coils and resistance vs heatup time

[jb783]

Hey folks,

just got a dripper that has four posts, letting me do dual coils.

I noticed if it's below one ohm it seems like it takes a while to heat up. I noticed this with twisted 28 gauge dual coils. While my untwisted 28 gauge dual coils, hitting about an ohm, heat up very fast.

Or does heat up time have nothing to do with ohms, but everything to do with length of the coils?

Another thing I noticed, below an ohm and the batteries drain very, very quickly.

basically are sub ohm builds really only useful on mech mods?

 

[TheGreatApe]

From what I can tell you, the larger the wire the more ramp up time there will be. Think about it like water through a hose. The bigger the hose diameter is(coil), the stronger the pump has to be (battery). The less resistance the more power it will take to heat up. I can't say this without mentioning to stay within your battery limits

Sub ohm coils are good on mechs as well as box mods. The box mods really make sub ohm'ing nice because they reduce ramp up time in larger coils.

 

[sparkky1]

What are you using for a mod and battery ?

 

[jb783]

It's a hana dna 30 clone (hcigar) it's got an 18650 2100mah in it.

 

[sparkky1]

Well you've got it backwards, the lower the ohm build the faster the coil will heat up ....

Have you ever seen this ? Coil wrapping | Steam Engine | free vaping calculators

 

[readeuler]

The coil lag is related to two things: Coil mass (which itself depends on wire gauge, coil configuration, and net resistance) and wattage.

Here's a hypothetical build similar to your quicker build: Coil wrapping | Steam Engine | free vaping calculators

I have no idea what wattage you're running at, I just assumed 30W. Notice the value for heat capacity: 29.54 mJ/K

Now here's a hypothetical build closer to your second: Coil wrapping | Steam Engine | free vaping calculators

Again I don't know the wattage, and this time I don't even know the resistance (it's very important here), so I just assumed 0.5 ohms, half the resistance of the first build. This time the heat capacity is approximately twice that of the other build, 59 mJ/K.

So anything you do to increase the mass (i.e., add resistance by adding wraps; using multiple coils in parallel (inclluding twisted wire) to decrease the resistance, or use thicker wire) will increase that heat capacity, which is a measure of how many watt-seconds you need to heat up the coil.

On a regulated mod, battery drain is only dependent on the wattage you've set (as well as the native battery voltage, but you don't have any control over that). Of course, if you find that your lower-resistance coil needs twice as long to heat up, you'll find that your battery drains twice as quickly.

I've got some insider information: State O Flux is working on a new blog post that addresses using the above calculator, Steam Engine, to keep coil lag under control. Stay tuned, and welcome to ECF!

 

[sparkky1]

What size are your wrapping tools ?

 

[Lessifer]

Well you've got it backwards, the lower the ohm build the faster the coil will heat up ....

Have you ever seen this ? Coil wrapping | Steam Engine | free vaping calculators

not necessarily. Lower resistance with the same gauge wire will heat up faster. Thicker wire takes longer to heat up though, more wire mass takes longer to heat.

 

[maxd]

more metal -> longer start time

 

[ignotus]

not necessarily. Lower resistance with the same gauge wire will heat up faster. Thicker wire takes longer to heat up though, more wire mass takes longer to heat.

And longer to cool.

 

[TheGreatApe]

Exactly. Having less resistance on a larger coil will allow the electricity to pass through freely, taking it longer to heat up. It is the resistance that causes the heat.

 

[jb783]

Well you've got it backwards, the lower the ohm build the faster the coil will heat up ....

Have you ever seen this ?Coil wrapping | Steam Engine | free vaping calculators

it's pretty cool but I don't really understand everything on it. Still learning.

 

[jb783]

Exactly. Having less resistance on a larger coil will allow the electricity to pass through freely, taking it longer to heat up. It is the resistance that causes the heat.

so this is what i'm seeing and I tend to agree with you

So, knowing this it would seem that:

1+ ohm gives faster ramp-up time, and uses less battery. Is that correct?

my next question naturally is, why do people sub-ohm then? Is it because it's too difficult to make cool coils +1 ohm? Having to use 28 gauge really is a pain.

