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Thread: A simple wattage chart showing the relationship between voltage and resistance

  1. #11
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    Silica dripper, mesh genesis, air hole size, single or twin coil, wire gauge, wraps?

    Heads up, the next section's going to get complicated.
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  2. #12
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    Quote Originally Posted by Juzm View Post
    OK, question time. From what I can tell most mech modders like very low ohm coils from what I can gather. Scuse me if I'm wrong.

    I build higher ohm coils between 1.5 and 2.2 ohms for a longer draw on mechs.

    Low ohm coils (Approx 1 ohm or sub ohm for example) on mech mods taste like burnt shit to me unless I'm just pulsing the button like I would whilst oxidising a coil.

    Some input on this from the community and the OP would be greatly appreciated because you're such a great bunch.
    If you are on a genesis, then you probably aren't wicking well enough to cope with 12w+ over a long draw.... If you are on silica, i'd probably assume that you don't have enough surface area for the juice to get into. EG you are running dry during the long draw.

    It's all about wattage as the end result anyway... you could have a 1ohm coil, running @ 3.2v and be at 10.24w, or you could run a 2.5ohm coil @ 5.1v for 10.4w and taste REASONABLY similar, due to the power you are delivering to it.

  3. #13
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    Quote Originally Posted by Juzm View Post
    OK, question time. From what I can tell most mech modders like very low ohm coils from what I can gather. Scuse me if I'm wrong.

    I build higher ohm coils between 1.5 and 2.2 ohms for a longer draw on mechs.

    Low ohm coils (Approx 1 ohm or sub ohm for example) on mech mods taste like burnt shit to me unless I'm just pulsing the button like I would whilst oxidising a coil.

    Some input on this from the community and the OP would be greatly appreciated because you're such a great bunch.
    I don't use sub ohm coils on my gennies, I prefer a 1.1-1.2ohm coil but at present on my CVI I use a 1.4-1.5ohm coil because if it goes below 1.3ohms it doesn't like to fire.

    If you are using a sweeter vape juice, then yes it may taste burnt at lower ohms, on a mech mod but I find drier tobacco vapes shine more with the lower ohm coils & taste better.
    Oh & I used to chain vape, leaving the button firing for 10 - 15 seconds, when my old mech was working.
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  4. #14
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    This next bit isn’t newbie territory, but for those that are so inclined it is Part 1 of what I feel is a rather comprehensive view to help understand how the vapor production system works. These are my thoughts, so I welcome debate on this due to the number of methods variables that are inherent in the way we get juice to vaporise. For the newbies out there, don’t fret. Most of the variables have been taken care for you in simply your choice of clear or carto. For rebuildable users out there this should be a good read.

    Disclaimer: Keep in mind this is just a fire hose of what's in my head. There are probably going to be errors, omissions, generalisations, grammatical mistakes, and perhaps some things that are just plain incorrect.

    There are four key factors involved besides the electrical elements of a personal vaporiser. They are the coil, wick, air flow and juice.

    The simple view

    The coil

    The coil is of course at the heart of a personal vaporiser. Through being heated, it is responsible for vaporising the juice.

    The air flow

    The air flow is what allows plain air to pass by the juice-laden coil and reach your pie hole.

    The wick

    The wick is responsible for two things in a personal vaporiser. The first of these is getting the juice from the reservoir of juice into a position ready to be vaporised. The second is storing an amount of juice in close proximity to the heating coil.

    The juice

    A mixture of complex flavours and nicotine carried in a mixture of propyl glycerol and vegetable glycerine, that when vaporised by a hot coil allows you to get your sweet sweet nicotine.


    Additional topics
    Wattage
    Joye eGo and regulated output

    Vaporisation Theory - The Simple View
    - you are here now
    Vaporisation Theory - The Complex View: The Coil & Air Flow
    Vaporisation Theory - The Complex View: The Wick
    Vaporisation Theory - The Complex View: The Juice
    Amperage Theory
    Amperage Theory - Vamo, Smok Zmax v2, SVD, Provari v2 (coming soon)
    Last edited by luntingsir; 22-10-13 at 12:48 PM.
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  5. #15
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    The complex view

    The coil
    What we haven’t taken into account yet is the thickness of the coil and its configuration. A higher resistance can be achieved by either a thinner diameter wire or a longer wire. Conversely a lower resistance can be achieved by either a thicker diameter wire or shorter wire. Does it matter whether you achieve the given resistance by altering the thickness of the coil over the changing the length? Damn straight it does.

