Coil Ohms

[CommaHolly]

OK, forgive me if I'm just being dense,,,,,,,but I just started using tanks a couple months back,,,so I'm a bit new at them,,,,

I've used a couple different kinds of tanks,,,,,,,,vivi Nova (smoktech), vivi nova (Vision), and Iclear 30 by Innokin,,,,,

I have used genuine coils for all of these except the Vision Vivi Nova,,,,,,those I got some off brand at the B and M.

so my question is this,,,,,,,

is it normal for the ohms of the coil to go UP over the time you use it??????

all my coils start at about 2.0 or 2.4 (depending on device),,,,,,,and go UP over the next month to two months that I use the coil until it's registering 2.6 for the coils that were originally 2.0,,,,,,,and 3.0 for the coils that were originally 2.4,,,,,,

regardless of brand, they have all done this,,,,,,,,,,,,,is this normal???

 

[SissySpike]

This is normal as sweeteners and and flavors build up a residue on you coils increasing the resistance it can jump a 10th from cold to hot. Look up dry burning. Ive never used those delivery systems other than just to try them but Its part of regular PM for those.

 

[Baditude]

It can and does happen. The cause is likely due to increased electrical resistance because the coil becomes gunked up with burnt juice. This is why some people will routinely clean their tanks and wicks and do dry burns of the coil to burn off the gunk. You can look on YouTube for your particular clearomizers and see a demonstration on how to do this, or....just replace the coil head with a new one.

 

[CommaHolly]

ok, but I DO clean and dry burn,,,,,,,like almost daily (I vape a lot,,,14ml a day and THAT was cutting back)

 

[Nataani]

Once a wire is tempered its resistance stays pretty consistent. Only external factors can then affect it, as those above said, soot buildup from different kinds of juices is the number one factor.

My best guess is that your not properly dry burning? I mean no offense, its just the only thing I can think of that could result in a 0.6 ohm difference. Even if you changed the shape of the coil a little bit when rewicking, I highly doubt it would change the resistance that much.

When dry burning make sure to blow on it from all sides, I typically pulse dry burn for at least a few minutes, making extra sure to blow down the center of the coil as well as from all other angles. I know some folks around here have gotten in the habit of using a small, stiff paintbrush, brushing down the coils after a dry burn to ensure a thorough clean. Personally, roasting and blowing on it seems to always work well for me.

 

[happydave]

heat will increase resistance, plain and simple. heating up a wire and letting it cool back down over and over again will increase resistance.
its a real battle for people that engineer space probes and satellites, things that see extreme hot and cold cycles.

 

[CommaHolly]

No offense taken,,,,,

that's why I asked,,,,,,I might be doing something wrong,,,,

so either I'm doing something wrong,,,,,,or maybe I just use it too long, and the constant heating is causing the problem,,,,,

I don't dry burn for a couple minutes,,,,,,so maybe that's the problem?? I'm going to try dry burning for longer,,,,

 

[happydave]

No your doing everything right it's just the nature of the beast. How many thousands of times do you fire a coil in a month?

 

[CommaHolly]

No your doing everything right it's just the nature of the beast. How many thousands of times do you fire a coil in a month?

if I had a penny for every time, I think I could retire

 

[happydave]

if I had a penny for every time, I think I could retire

exactly your heat cycling a coil thousands of times, and that's going to increase resistance. you can try cranking up the voltage a bit, to compensate for the increase in resistance.

 

[Nataani]

heat will increase resistance, plain and simple. heating up a wire and letting it cool back down over and over again will increase resistance.
its a real battle for people that engineer space probes and satellites, things that see extreme hot and cold cycles.

Apologies if I hijack the thread a bit here.

I was very curious about this, and have done a fair bit of research to try and confirm or deny whether a thermal cycle will increase the resistance of a wire over time. After flipping through all my books, and a fair bit of google-fu, I have found no evidence, either for or against. Do you have any sources to prove this claim, that a thermal cycle will increase the electrical resistance of a wire over time?

From a material engineering perspective. When a wire undergoes its first few thermal cycles, which happens during the rolling process in its manufacture, the crystal structure of the metal is determined. At this point the structure has stabilized. Subsequent thermal cycles will result in an eventual return to the same crystal structure after cooling and the subsequent relaxation period, resulting in the same resistance it originally had.

Granted, this return takes time, it is not as simple as when the wire reaches room temperature the structure has returned. This is the same reason why heating the wire will make it more malleable, and allow it to retain its shape once molded. When you heat the wire, the structure relaxes, even after returning to room temperature it remains somewhat relaxed. This increased malleability allows you to easily shape the wire. However, over time the wire returns to its original structure, losing that malleability, and retaining the memory of the shape you made. This, I can find sources for. So I propose that if the effect of a thermal cycle on malleability is nil, then the effect of a thermal cycle on resistivity should also be nil, as both rely on the atomic structure of the metal in question.

 

[generic mutant]

Why would gunk increase resistance?

The physics of this is totally beyond me, but someone hopefully will come along who understands it.

Naively, electricity travels through the wire. If you put gunk between the wire and the terminals, you increase resistance. You can put as much gunk as you like on the surface of the wire - it isn't in the circuit, so the only effect will be to insulate it thermally, which obviously will change the way its resistance changes under power, but shouldn't change the baseline.

 

[happydave]

Why would gunk increase resistance?

The physics of this is totally beyond me, but someone hopefully will come along who understands it.

