Wattage range w/ sub-ohm coil build question.

[King_A]

Hey guys,

So I'm about to build my first coils ever in a Tsunami 24 RDA using my SMOK Alien 220W box mod. I'll be using NiChrome 80 24 gauge wire. Dual coil build. I have spent the better part of the last 2 weeks reading online, watching tutorials and such. I am confident that I will succeed. I have all the tools I will need. Still, though, there are a couple things that puzzle me. One of them being the range (wattage) at which I can ''safely'' vape my coils. For instance, NiChrome 80 24 gauge wire, dual coil (tightly wrapped) build which I am aiming at an .3 ohm resistance for. Now, according to steam-engine, I need to do 9 wraps (rounded up) around my 3mm bit with about 4mm leg length to reach that target resistance.



What I don't fully understand is the ''Heat flux'' section. Like I said earlier, I will be using an Alien 220W box mod. Now, from what I understand, this box mod uses the batteries in series. Same amp limit but double the voltage. I will be using a pair of LG HG2 rated as a safe 20AMP battery by Mr. Mooch. I understand that the batteries can be pulsed at a higher AMP usage but I'm not planning on doing that. I usually vape around 50-80W which is why I chose a .3 ohm resistance. I like my vape warm (not hot) and full of flavor. I'll take flavor over clouds. What I am trying to understand is what is the ''safe'' range at which I can vape those coils without burning them out, if that's even possible with ''regular'' vaping... The ''Heat flux'' section, as I understand it, is just an average estimation. Correct? I was not able to find a chart or any infos regarding this matter online or maybe I am not looking for the right thing...

So my questions are :

- What is the ''safe'' wattage range I can vape my coils at?
- Is burning your coils/wick, because of using too high wattage, even possible if the wick is fully saturated with juice?
- Does the different type or wire affect the safe wattage range of the coils or just the resistance?

Also, if someone could help me understand the ''heat flux'' section a little better, that'd be awesome!

Thanks for the help guys!

 

[bmclaurin]

Heat flux is just a measure of how the power is distributed across the surface area of the coil. In other words, for a given power setting on your mod, how many milliwatts of that power is being output by each square millimeter of surface area of the coil. All other things being equal, the larger the surface area, the lower the heat flux (because the power is being dissipated across a larger surface). It's supposed to give you a rough idea of how "hot" the coil will be at a given wattage. But frankly, I wouldn't get too caught up in that. After you've built a few coils, you'll get a feel for how hot the coil will be at given wattages.

For determining the best wattage for a given coil, well that's completely up to you. My advice would be to start low and keep bumping it up a bit until it feels "right" to you. That's all there is to it.

In terms of safe wattage limits for variable wattage devices, it generally depends on: the constant discharge rating (CDR) of your battery, the efficiency (EFF) of the voltage converter in your mod, and the low voltage cutoff (LVC) of your mod. Here is a simple formula that will tell you the maximum wattage your cells can safely deliver on a typical variable wattage device:

LVC (in volts) x CDR (in amps) x EFF%

So with a 2x18650 VW series mod (like the Alien), let's assume it has a low voltage cutoff of 3.0 volts per cell (6.0 volts total), and has 90% efficiency. Using quality OEM 20A cells like your HG2's, you would have:

6.0v x 20.0a x 90% = 108 watts

I used the mod's LVC for conservatism. In reality, your cells will be able to safely deliver more wattage when they are not near depleted.

Notice that the coil material or resistance has nothing to do with it. That's because you are using a regulated device in which the battery does not directly interface with the load; the chip does that instead.

EDIT: *WARNING FOR NOOBS* The above formula is for REGULATED DEVICES only!! Unregulated devices work completely differently.

 

[King_A]

Heat flux is just a measure of how the power is distributed across the surface area of the coil. In other words, for a given power setting on your mod, how many milliwatts of that power is being output by each square millimeter of surface area of the coil. All other things being equal, the larger the surface area, the lower the heat flux (because the power is being dissipated across a larger surface). It's supposed to give you a rough idea of how "hot" the coil will be at a given wattage. But frankly, I wouldn't get too caught up in that. After you've built a few coils, you'll get a feel for how hot the coil will be at given wattages.

For determining the best wattage for a given coil, well that's completely up to you. My advice would be to start low and keep bumping it up a bit until it feels "right" to you. That's all there is to it.

In terms of safe wattage limits for variable wattage devices, it generally depends on: the constant discharge rating (CDR) of your battery, the efficiency (EFF) of the voltage converter in your mod, and the low voltage cutoff (LVC) of your mod. Here is a simple formula that will tell you the maximum wattage your cells can safely deliver on a typical variable wattage device:

LVC (in volts) x CDR (in amps) x EFF%

So with a 2x18650 VW series mod (like the Alien), let's assume it has a low voltage cutoff of 3.0 volts per cell (6.0 volts total), and has 90% efficiency. Using quality OEM 20A cells like your HG2's, you would have:

6.0v x 20.0a x 90% = 108 watts

I used the mod's LVC for conservatism. In reality, your cells will be able to safely deliver more wattage when they are not near depleted.

Notice that the coil material or resistance has nothing to do with it. That's because you are using a regulated device in which the battery does not directly interface with the load; the chip does that instead.

EDIT: *WARNING FOR NOOBS* The above formula is for REGULATED DEVICES only!! Unregulated devices work completely differently.

Thank you very much for all the info! Very informative and well put! Much appreciated!

Apparently, the Alien can take down the batteries all the way to 2,8v. Personally, I change the batteries when the battery indicator shows they are at 25% left. And I found online that the efficiency of the Alien is quite high. Probably not as good as the DNA 250 chipset but I assume the 90% efficiency is correct. So 5.6v x 20.0a x 90% = 100,8 watts. But like you said, with fully charged or say, nominal voltage of the batteries, I can vape at 129,6 watts safely if I switch out the batteries before they are too empty. But all of this is irrelevant because I will not vape at 130 watts LOL

Again, thank you very much for your reply!

 

[King_A]

Was aiming for .3 ohm. Oh well, .25 ohm ain't so far, ain't so bad for my first time. Lot harder than I though too Lol

 

[bmclaurin]

Nice!