    Let’s start by having a thin wire to build our coil. As it is thin it is inherently higher in resistance, to achieve our given resistance we have to make it short. Because the wire is thin, it has a low level of thermal inertia, meaning that because there isn’t as much metal there, it heats up very quickly. That’s a good thing, because we don’t have to sit around waiting for our coil to heat up before it reaches the optimal temperature for vaporising juice. The downside however is that because it is short, it can only be wrapped around the wick a few times. This is an issue, because it isn’t in contact with much of the juice that’s been soaked up in our wick. In short, we’ve got a fast reacting coil, but it’s not covering the real estate that it could be.

    So, what about using a thick wire? Well as it is thick it is inherently lower in resistance, to achieve our given resistance we have to make it longer. Because the wire is thick, it has a high level of thermal inertia, meaning that because there is comparatively more metal there, it takes longer to reach the optimal temperature for vaporising juice. But, the good news is that “longer” only really means a second or so. The even better news is that because we have a longer length of wire to work with, we can wrap it around the wick more times, meaning it can be in contact with more of the juice that’s soaked on our wick. In short, we’ve got a coil that only takes a fraction longer to heat up, and is in close proximity to the maximum amount of juice on our coil.

    So regarding the design of coils, the best solution involves the thickest wire available that will give us the longest wire that can be comfortably fitted within the given build space.

    As an aside, this is why contact coils (aka microcoils) have been so popular recently, as they provide for the maximum amount of wick coverage for the given build space.

    The air flow
    The wonderful air flow that draws in plain air and deposits vapour in our lungs is also far more complicated than it first appears.

    Firstly, the rate of flow must agree with the user. Some like a loose draw, like drawing breath through a McDonalds straw, others like it tight like… like… like, sucking a golf ball through a hose. I knew a girl who could do that.

    Some like long lung draws, some like short mouth draws. Everyone’s different.

    Where it gets complicated is that the rate of flow, and to some extent the duration of the draw, has a direct effect on the heat of the coil. When the outside air gets drawn past the coil it has the effect of cooling the coil down. The higher the rate of flow, the greater the cooling effect on the coil. Too cool, and vapour production could suffer. But too little flow and the coil could heat up well past the optimal temperature for vaporisation and you could suffer from overcooked juice, burning wicks and oxidising coils. Bad.

    Let’s say that you and your mate Steve are using the same type of coil with the same resistance, you both supply the same voltage and use the same juice. The difference is that you like short hard loose draws, while Steve likes long slow tight draws. Because of the different draw preferences, you may find is that your preferred wattage is 9 watts, while Steve likes 7 watts. Most cartos and clearo, or just about any off the shelf atomizer will come with a fixed air path that cannot be widened or narrowed. So for clearo or carto users it’s worth trying a few to find the ones that match with your preference.

    But for the rebuilders out there we have a choice of varying our air hole. This choice will be largely dependent on whether you like a tight or loose draw, but the ramification is that it will also determine how much power you can deliver to your coil without it overheating. In high powered mech mods the coil (we’re talking for the sake of arguement 10+ watts, which is only a 1.8Ω coil @ 4.2V) if left unattended, will quickly overheat. If you go further, and are using a sub-ohm coil at 0.9Ω you’re pushing close to 20 watts. That means your coil is going to be super hot. The way cloud chasers combat this is with large air holes, much larger that those typically than those that come out of the factory. At this point you really have no option but to have a loose draw (unless you have serious sucking power) by using an air hole 1.5mm or larger. It helps cool the coil and also extract the vapour which is being produced at a very high rate.

