Right Ohms For an RTA on a Itaste MVP V2.0?

[FreeTimeNow]

So I bought the new Billow rta EHPRO just came out with. It has dual coil ability. Problem is, I don't know how to determine how to build the coils. If I target 1.5 ohms then I have to do a ridiculous amount of wraps using a .26 Kanthal, like 27 per coil.
How can I determine the safe resistance to build for this box, or any for that matter? It can go up to 11 watts.
I did a 12 wrap .26 Kanthal single coil, and it took forever to glow.

 

[State O' Flux]

The wire you use, in combination with the desired resistance and the maximum wattage output of a MVP2... are not balanced. 26 gauge wire is simply too thick for an APV with 11 watt/1.2Ω limits. You need to use thinner wire, or get a APV with a higher output... around 80 watts or more if you want to run 26 gauge, 1.5Ω dual parallel coils.

Obviously, the least costly option is thinner wire... as the only thing that determines resistance is the length and thickness of the wire, from point to point. For dual parallel coils above the MVP2s minimum resistance of 1.2Ω... 32 gauge wire is optimal (31 or 33 is OK to) to obtain a median coil temperature. If you want to run a single coil, 28 gauge would be fine, again... at 11 watts.

How do I arrive at these values? Visit the Steam Engine site (Hyperlink below in sigline), go to "coil wrapping", then scroll to the bottom of the page and click on "How it works" in the left hand corner. Read everything beneath that... in particular the information on "Heat Flux" and "Heat Capacity".

I'll give you an example to verify. For a 1.2Ω desired, single coil resistance, we use 28 gauge wire 67mm in length. Wrapped on a 2mm mandrel, we end up with a 8/7 wrap count with 3mm legs.
With the Heat Flux value set at 11 watts, the "color code" is in the green zone at 163 mW/mm². Want to increase the temperature and decrease the lag time with no other changes? Decrease the wire thickness.

Cheers...

 

[FreeTimeNow]

The wire you use, in combination with the desired resistance and the maximum wattage output of a MVP2... are not balanced. 26 gauge wire is simply too thick for an APV with 11 watt/1.2Ω limits. You need to use thinner wire, or get a APV with a higher output... around 80 watts or more if you want to run 26 gauge, 1.5Ω dual parallel coils.

Obviously, the least costly option is thinner wire... as the only thing that determines resistance is the length and thickness of the wire, from point to point. For dual parallel coils above the MVP2s minimum resistance of 1.2Ω... 32 gauge wire is optimal (31 or 33 is OK to) to obtain a median coil temperature. If you want to run a single coil, 28 gauge would be fine, again... at 11 watts.

How do I arrive at these values? Visit the Steam Engine site (Hyperlink below in sigline), go to "coil wrapping", then scroll to the bottom of the page and click on "How it works" in the left hand corner. Read everything beneath that... in particular the information on "Heat Flux" and "Heat Capacity".

I'll give you an example to verify. For a 1.2Ω desired, single coil resistance, we use 28 gauge wire 67mm in length. Wrapped on a 2mm mandrel, we end up with a 8/7 wrap count with 3mm legs.
With the Heat Flux value set at 11 watts, the "color code" is in the green zone at 163 mW/mm². Want to increase the temperature and decrease the lag time with no other changes? Decrease the wire thickness.

Cheers...

Thank you very much for taking the time for one of the most easily understood ohms/watts explanation. I did find the steam engine after doing my post, and more posts explaining the watts/ohms stuff.
Then just as I thought I was getting a handle on the ohms calculator tool I read a tech sheet on a boxmod and saw it listed an input Volts and output volts so of course now I wonder which value to plug into the calculator. I thought you just used the 3.7 volts of the battery.

 

[State O' Flux]

Thank you very much for taking the time for one of the most easily understood ohms/watts explanation. I did find the steam engine after doing my post, and more posts explaining the watts/ohms stuff.
Then just as I thought I was getting a handle on the ohms calculator tool I read a tech sheet on a boxmod and saw it listed an input Volts and output volts so of course now I wonder which value to plug into the calculator. I thought you just used the 3.7 volts of the battery.

No problem FTN...

With Ohm's law, if you have any two values, you can calculate the other two... but we must remember that Ohm's law doesn't know the limitations of your regulated APV... and will produce all formula values, with no consideration for the hard limits of your device.

With the values of 1.2Ω and 11 watts - the minimum resistance and maximum wattage output values for an MVP2 - we, not too surprisingly, obtain the true maximum current output for the MVP2 of 3 amps.
The last value, amperage, is the regulated current output limit for the MVP2... and why going below 1.2Ω, when you can't maintain true resistance/current parity, becomes... just numbers on a screen.

You will note that, with the above values, 'only' 3.63v is our voltage value... and yet, the MVP2 displays higher than that if we use the voltage setting.
Yes, it will display a higher number, but if you insert the 1.2Ω value and a higher voltage than 3.6v, you've exceed the known 3 amp limit of maximum current output, and that displayed voltage is, again... just a number on a screen. ;-)

If, for some reason, you want your MVP2 to display 'true' volt and watt values, you need a resistance of 2.3Ω... which when you think about it, is right around the value the MVP2 was originally designed for... before low and sub-ohm resistance came into vogue.