 

[readeuler]

so this is what i'm seeing and I tend to agree with you

So, knowing this it would seem that:

1+ ohm gives faster ramp-up time, and uses less battery. Is that correct?

my next question naturally is, why do people sub-ohm then? Is it because it's too difficult to make cool coils +1 ohm? Having to use 28 gauge really is a pain.

The resistance is really a red herring here, but I'll talk about it a little bit.

For a single coil, two things matter for resistance. A larger gauge (smaller diameter of wire) decreases resistance, while a longer length of wire increases resistance. Atomizer coils are made from resistance wire, so they're technically resistors in a circuit. If you wire two resistors in parallel (dual coils, or using two strands of wire for a single coil), it halves the resistance. If you've got a dual coil with two strands of wire in each (dual twisted 28 gauge coils, for example), then your resistance is only 1/4 the resistance of a single strand of that wire.

So here's what's happening: many of the things that lower the resistance (thicker wire or multiple strands) increase the mass of metal that needs to be heated, hence the crazy coil lag. This could happen with really thick wire with an abnormally high resistance (if you made a 1+ ohm single coil from beefy 24ga, for example).

So, resistance is kind of a bad proxy for coil lag: sometimes more resistance means more mass, sometimes less resistance means more mass (more mass = more coil lag at a fixed wattage).

With a regulated device, resistance is also completely irrelevant for battery life (unless, of course, coil lag forces you to take abnormally long draws, but that's not exactly 'interesting').

With a mech, amperage (rate of battery drain) depends on resistance: amperage I = V/R, voltage over resistance. Dividing by a smaller number means more amps.

But with a regulated device, displayed wattage is the only thing you can control that affects amperage (battery life); the resistance is irrelevant and that's why I said it's a red herring. Your battery voltage is what it is; if your DNA is hitting the coil with 5 volts, or 3 volts, that's probably not the actual voltage of the battery.

In this situation, the amperage I = (Displayed wattage) / (Actual battery voltage [not displayed voltage]). So more wattage means quicker battery discharge, or when your battery is running low.

Don't worry too much; we learn by doing, and as long as you keep doing, you'll keep learning. Hopefully this post will help you on your way, or "click" in the future

 

[jb783]

thanks guys that's good info. Based on all this I'm using a single coil in my plum veil, vaping at 25 watt, twisted 28 gauge, at 1.1 ohms. It's incredible. Instant heat, great flavor and a lot of vapor.

Dang, it's cloudy in my office right now, lol

 

[Wolfenstark]

My lemo build twisted at 1.4Ω is taking longer to heat than a single 1.4Ω does. So Im using higher watts on this build.
Thats single coil with two wires twisted compared to single build with one wire.

 

[jb783]

My lemo build twisted at 1.4Ω is taking longer to heat than a single 1.4Ω does. So Im using higher watts on this build.
Thats single coil with two wires twisted compared to single build with one wire.

what watts you running at? I had a single twisted 28 gauge at 1.2 ohm and found 25 watts to be about the sweet spot.

 

[Bunnykiller]

not necessarily. Lower resistance with the same gauge wire will heat up faster. Thicker wire takes longer to heat up though, more wire mass takes longer to heat.

looks like yall both said the same thing.....

 

[Bunnykiller]

Exactly. Having less resistance on a larger coil will allow the electricity to pass through freely, taking it longer to heat up. It is the resistance that causes the heat.

its the flow of current/electrons that heat the wire... the less the resistance the more flow the more heat....increase the resistance, less flow occurs less heat is created

considering the same voltage is applied...and the same dia of wire is used

 

[mcclintock]

If everything's the same except doubling up wire and coils, should be the same and therefore sounds like the battery can't drive it. If you're winding twisted coils to have the same resistance as a single wire, you're making them twice as long and that's why it only gets about 1/4 as hot (1/2 the power and twice the surface area).

Given a certain battery voltage, lower resistance draws more power and therefore can make more vapor.... but once you choose a wire size and configuration, then the calculation moves into making that coil work properly.