    To finish off this section we’re going to talk about air holes. A key thing to note is that a 2mm air hole is not twice as big as a 1mm air hole. A 1mm air hole has an area of 0.79mm, whereas a 2mm air hole as an area of 3.14mm, almost 4 times the size. So the story here is that if you’re drilling out air holes do it in small increments to test the draw. It’s very easy to overdrill if you’re not being careful.


    Next time we’ll talk about the complex view of wicks and juice. I hope this has been interesting.


    PS: For the new vapers out there, this information is overkill. If you have any further questions, even about the most basic topics, keep them coming.


    Additional topics
    Wattage
    Joye eGo and regulated output

    Vaporisation Theory - The Simple View
    Vaporisation Theory - The Complex View: The Coil & Air Flow
    - you are here now
    Vaporisation Theory - The Complex View: The Wick
    Vaporisation Theory - The Complex View: The Juice
    Amperage Theory
    Amperage Theory - Vamo, Smok Zmax v2, SVD, Provari v2 (coming soon)
    Last edited by luntingsir; 22-10-13 at 12:48 PM.
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  6. #16
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    Conversely a lower resistance can be achieved by either a thicker diameter wire or shorter wire
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    Ignore the Super-moderator tag in my profile, I have resigned from that position but admin have not updated my profile as yet

  7. #17
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    Thanks, fixed.

    See, I told you there'd be errors.
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  8. #18
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    Quote Originally Posted by luntingsir View Post
    Silica dripper, mesh genesis, air hole size, single or twin coil, wire gauge, wraps?
    Mesh gennie, about 1mm, 20 or 32 AWG, 4-6 wraps.

    Quote Originally Posted by m0n4g3 View Post
    If you are on a genesis, then you probably aren't wicking well enough to cope with 12w+ over a long draw.... If you are on silica, i'd probably assume that you don't have enough surface area for the juice to get into. EG you are running dry during the long draw.

    It's all about wattage as the end result anyway... you could have a 1ohm coil, running @ 3.2v and be at 10.24w, or you could run a 2.5ohm coil @ 5.1v for 10.4w and taste REASONABLY similar, due to the power you are delivering to it.
    And answered already, thanks!
    luntingsir likes this.

  9. #19
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    Quote Originally Posted by Juzm View Post
    Mesh gennie, about 1mm, 20 or 32 AWG, 4-6 wraps.
    So my guess is that your first issue is too small an air hole for the wattage you're running at. I'd say a minimum of 1.3mm, but personally I run my gennys at 1.6mm. Without the necessary air flow the coil is simply overheating. The second is that because of the lack of air flow, not only is the coil overheating, but the wick itself is contributing to the issue. Mesh wicks are great, but they retain a significant amount of heat that can linger between drags. By the time you go to take your second drag you're already dealing with an overheating system. You may notice that after a drag that there is vapour coming out of the cap for some time simply due to the retained heat. This is the reason I find I can't run gennys (with a 1.6mm air hole) as high as I would with silica, I probably max out at 11-12 watts (at that's with a silica sheath) even though I can chain silica at 20 watts.
    Last edited by luntingsir; 23-07-13 at 12:18 AM.
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  10. #20
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    Great graph, well done luntingsir
    There are too many fantastic points I really like to list about what you wrote so I'll just chime in on a couple of other things to see if I can add to this post.
    Safe working voltage range is way below 3.4v, optimal min voltage is dependent on the battery and load etc. plus life expectancyy from number/depth of cycles vs age / storage conditions etc.
    working parameters of the power source eg ego won't get to 21.8watts, once you pass the 'working' parameters, it can work in reverse or die. You pretty much mentioned the above for the ego but I thought I would point it out again anyway.
    Nominal voltage is an average voltage of a battery through its power range. I used to know the standard for calculation but have totally forgotten right now and you have reminded me to find out again
    For Ohms, better include or at least take into consideration the internal resistance of the battery and the losses on the way to the coil. To be accurate with the wattage, you have to measure the voltage under load. The ECD does this nicely. You get to a point when lowering resistance, especially sub Ohm, where the power loss in the mod/battery can become significanr if you know what I mean, and you end up chasing the wrong tail if springs / contacts / cables / battery etc are collectivley creating high resistance etc.
    luntingsir, TheDishD and Duke916 like this.
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