God damn! I thank you very much for such a well detailed reply! I've looked up on battery safety and i have a app in my phone (That is pretty much the same as steam engine) which is called ''Vape Tool'' on my android phone. It's a great app, btw. Allows you to save builds and you can choose between normal, parallel, claptons, etc and if it's a singe, dual, and all the way up to six, i think. It's a very detailed app. But anyways... i bought 3 VTC4's which are rated 20AMP by Sony and 23AMP by mooch. I will be building around .2 ohms and the app actually shows the AMPS that will be drawn out of the battery. And as for ''When using ohms law to calculate your amp draw use the max battery voltage of 4.2 volts to make your calculations.'' The app does allow me to change the voltage, but it's labelled as ''Change base voltage''. Do i choose 4.2? Doesn't the voltage quickly drop from 4.2 to 3.8-3.7 ish after a few hits? And i used the ''Bettery drain'' thing on steam engine and it says on a .2 ohm build i would have 9 percent headroom, while the recommended would be 20 percent. Is that unsafe...or?