Voltage drop... I know what it is, but why is it important to consider?

[CloudZ]

Hopefully this thread doesn't make anyone too angry.

Okay, so we all know that voltage drop in a mech comes from internal battery resistance and mod resistance, mostly in the connections, and to a lesser extent the atomizer resistance in any place other than the coil. It translates to a small fraction of the coil resistance which has more negative (parasitic) influence as coil resistance decreases. Less voltage going to atomizing the juice and more wasted heating up the mod needlessly.

What I don't understand at this time is why this matters. I can see lower "voltage drop" making the mod more efficient, meaning more of the power supplied by the battery makes it to the coil, and thus you can use a slightly higher resistance coil and get the same vape quality while draining the battery more slowly. Let's say I don't care about battery life and I just want to get the most intense vape possible.

The sticking point for me is, I run into wicking deficiency long before I run into coil temperature deficiency. At around 0.6 ohms on a single coil, I may or may not start burning my juice. This is despite the probability that my unmodified KTS has significant internal resistance. Wicking seems to be the big challenge. I've tried several different wick setups: cotton from 1mm to 4mm in diameter fitting perfectly in the coil, allowing a slight amount of expansion as it saturates. 2mm to 6mm of normal silica fitting exactly inside the coil with very little squeeze. Perfectly wrapped 28 gauge kanthal with a small amount of spacing, lots of spacing, or no spacing (microcoil or touching coil). I can't get to 0.5 ohms on a single coil without burning juice. At this point I feel like my airflow and wicking is about as good as I can get it with the materials I am currently using.

So if I am already vaping sub-ohm coils, am I just unable to get sufficient wicking and that is why voltage drop seems irrelevant? Or is it really only relevant for multi-coil builds where wicking is less difficult? I can see how it is relevant on a carto or something like that, but if I can control the resistance in an RBA and I get sufficient wicking, why not just build a lower resistance coil and disregard power loss?

Please enlighten me. I don't intend to challenge the concept, I just want to know if someone has a good explanation I can learn from. And sorry about the essay.

 

[Baditude]

PBusardo on sub ohm vaping, "Sometimes, just because you can, doesn't mean you should."

That's all I'll say on the matter. Excuse me for not attempting to answer your questions.

 

[minimalsaint]

PBusardo on sub ohm vaping, "Sometimes, just because you can, doesn't mean you should."

That's all I'll say on the matter. Excuse me for not attempting to answer your questions.

Not a big fan of PB but I have to agree with this logic. I fell like too many people are going sub-ohm without even knowing why.
In my own experience, lower ohms lead to higher drop, but the resistance makes up for the power loss. I'm no expert so that's about all I can contribute.

 

[st0nedpenguin]

The last couple posts up there ^ just explained why getting as much battery power to the coil as possible is a good thing.

If you like vaping at a certain wattage and can hit that mark with a higher ohm coil because your device is more efficient, it's kind of a no brainer.

 

[dr g]

Hopefully this thread doesn't make anyone too angry.

Okay, so we all know that voltage drop in a mech comes from internal battery resistance and mod resistance, mostly in the connections, and to a lesser extent the atomizer resistance in any place other than the coil. It translates to a small fraction of the coil resistance which has more negative (parasitic) influence as coil resistance decreases. Less voltage going to atomizing the juice and more wasted heating up the mod needlessly.

What I don't understand at this time is why this matters. I can see lower "voltage drop" making the mod more efficient, meaning more of the power supplied by the battery makes it to the coil, and thus you can use a slightly higher resistance coil and get the same vape quality while draining the battery more slowly. Let's say I don't care about battery life and I just want to get the most intense vape possible.

The sticking point for me is, I run into wicking deficiency long before I run into coil temperature deficiency. At around 0.6 ohms on a single coil, I may or may not start burning my juice. This is despite the probability that my unmodified KTS has significant internal resistance. Wicking seems to be the big challenge. I've tried several different wick setups: cotton from 1mm to 4mm in diameter fitting perfectly in the coil, allowing a slight amount of expansion as it saturates. 2mm to 6mm of normal silica fitting exactly inside the coil with very little squeeze. Perfectly wrapped 28 gauge kanthal with a small amount of spacing, lots of spacing, or no spacing (microcoil or touching coil). I can't get to 0.5 ohms on a single coil without burning juice. At this point I feel like my airflow and wicking is about as good as I can get it with the materials I am currently using.

