Hi Dartington,
Protank 3 are dual
coils and not really a good vape on an ego type battery. Understand, a 2ohm dual coil means you have two 4ohm coils wired in parallel, with each coil acting as a single 4ohm coil . In other words, the heat per coil is halved.
So, you really need to vape at at least 6 volts setting on your battery, or more to get a decent performance from a dual coil. Probably more like 8+ volts battery setting.
I would stick with single coils for your type of battery.
You can use the chart, if using dual coils then double it, i.e. 4ohm at 3.7volts you will see you are barely getting enough vapor...(vaping at 3.42 watts)....it's very cool ......even at 4.2volts dialed in on your battery, you will barely be vaping at 4.41 watts.
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Whereas, using a single coil @ 2ohms, with your battery dialed in at 4.0volts, you'll be vaping at a nice warm 8 watts.
The 2 ohms should be okay at 4.2 volts
Yes, on a single coil, a 2ohm coil would vape fine at 4.2volts. That would be 8+ watts, a nice warm vape.
On a 2ohm dual coil, that is not the case. Hope the above makes sense.