amp limit on kanthal 30g?

[Jolly Boots Of Doom]

so I am building my first battery mod and it is going to be a high voltage mod, putting out 6v. I want to know how low I can drop the ohms, before this becomes dangerous. I already did the math on a few common coils, 2.2ohm gives me around 16.36w and 2.7amps. but if I do a 1.8ohm I get 3.33amp with 20w. I was hoping for something around the 1.8 but I figure with a high voltage mod, this is the equivalent of sub ohm at .68ish with a 3.7. Am I right? Or is there an amperage limit on the kanthal that I am overlooking? I am trying to avoid going

 

[LucentShadow]

Hi. You're pretty much correct on the current and wattage numbers, other than a freshly-charged lithium battery would run more like 4.2v at about 26 watts, with .68 ohms. Average would be about 20 watts, as it discharges, though.

As far as coil amp limits go, I don't know that anyone actually looks into that much, with vaping. If you dig into the specs on the wire, you could probably come up with the amperage required to hit the melting temperature of the wire. This is probably quite possible on a dry burn with almost any lower-resistance setup, though.

In practical use, as long as you feed enough liquid to the coil, the boiling of the liquid will limit the temperature of the wire to near the liquid's boiling point, which is much lower than the wire's melting point. You need to design your wicking solution to keep up with your coil's heat. This is usually something that you need to experiment with yourself, since you can't usually replicate someone else's build exactly.

The major concern with limiting amperage would be to prevent overloading the battery cells or device circuitry. The datasheets for the particular cells or circuits need to be consulted to find their limits. This is not always easy, but should be done. If you were using IMR lithium cells with a dc-dc converter to get the 6 volts, you'd need to make sure to stay within the safe limits of the converter and the cells.

Looking at a different thread, I suspect that you are looking at 1.5v alkaline D cells, four in series. I can't recommend that, if so, as my research indicates that they are designed for a max of 1 amp draw, usually. They are generally designed for long life in low-current applications. As I recall, Maglite bulbs are only around 6 watts. Check this thread, for some more info:

Maximum current draw for D alkaline's

If you want that form factor, you would be better off looking into NiMH cells. They are not common in D size, and some of those are just AA in larger shells. However, they can be found:

Tenergy Premium NiMH D 10000mAh Rechargeable Battery

NiMH is much more suitable for high-drain applications. From the link above, you can see that, though I would not fully trust that max rating. Those top off at 1.25v, unloaded, though they run more like 1.2, so 4 of them would be about 4.8v, while 5 would be about 6v.

To conclude, I would not worry so much about popping a coil, when popping a battery cell is in question. Check your battery limitations, and stay within those.

 

[MorpheusPA]

Most of the time, wire amp limits are given in free air circulation conditions and have to be downrated if used in an enclosure.

In our case, with liquid-cooled wire (except for a dry hit), the wire can actually be up-rated. Only the legs of the atty aren't directly cooled, and thermal conductivity is good enough to cool that decently by funneling the heat into the cooled coil, for short distances, at least.

Over 20 watts the probability of popping a coil starts to grow, and 30 gauge Kanthal will pop more easily than larger wire. Even if so, it becomes a learning experience and nothing more as popped coils generally do no harm to the user. We should note that (although I tend to be much lower wattage when vaping) I've never popped 32 gauge and that's considerably thinner than 30.

+1 LucentShadow above regarding batteries. I'd avoid alkalines. In addition to what he/she said, they also get leaky when overstressed or fully drained. Nobody likes cleaning battery acid out of their vape. Go with NiMH if you wish to use a 1.2-1.5 V cell.