So if I am already vaping sub-ohm coils, am I just unable to get sufficient wicking and that is why voltage drop seems irrelevant? Or is it really only relevant for multi-coil builds where wicking is less difficult? I can see how it is relevant on a carto or something like that, but if I can control the resistance in an RBA and I get sufficient wicking, why not just build a lower resistance coil and disregard power loss?

Please enlighten me. I don't intend to challenge the concept, I just want to know if someone has a good explanation I can learn from. And sorry about the essay.

If you are burning your juice with a given coil wire size, go to a bigger size. Using what you have now try maybe twisted 28.

 

[CloudZ]

The last couple posts up there ^ just explained why getting as much battery power to the coil as possible is a good thing.

If you like vaping at a certain wattage and can hit that mark with a higher ohm coil because your device is more efficient, it's kind of a no brainer.

Is it really a no brainer? I am missing the reasoning here. All I am understanding is that you can get more vape time from a more efficient mod. However, no one really brings this up as a key point when discussing voltage drop. They just talk about how it "hits harder".

If you are burning your juice with a given coil wire size, go to a bigger size. Using what you have now try maybe twisted 28.

Gahhh... You're right. For some reason I was thinking that 28 gauge is thick enough to push lower than 0.6 ohms, but I guess that's wrong. I may try twisting it at some point; that's why I got some 28 gauge after I twisted some 32 gauge. Untwisted 32 starts burning at 1.4 ohms for me, and untwisted 30 around 1.0. I suppose it makes sense that 28 would do the same at 0.6. Pretty obvious now that you mention it.

 

[dr g]

No it's not a no brainer. Technically high resistance, small-wire coils are the most efficient as far as getting vapor from power since they heat up with so little power. But they give very little surface area and thus can only vaporize so much juice at a time.

Juice burns at the same temperature no matter what coil you are running. The point of wide gauge coils is to have a larger coil-wick package which can vaporize more juice at a time, making a bigger cloud. However, it takes more power to run the larger coil.

As for voltage drop, in general the less the better, but note there are two sources of voltage drop. One is the design of the battery itself, some are prone to less voltage drop when hit with high loads than others. Depending on the type of mod you are using that can be a consideration in the performance equation. The other is resistance from the device, which in general is plain inefficiency -- the less the better because the power is doing nothing by being lost in the mod's internal resistance.

 

[Rader2146]

[snip]

So if I am already vaping sub-ohm coils, am I just unable to get sufficient wicking and that is why voltage drop seems irrelevant?

[snip]

This seems to be the main issue. You are already at maximum performance for the wick, reducing the voltage drop will only serve to make things worse.

If the goal is intense vapor and flavor...fix the wicking and then you can turn up the power. You didnt mention the atty or wick that you are using, but if it's SS mesh you'll have a very hard time feeding a .5Ω coil.

 

[CloudZ]

This seems to be the main issue. You are already at maximum performance for the wick, reducing the voltage drop will only serve to make things worse.

If the goal is intense vapor and flavor...fix the wicking and then you can turn up the power. You didnt mention the atty or wick that you are using, but if it's SS mesh you'll have a very hard time feeding a .5Ω coil.

I agree, but I don't see how I can improve wicking beyond what I already get. As I admitted in my second post, I have been thinking that 28 gauge should be good for lower than 0.6 ohms, which is probably wrong.

I currently have 2 rebuildable drippers, a Chyclone and a Phoenix V3, both with air holes drilled out to 1/16". I wick with normal 2mm silica (torchable, at least) and cotton yarn. I've tried SS/silica hybrids without much success, they start out great but quickly start clogging and spitting badly. So yeah, my wicking materials aren't the high-dollar silica or ceramic fiber type, but I can't justify spending so much per foot on what amounts to imported heat resistant rope.

 

[CloudZ]

I just want to thank everyone for their input. After reading and thinking about it for a while, I think I get it now.

Less voltage drop not only means more efficient battery usage, but also the ability to run coils that are a little bit higher resistance and a little safer. This also means a little bit more coil surface area, so an improved vape with that safer coil. And, if you want to push the limits of your battery's current output, you can get a little bit closer to theoretical calculations (using appropriately heavy wire, of course) in the real world. My perception of wicking limitations was likely incorrect, and I am probably overheating the coil and burning juice that way.

