After having used dual coil cartomizers exclusively in my tanks, I had become somewhat dissatisfied with them with an occassional burnt taste with my e-liquids. I was quite certain that the juice delivery to the heating coils was adequate, so I ruled that out as the reason. I wondered if single coil cartos would be better, and decided it was a good time to try some in my tanks. I did some research into dual coil vs single coil cartomizers on ECF.
What I found were mostly opinions. Many people had switched from duals to singles, arguing that the dual coils didn't produce enough benefits to warrant the additional drain on battery life. There were others that preferred dual coils, of course.
There were statements made that dual coils were developed to be able to provide more vapor production for fixed voltage PVs, via twice the number of coils within the cartomizer. However, there were skeptics to that statement who claimed that for a dual coil to really shine, voltages of 4.5v and higher were required. Contradictory theories? I thought so, too. I was not able to find any scientific evidence to any of the above.
Long story made short, I decided to give single coils a trial. I switched out all of my dozen or so tanks to single coils...same brand, same ohm resistance, same number of holes. The verdict: I was and am impressed with the single coils. Same vapor production and flavor, no more burnt taste, and the expected increase in battery life. Your results may vary from mine.
The following is the amateur scientist expressing myself. Being that dual coils have one coil over another, I theorize that the top coil often is not getting enough juice, unless you happen to top off your dual coils frequently. Look at the below diagram of a cartomizer.
click to enlarge image
The diagram depicts how a punched carto in a tank works, but the principle I want to get across in this discussion is valid here for a cart used alone. Even if you saturate the entire polyfill batting, the juice is going to be pulled downward to where the atomizer is. This is why the top part of the polyfill always looks dry.
The top coil of a dual coil cartomizer going to be located about midway up the cartomizer, so considering my elementary understanding of physics, that top coil is going to often not have enough juice around it to keep it from burning the surrounding wick and polyfill. This probably explains why I experienced frequent burnt taste when using dual coils.
This problem doesn't occur with a single coil, as that heating element will always have the most juice around it.
