Fattlestar or Bassnorma,
Let's see if I got this right. I could get a mech put my 18650 2500mAH 3.7 battery in it, attach my Delta II .5 ohm to it and according to the ohm calculator lets say fresh off the charger I pull 4.2 v straight from battery I would be pushing 35 watts through the Delta II which is well within its range. So I would be good right? Then when I notice performance drop off charge batteries. Do I understand how that works?
That all seems correct to me, you've got it right. Switch out batteries as soon as you feel the vape drop off and you're golden. I usually switch batteries ~3.7v or 3.8v, as that's where my builds start to sag.