MrBogdi

Yeah, i studied all about ohms law. I have samsung 25R and sony vtc5, both doing poor in this situation

Thats what I was taught to do with married batts The mod recognizes each batt I guess

Oh, ok Thanks mate

18650 Batteries can charge up to 4.2V and produce that when first put into a mod.  They will spend most of their life around 3.6V as that is the "nominal" voltage.  Obviously 4.2V will pull more current.  It's all about safety with a mech mod.  There are no electronics protecting the mod.  

We'll need to know a little more about your setup to give you an accurate answer, but In a mech mod, the lowest resistance load you can safely go with on a fully charged battery (4.2v) and stay under your battery's 20 amp limit is .21Ω, which will yield 84 watts.
Voltage / Resistance = Current (amps)..........Voltage² / Resistance = Power (watts)
Remember, your resistance can/will change do to a variety of reasons, so it's imperative that you keep a close eye on your coil's resistance fluctuations, especially if you are setting it up to run at your battery's safety threshold.