DNA40 TC and Battery Safety

[Caterpiller]

Thinking about doing my first TC Nickel build.

Quick safety question.

If I do 28g, 12wraps, 2.5mm ID, Nickel, it will likely come out around 0.16ohms.

Is this not a concern in terms of battery safety?

Using VF DNA40 - Derringer rda

batteries: 2x LG HE4 18650

I believe these batteries are 2500mah, 20A Continuous, 35A Peak.

 

[Oberon75]

It looks like you will be fine. Keep on mind that you aren't actually vaping at .16 ohms. As you heat the coil, the resistance increases significantly which is how temperature is controlled.

Sent from my HTC One M8 Harman/Kardon edition

 

[Cullin Kin]

Even at 0.16Ω and 40W... You're only pulling 15.81A ( I=√(P/R) ). This is the beauty of regulated mods, you can build low and be safe... To a point. That all goes out the window when you start turning the wattage way up though.

I don't know if the DNA40 works the same way, but the Snow Wolf I just got varies the wattage as you are inhaling in TC mode. When it starts getting too hot, the TC kicks in and turns down the wattage until it's cool enough to increase the wattage again. So really, if you had it set at 40W, you're not remaining at 40W the entire hit... You're actually under 40W most of the time. Again, I don't know if the DNA40 works the same way... Point is: You're safe.

ETA: Also, as Oberon said, your resistance does increase when the nickel wire is heated. Thus the basis of temp control... The coefficient of resistance, or how a metal wire's resistance changes with changes in temperature.

 

[bwh79]

If I do 28g, 12wraps, 2.5mm ID, Nickel, it will likely come out around 0.16ohms.

Is this not a concern in terms of battery safety?

In a regulated mod, the amp draw is only determined by the wattage setting (and battery charge), and not by the attached resistor. This is because the battery only ever outputs a single voltage, equal to whatever it's charge level happens to be at the time. So if you're set for 60 watts and the battery is charged to 4 volts you are pulling 60/4=15 amps, regardless of whether you are dumping those 60 watts into 0.16 ohms, or 16.

Unlike a mech mod where you do all your safety calculations assuming a full charge of 4.2v, the amp draw is actually higher when the battery is drained, rather than when it is fully charged. If you're pushing those same 60 watts with a drained battery at 2.7 volts, for example, the amp draw is a bit higher at 60/2.7=22.22 amps.

 

[Ryedan]

A 20 amp battery is just fine at 40 watts in a VW mod. Atty resistance makes no difference. The mod limits battery amp draw to what it takes to make 40 watts which is 15 amps max at 3 volts.

Here is the Steam Engine battery drain calculator. Fill in the blanks and you'll see what how it works. Minimum battery voltage (I use 3V for a one battery mod, 6V for two batteries in series) draws the most amps as opposed to 4.2V in a single battery mechanical mod.

 

[Caterpiller]

Thank you all, that clears that up.

So on the setup mentioned above is there a lower limit on the safe ohms level of a nickel build, or can you build as low as you like?

I'd assume the DNA40 has a cut off ohms level that it won't fire below, but I don't know what that is.

 

[Cullin Kin]

Thank you all, that clears that up.

So on the setup mentioned above is there a lower limit on the safe ohms level of a nickel build, or can you build as low as you like?

I'd assume the DNA40 has a cut off ohms level that it won't fire below, but I don't know what that is.

I think the cut-off for the DNA is 0.1Ω for 'temperature sensing wire,' but I could be mistaken. They may have lowered it. I've seen 'sweet-spots' all the way from 0.075Ω-0.4Ω....