 

[dr g]

It depends how you achieve the higher resistance, if longer wire then yes more surface area, but if smaller wire size then the opposite.

 

[Rader2146]

Sorry, I just caught the original version of your second post and missed the edit. I quit using 28g when I went below .7Ω. I like to keep at least a 3/4 wrap with the coil and change the wire size to suit. I've been using .5Ω's of 26g with #10 cotton crochet yarn on an IGO-L. I tried 2mm and 3mm German braided silica and they just weren't cutting it. They were good for the first few hits after dripping, but fell off fast and burnt quick. The cotton saturates much better and gives me a fair warning that I need to refill before it burns. At a few dollars for 100+ yards of yarn, it's easy for me to justify. The 26g coils also last forever. I pull the yarn, dry burn and rinse, then re-wick and it's good as new. One is 3 months young and the resistance and performance hasn't changed a bit.

 

[CloudZ]

It depends how you achieve the higher resistance, if longer wire then yes more surface area, but if smaller wire size then the opposite.

I mean for a given wire diameter, you can add a wrap for more surface area and get the same wire temperature as one less wrap on a less efficient mech. This is just an example, I know it wouldn't work out exactly this way.

 

[CloudZ]

Sorry, I just caught the original version of your second post and missed the edit. I quit using 28g when I went below .7Ω. I like to keep at least a 3/4 wrap with the coil and change the wire size to suit. I've been using .5Ω's of 26g with #10 cotton crochet yarn on an IGO-L. I tried 2mm and 3mm German braided silica and they just weren't cutting it. They were good for the first few hits after dripping, but fell off fast and burnt quick. The cotton saturates much better and gives me a fair warning that I need to refill before it burns. At a few dollars for 100+ yards of yarn, it's easy for me to justify. The 26g coils also last forever. I pull the yarn, dry burn and rinse, then re-wick and it's good as new. One is 3 months young and the resistance and performance hasn't changed a bit.

Thanks for describing your experiences, this makes a lot of sense and helps confirm what I've learned about 0.6 ohms being too low for 28 gauge. Same thing with the silica (although I don't have the fancy German stuff ), the first few hits are great but it quickly gets nasty after that. Cotton definitely wicks better, but if you burn it even once its garbage. The nice thing about silica is you can rinse and dry burn it clean, but that doesn't really matter if it tastes horrible after 3 hits. I generally stay above 0.8 ohms with my 28 gauge and silica to avoid this. I figured I was running into a similar limitation with the cotton at 0.6 ohms, but its probably wire temperature.

I could probably get the silica down to 0.6 ohms and the cotton down to 0.4 ohms with 26 gauge, but I probably wont just because I already have so much 32, 30, 28 and .8 ribbon that I need to use up. As I previously mentioned, I may try twisting the 28 to see how it works out.

 

[Alexander Mundy]

If you are looking for more surface area, try some of the things I have been playing with.

Still experimenting, but results with coil over 3 wraps of mesh over cotton with the first one and with the ugly uneven one further down have had good results.

 

[UncleChuck]

To be honest, I'm a bit confused by the OP's confusion.

Just to make sure, you are aware that higher voltage gives more power? And inversely, lower voltage gives less power? I just wanted to be clear, since if you know that, you kind of answered your own question.

People get into sub-ohm vaping for higher power than traditional setups can provide, and near instantaneous heat-up times. If you are building a setup specifically to get large amounts of power and quick heat-up time, isn't it obvious that loss in voltage is going to be an issue?

Asking why voltage drop is important is basically like asking why the voltage of your battery matters, or why the voltage setting on a VV device is important. Aside from the obvious drop in power, mechs with a high voltage drop will cause slower heating of the coil. I want to mention that I'm honestly not trying to be rude or condescending, I'm just not really getting the question I guess (or the answer is so obvious I'm thinking I MUST be misunderstanding the question)

As far as getting really really low resistance (under .6ohm) with a single coil, I'd suggest 26ga wire instead of 28. It's probably not a wicking issue but a surface area issue. Run a standard atty at 20 watts and you'll burn the heck our of your juice, pop the coil, or both. This is because they use such thin wire that you can't put too much power into them without the coil getting too hot.

