best for me is 2,5 ohm single coil or 1.25 dual coil but I haven't seen them around yet.
  5. dekalbave

    dekalbave Senior Member Verified Member ECF Veteran

    I got my DCT's from Totally Wicked today, and filled one with a particular juice I'm very familiar with. Now, on a SC Boge 3 ohm carto I was fine at 4.7volts, which is about 7.6watts. Withe the DCT, which is 1.5 ohm and I'm guessing a Smoktech, I need to push the voltage up to 3.9volts to get the same warm vapor and flavor, which is 10.1watts. So now I'm thoroughly confused, if a watt is a watt. Or maybe I didn't get the entire implications of the original post.
  6. Krprice84

    Krprice84 Senior Member Verified Member ECF Veteran

    Glad my post helped some people out! Like i said, it can be some confusing crap to figure out and understand... that's for sure. as someone else has said though, if you want to go beyond starter kits and stock voltage settings, you really do need at least a basic understanding of this stuff if you want to get the most out of your mod, otherwise you're going to end up wasting time and money chasing ghosts...

    dekalbave -

    yes, i would suggest that a tank will definetly help keep your dc coils wetter, but i've found one problem that i don't know for sure how to fully allieviate when using a tank/dc setup: while a tank DOES keep the coils wetter, you are still going to run into the problem where the juice gets into the carto from the tank through the slots/holes which are in the BOTTOM of the carto, and as such, isn't going to soak the top portion of the carto nearly as much. i'm finding that a tank definetly helps bigtime, but i CAN notice a slight difference in taste after the first bunch of puffs (at the point where the top area starts getting slightly less wet) - it's not horrible, but it is a little noticable. its still a whole helluva lot better than with no tank, thats for sure. on higher voltage settings though, i would suggest that the problem is going to get much worse as the heat goes up, or if the viscosity of the juice goes up (aka more VG in your juice).

    one possible solution to this problem is making an extra hole (or two) about half way up the carto, so that the juice can get in there as well. this MAY end up letting too much juice into the carto though, satuating it and possibly causing it to leak out the air holes. the other issue with this solution is that once the tank gets down below the level of the higher hole, you're going to just get the problem back again. i'd say that if you keep a dc carto on lower voltage levels and use a tank (and just use the standard position for the slots/holes), then you'll probably be pretty good... especially with juices that have less VG in them. any other ideas to help fix this issue?

    woodsy -

    yes, you are absolutely correct about the juice being an incredibly important part of the whole thing... a part that i don't fully understand yet, but you are right, it does seem that some juices don't like dual coil setups as much and vice versa.... i'm finding that the juices i usually use with a lower voltage are ones that work great with a dual coil setup... i get similar taste on a dc if i up the voltage, but a great deal more vapor volume, which makes sense considering there are two coils vaporizing instead of one...on juices that need higher voltage/heat levels to taste their best, i'm finding dc carto's just don't cut it, as they dry out too quickly in some areas (due to the higher heat level) and end up tasting burnt after a short while
  7. wyetterp

    wyetterp Super Member Verified Member ECF Veteran

    Jan 4, 2012
    Murrells Inlet, SC
    A boge 3ohm single coil, on a provari, will out perform any duel & triple coil. No matter the resistance. I've tried them all. Boge single coils out perform them all. Soon the vendors in the states will start getting the 45mm boge single coils that fit the dc tanks. I have some coming from heathcabin that are in customs now.

    To me there's really no advantage to duel or triple coils. I just don't think they've made a battery yet to safely push them to there full potential.
  8. dekalbave

    dekalbave Senior Member Verified Member ECF Veteran

    I'm starting to think that myself.
  9. Johnny2puffs

    Johnny2puffs Moved On

    Oct 9, 2011
    Just remember this. A 3ohm single coil is the same as a DC 1.5ohm heat wise or watt wise.

    For best you need 8 watts. This I have read here.
    Single coil of 3ohms to get 8 watts:
    3 times 8 = 24
    Square root of 24 = 4.9volts
    This is the best voltage for that atty.

    Dual coils of 2.5 ohms = 5 ohms total. So:
    5 times 8 = 40
    Square root of 40 = 6.3 volts
    This is the best voltage for that atty.

    If you want more heat than 8 watts then simply change the 8 to 9 as above then you get 9 watts.

    Now this should be stickied so I can remember it.

    This is just plain manipulated Ohms Law from a plain sparkey.
  10. mikebabs

    mikebabs Senior Member ECF Veteran

    Aug 22, 2011
    new jersey
    To my mind, this post should be a sticky.....I love cutting through all the muck and misinformation that is spread on this board, mostly unintentional, and, needless to say, all the cash people waste trying out new stuff only to be disappointed.
    We need large Boge 3.0 ohm cartomizers that FIT in large DCT tanks....
    VENDORS are you listening??????
  11. BoiseMike

    BoiseMike Senior Member ECF Veteran

    Apr 9, 2009
    Boise, ID USA
    I just got some Boge 3 ohm XL cartos from my local vendor that are working great in my Smoketech tank. Had to peel the black sticker off. No biggie. Cut a big slit in the bottom with my Dremel. I was afraid I'd gone too large with the cut, but I don't think that's possible. These things just eat up the juice, performing very well at 5 - 5.4 volts. Boge Cartomizer
  12. mikebabs

    mikebabs Senior Member ECF Veteran

    Aug 22, 2011
    new jersey
    Great to hear that BoiseMike.....healthcabin has some in stock too.....just a little spooked that they are in China....I have had some bad experiences with stuff coming from there....WAY too long a wait.....
  13. MickeyRat

    MickeyRat Vaping Master Verified Member ECF Veteran

    Mar 4, 2011
    Hickory, NC
    I'm not entirely convinced that watts are the whole story. It's true in theory but, if that were the case, there wouldn't be much point in varying the voltage, you could just vary the resistance to get the same effect. If you use a 1.8 ohm atomizer from a premium vendor like IKV at around 3.7 V and a 2.5 ohm atomizer from the same vendor at around 4.3 V, you'll be pretty close on wattage but, the experience will be a bit different. I use both of those configurations just about evey day.

