Curious about Atty voltages

[oldsoldier]

I have been reading tons of threads on the pros and cons of 5V and 6 V vaping. I've even heard people talking about 7.4V...

So here is a quick question. Why not 12V? 12V @ .5A is only 6 watts at the atty and I've heard lots of folks consider 6-8W the sweet spot form most juices.

The reason behind the curiosity is I've got tons of wall warts of various capacities that are sad orphans and therefor candidates for PTs or big fat desk mounted pipe mods. Would the high ohms of these units (24) be a reason they wouldn't be suitable? Or is it more of a matter that "it ain't done that way"?

 

[tdh]

There are several reasons.

1. Size: 12v@0.5A is 24 ohms. That would take about 7 inches of 38ga nichrome wire or 10.7 " of 36ga. It would be hard to fit that much into a standard size atty.

2. Thermal mass: Temperature is just as important as power, and more resistance means more wire which takes longer to reach critical temp at a given power level. In the case of 12V, about 4 times as long to heat up. This will also heat up the body/tube of the atty way more than another configuration with the same wattage. Maximum temperature is a [basically] function of current squared.

3. Convenience: It is cheaper to make compact units at lower voltages than at higher voltages. Way more so than with wall adapters. A 12V battery powered device would either require a fancy regulator (some of the regulators used in vv mods could handle 12V just as easily as 5v) or a lot of batteries.
3.7V is common because that is a single cell.
5v is common because there are a lot of 5v fixed output regulators
6v is common because stacking a pair of 3v batteries doesn't really require any regulation
7.4v is common because people are escalating and getting lazy (2 lion cells with no regulation)

That said, there is no reason that you can't make higher voltage devices. I have an 8.4v 20w watter cooled vaporizer that works fine (I got drunk one night and felt like building something). In general, you don't want to go much below 1A. I usually stay in the 1.5-2.5 amp range. Low currents usually work better with low air flow, but you need more amps for a high-flow device.

 

[oldsoldier]

Thanks tdh.
I had sort of figured that the high resistance was one of the main reasons but your explanation of the thermal mass issue seals the deal. It was more of a curiosity thing than anything else- I've learned a lot from the folks here on ECF. I just need to make sure that the facts I get here don't push other facts out of my brain ala Kelly Bundy. It might get embarrassing to forget my name or address because something like thermal mass or the requires length of a 38 ga nichrome wire to handle 24 ohms pushed them out of my head