Naively, electricity travels through the wire. If you put gunk between the wire and the terminals, you increase resistance. You can put as much gunk as you like on the surface of the wire - it isn't in the circuit, so the only effect will be to insulate it thermally, which obviously will change the way its resistance changes under power, but shouldn't change the baseline.

electrons MOSTLY flow across the surface of the wire. lets say i have a 2 gauge wire that is made of one solid length of copper and for comparison i have 2 gauge wire that is made up of 10 strands of wire. the multi stranded wire will have a lower resistance than the solid wire because of its increased surface area. so i could see how covering the wire with a substance COULD impede the flow of electrons. i have no idea if "e-liquid gunk" would cause this. but i have a pretty good way of finding out...

 

[happydave]

Apologies if I hijack the thread a bit here.

I was very curious about this, and have done a fair bit of research to try and confirm or deny whether a thermal cycle will increase the resistance of a wire over time. After flipping through all my books, and a fair bit of google-fu, I have found no evidence, either for or against. Do you have any sources to prove this claim, that a thermal cycle will increase the electrical resistance of a wire over time?

From a material engineering perspective. When a wire undergoes its first few thermal cycles, which happens during the rolling process in its manufacture, the crystal structure of the metal is determined. At this point the structure has stabilized. Subsequent thermal cycles will result in an eventual return to the same crystal structure after cooling and the subsequent relaxation period, resulting in the same resistance it originally had.

Granted, this return takes time, it is not as simple as when the wire reaches room temperature the structure has returned. This is the same reason why heating the wire will make it more malleable, and allow it to retain its shape once molded. When you heat the wire, the structure relaxes, even after returning to room temperature it remains somewhat relaxed. This increased malleability allows you to easily shape the wire. However, over time the wire returns to its original structure, losing that malleability, and retaining the memory of the shape you made. This, I can find sources for. So I propose that if the effect of a thermal cycle on malleability is nil, then the effect of a thermal cycle on resistivity should also be nil, as both rely on the atomic structure of the metal in question.

its does not return to its original structure. when most things are heated they expand, and do not fully contract when cooled back to the original temperature. (keep in mind that i say most things because somethings contract when they are heated) the only way you could get it to return to its original structure is to heat it up to a specific temp and hold temp for a length of time (anneal) or possibly cyro treat it at very specific temperature. but just heating it up to a random temperature over and over and expecting it to return to its original structure is absurd from a scientific prescriptive.

even with out temperature variance, a conductor can change its structure. look up " Tin Whiskers"

 

[generic mutant]

electrons MOSTLY flow across the surface of the wire. lets say i have a 2 gauge wire that is made of one solid length of copper and for comparison i have 2 gauge wire that is made up of 10 strands of wire. the multi stranded wire will have a lower resistance than the solid wire because of its increased surface area. so i could see how covering the wire with a substance COULD impede the flow of electrons. i have no idea if "e-liquid gunk" would cause this. but i have a pretty good way of finding out...

Maybe I'm just picturing it wrong (the quantum world famously resists visualisation through familiar, macro-scale analogies).

But to the extent that I can see juice gunk actually getting into the surface of the wire, rather than just forming a cake on top of it, I can't see cleaning it making much difference, unless you're actually scraping a layer of metal off the wire when you clean it (and I suspect most of us aren't).

If you paint a bare wire, does it increase the resistance? (not that paint = juice gunk, but I can't really think of an obvious way to test without heat cycling the wire, which presumably is the other major factor...)

 

[generic mutant]

The other thing nobody has mentioned is oxidation / corrosion between the wire and the terminals.

Dissimilar metals can corrode in contact,

https://en.wikipedia.org/wiki/Galvanic_corrosion

and electricity will arc between imperfect contacts, creating a layer of oxides.

How much of that you wash off in your cleaning process I have no idea, but I can't imagine it being much unless you're *very* thorough.

-edit

Maybe when people dry-burn, the important thing is the temperature the wire reaches, not cleaning juice gunk off the surface?

Reaching a temperature it doesn't reach in normal use may alter its physical structure. May also have an effect on the points of contact with the terminals, displacing the oxides or something...

 

[happydave]

Maybe I'm just picturing it wrong (the quantum world famously resists visualisation through familiar, macro-scale analogies).

But to the extent that I can see juice gunk actually getting into the surface of the wire, rather than just forming a cake on top of it, I can't see cleaning it making much difference, unless you're actually scraping a layer of metal off the wire when you clean it (and I suspect most of us aren't).

If you paint a bare wire, does it increase the resistance? (not that paint = juice gunk, but I can't really think of an obvious way to test without heat cycling the wire, which presumably is the other major factor...)

some compounds could increase resistance of a wire if applied to the surface of a wire. you would just cover the wire with the substance / paint , allow it to dry and then check it with a DVOM. no need to heat cycle it.

 

[generic mutant]

What I'm saying is presumably the three major things that happen to a coil in use are

1) Heat cycling
2) Layer of gunk on the surface
3) Corrosion / oxidation of contacts

If you want to work out which ones are effecting its conductivity, you need to test them independently. Painting it without heat cycling it, or heat cycling it without the presence of anything to adhere to the surface, would be obvious (though flawed) simple tests...

 

[happydave]

You misunderstand - what I'm saying is presumably the three major things that happen to a coil in use are

1) Heat cycling
2) Layer of gunk on the surface
3) Corrosion / oxidation of contacts

If you want to work out which ones are effecting its conductivity, you need to test them independently. Painting a wire might be a simple test...

i see what your saying. corrosion is a possibility. but you would notice any significant amount. and even if there was an amount that was not visible electricity would take the easiest path around it.

 

[generic mutant]

It's interesting stuff though, this vaping physics malarkey.