    I think the reason for this is that the coil in the lower resistance atty is going to have a different sufface area than the higher resistance atty. Therefore to dissipate the same energy it will have to be a different temperature.

    You can think of it like burners on a stove. If you set them so that a large burner is using the same amount of energy as a small burner, the small burner will have to be hotter to dissipate the same energy.

    That's not to say that watts aren't a good rule of thumb. They are. You can get pretty close that way. I just don't think they are the whole story.
  14. BoiseMike

    BoiseMike Senior Member ECF Veteran

    Apr 9, 2009
    Boise, ID USA
    Good points. I don't know how they achieve the different resistances. A longer length or thinner gauge to increase it? A thicker gauge or shorter length to decrease it? Idunno. As much as I try to make a science out of it, it still seems to come down to a subjective "What do I like?" kind of decision. Why I like it and how it got there don't matter so much to me.
  15. MickeyRat

    MickeyRat Vaping Master Verified Member ECF Veteran

    Mar 4, 2011
    Hickory, NC
    We'll the only way to get lower resistance is to have less coils in which case the LR atty will have less surface area or use heavier gauge wire in which case the LR atty will have more surface area. I haven't taken apart an atty to find out and I don't intend to. However, I have gone both ways and I like the higher resistance atty at higher voltage better. I have a technical degree too and the OP is 100% right in theory and if this was a circuit, it wouldn't make any difference but, it's not and there is a difference.

    Regardless, you're right. It really comes down to what you like.
  16. dekalbave

    dekalbave Senior Member Verified Member ECF Veteran

    Thanks for the explanation. I tried asking that in a pevious post in this thread, but didn't get any response - until now. It also makes sense to me, given my experience with SC and DC cartos and the exact same juice in them. The DC cartos definitely seem to need more wattage to get the same flavor. At least for my tastebuds, anyway.
  17. Johnny2puffs

    Johnny2puffs Moved On

    Oct 9, 2011
    On a DC, you need double the wattage. ie
    If 8 watts is a good vape on a SC then a DC will need 8 watts on each coil for the same taste. So you need more volts on a DC than a SC.

    8watts on SC 3 ohm
    Volts needed = square root of 8 times 3
    = 4.9v

    8watts on each DC 2 ohm coil
    Volts needed = square root of 8 times 4 (each coil is 4ohm)
    = 5.6v
  18. Johnny2puffs

    Johnny2puffs Moved On

    Oct 9, 2011
    I retract all my posts above. Just got my LavaTube and found very strange things that goes against all what I said above.
    My old Leo at 3.7v tasted like I was smoking a rolled up newspaper. Now I got this LT and the same carto or atty with the same juice tastes great at 3v. If I go higher it gets that burning taste. So now what?
    Seems like the Leo bat cannot supply the amps to the coil and drops the voltage.
    Any suggestions?
  19. MrWarspite

    MrWarspite Super Member Verified Member ECF Veteran

    Supporting member
    Mar 20, 2012
    North Carolina
    The small ego/leo batteries really only push ~3.7v fresh off the charger and quickly start falling off. The lava/vari tube will stay at the dialed in voltage as long as there is juice left in the battery because of the boost circuit in the mod. That being said, you want to recharge your battery when it drops to 3.5 to extend the life of you battery.

    The beauty of variable voltage is finding the sweet spot in your juices. That is a big part of the discussion here. Every juice is different and will taste different at varying heat loads. For instance, kick bass vapor's Morning Dew. On my varitube with a 2 ohm boge tastes great at 3.8v. You get all the lemon lime flavor and that solid cola effervesence. Step up to 4.1 and the lemon-lime completely dissapears.

    Dual coils dont work well on mod's with protection circuits because the mod see's the total resistance of the coil's and dials down to protect you from overloading the coil. This works great in single coils but really sucks in dual coils. If you take the max amperage(2.5 on a lava/vari tube) of the pv times the ohm's of your cartomizer you get the max voltage the protection circuit will allow through. So we know a 3 ohm coil on a tube can take 7.5 volts (3 ohm x 2.5 amp) before maxing out. A dual coil with 3 ohm coils shows as 1.5 ohm to the protection circuit. This gives us 3.7 v as the max, (1.5 ohm x 2.5 amp). Those 2 coils arent getting near the voltage they need to create the same amount of heat on a single coil.
  20. MickeyRat

    MickeyRat Vaping Master Verified Member ECF Veteran

    Mar 4, 2011
    Hickory, NC
    That really depends on the mod. The Lavatube has a pretty low amp limit at 2.5A. Both the Provari and Buzz Pro have protection circuits and claim a 3.5A limit. However, there's a video on youtube that shows the Provari dropping out at 4.7V on a 1.5 DC. The Buzz went well over 5V.
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