28ga works great for 1.0ohm to .6ohm or so, but lower than that and you'll be running into the same issues you would running a standard atty at 20 watts, not enough surface area on the coil so the coil gets too hot burning your juice. Bumping your coil up to 26ga wire should allow you to drop a few more tenths of an ohm without burning juice. It's all about the relationship between surface area and power, too much power in too small a surface area and your temp gets too high.

Hopefully this was helpful in some way, and once again please don't take any offense to the first half of my post, I'm just trying to figure out where the confusion is coming from.

 

[CloudZ]

UncleChuck-

The answer isn't obvious, and I tried to explain why that is the case. I know exactly how this stuff works. The mistake I was making was falsely assuming that 28 gauge is as heavy as you need to go for any sub-ohm coil. I have no idea why that was stuck in my mind. So because my 28 gauge coil was burning juice at 0.6 ohms, I assumed it was a wicking issue. It probably isn't, the coil is probably just getting too hot.

Also, I don't think you read my post where I explained what I've learned here. You also just repeated that less voltage drop "hits harder" or "responds faster". Yes, for a given resistance, but why not just go lower ohms to make up for device losses? I also don't mean to be condescending, but take some time and think about it.

If extreme performance is all you are looking for and you have appropriately thick wire, voltage drop will only seriously impede you at your battery's amp limit. You are using up everything your battery can safely give you, so every volt that can get to the coil counts.

 

[bapgood]

I think this thread delves into the answers you are looking for http://www.e-cigarette-forum.com/fo...-not-matter-its-all-about-wire-temp-read.html

 

[UncleChuck]

UncleChuck-

The answer isn't obvious, and I tried to explain why that is the case. I know exactly how this stuff works. The mistake I was making was falsely assuming that 28 gauge is as heavy as you need to go for any sub-ohm coil. I have no idea why that was stuck in my mind. So because my 28 gauge coil was burning juice at 0.6 ohms, I assumed it was a wicking issue. It probably isn't, the coil is probably just getting too hot.

Also, I don't think you read my post where I explained what I've learned here. You also just repeated that less voltage drop "hits harder" or "responds faster". Yes, for a given resistance, but why not just go lower ohms to make up for device losses? I also don't mean to be condescending, but take some time and think about it.

If extreme performance is all you are looking for and you have appropriately thick wire, voltage drop will only seriously impede you at your battery's amp limit. You are using up everything your battery can safely give you, so every volt that can get to the coil counts.

I know you know your stuff quite well, which is why I was confused Which is also why I was worried about offending you, as it was not my intention at all to try to talk down to anyone, I just wanted to make sure "we were all on the same page" type of thing. You were on the right page and I was in the glossary somewhere trying to figure out the page number

I'm not the most graceful person when it comes to wording things and that can come off as rude sometimes, and I apologize if it came off that way. A weakness of language (and non face-to-face communication)

I think what also confused me was the talk of burning juice and 28ga wire, I just didn't see where all this jived into a single issue that was being discussed. There were two separate issues (.6ohms being too hot for 28ga, and the question of why you can't simply drop ohms lower to counteract voltage sag) Severe voltage sag means your battery is already at its limit, so lowering ohms isn't going to fix the issue. Maybe it mixed me up by trying to combine both of these issues into a connected problem. I don't know.

It seems like you got your answer from someone (I hope?) and basically it's a matter of not wasting the batteries energy if you don't have to. I have a GS Matrix Telescope that was horrible out of the box, and had a very large and apparent voltage drop compared to my other mechs. I did exactly what you describe, and ran a coil a few tenths of an ohm lower than my usual "sweet spot" (around .7-.8 ohms) This did slightly boost the performance, but heat-up time was still low, and I was running too close to the limits of the battery. The more you try to counteract the voltage drop by increasing current, the more pronounced the voltage drop will be. Kind of like a shoveling sand against the tide situation. Anyway now I'm rambling and probably being redundant (or confused again ) so I'll stop. Sorry again if I came off rude!

 

[CloudZ]

No problem at all, thank you for your input. I know how it goes with asking questions and giving answers on forums, sometimes its tough to guess what will offend someone or come off as rude because you can't judge facial expressions or body language. I am also sorry if I came off as rude at all.

But yeah, I totally get that if you are already hitting the limits of your battery, voltage drop kills you. I have some high drain 18650 IMR's, which I can push to 8-9 amps safely so 0.4-0.5 ohms is not out of the question. I don't want to go lower than that though.