Thanks a lot really appreciatedCapacity of the battery is referring to the mah hours. I think what you are referring to is the CDR or constant amp discharge rating.
In a regulated mod your coils resistance doesn't have anything to do with current draw. You set the power you want, the chip sees the voltage present from the batteries and then draws the amount of current it needs from the batteries to reach the power level you dial up. The chip then steps up or down the voltage and does the inverse to the current to supply the power to the coil.
*DNA200 chips are buck only meaning they only step down the voltage and step up the current*
The VT 133 is a dual series mod so fully changed the chip has 8.4V applied. Fully discharged ~6v. To see the current draw, take the wattage (power) you dial up and / it by the voltage. (25w/6v = 4.2amps) Most of the batteries we use have a 20 amp CDR rating so that would be well under that. As the cells discharge, the voltage drops, the current draw goes up.
As the mah (capacity) of the cell increases the CDR (amp rating) decreases. It's a balancing act. You want to select a cell with a high enough CDR but one that also has a decent amount of capacity. I think 20 amp CDR cells are a good balance between CDR and capacity..
Short answer is a 20 amp cell is good for ~120 watts in a dual battery DNA. It's good for about 180 watts in a triple battery DNA (throughout the run/worst case scenario when the batteries are fully discharged).
Here's a link to a very good article on the best batteries for vaping written by Mooch:
http://vaping360.com/top-5-18650-batteries-for-vaping/
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