The Tarot mod looks quite nice. Gotta wonder how they're pulling 200W off just 2x18650's tho
Our single 18650 tube Mods use a Buck/Boost DC-DC Converter, which can both increase and decrease the supplied Voltage from the battery in a 6.0-3.x Volt range, but most Series stacks only use Buck, which means they cannot output a Voltage above the batteries' Charge level. But...
Looking at 30A being the safest Continuous Amp draw to consider, Watts = Volts x Amps, so V = W/A.
200W
Max/30A
Max = 6.667V
Now, V²/W
Max = Ω, so (6.667V)²/200W = 0.2222Ω
Max
So 200W could be reached with 6.667V by using a 0.22Ω coil setup or less, and 6.667V is easily attainable from a Dual Series Stack 18650 in a Buck system. Each battery could be discharged down to 3.33V.
Many Mods today cannot supply their upper Watts Spec across a broad range of Ohms, so this
could be how they are doing it.
And at 8.4V (both batteries fully charged), 200W could be reached briefly with 0.35Ω, drawing only 23.8A.
NOTE:
None of these calculations take a Buck DC-DC Converter's Max Voltage out into account, nor the chip's efficiency, nor Battery Lag. There is normally a decrease in a Buck Converter's Max V
Out that is below the supplied V
In by about 1.0V. So the calculations above may be exaggerated a bit by using Max figures, but they are only given as examples.