I am big on safety when it comes to the dangers of batteries. I have a reuleaux rx 2/3. I have a smok tfv8 tank. They only come with <.3 coils. I have Samsung 25r batteries. Is it safe to vape at 4.45v/90watts? It says I'm pulling 20A on the mod. I had efest 3500 with a continuous rating of 10A and was doing the same. Are either of these batteries safe to vape with this setup? Sorry if I sound like an idiot, but I don't want to start smoking again, but I would also like to keep my face.
For a regulated mod.. don't buy cheap rebranded or factory 2nd batteries and DO buy a high quality battery charger.
If a battery has a "pulse" rating printed on it.. don't buy it
if the wrapper does not say SONY, SAMSUNG, LG.. don't buy it
if the battery does say SONY, SAMSUNG, LG and has a pulse rating.. Don't buy it. (sony,samsung,lg do not put pulse ratings on batteries)
By the way.. the only times I have every heard of a regulated mod going boom was when it was improperly charged. (like they include a usb charger to plug into your computer.. don't plug it into your IPad or telephone charger.. lol)
I actually had the positive ring on the 510 drop across the negative lead, and totally short (hard short) my 100w mod.. but it ddn't blow up. The fuses took the hit. Killed the mod, but it didnt blow my face off.. just a soft pffftttt.. and whisp of smoke. Batteries were still good even.
And may as well mention it now.. check your batteries before you charge them and again before you put them in your mod. Maybe a pigeon flew in an pecked at them while they were charging and tore the wrapper... or maybe you missed a small tear when you put them on to charge.. either way.. checking twice is a good habit to get into.
The thing to remember is don't buy cheap batteries. LG, SONY, SAMSUNG, high drain batteries. You will want 20 to 25 amp continuous draw rating.
Now here is where it gets a bit technical... the lower the continuous draw rating (say 20 vs 25) the higher the MAH rating. SO.. you might have a 3000mah @ 20 amp continuous draw or you can have a 2500mah at 25amp continuous draw. What's the difference? The amount of time you can go between recharges. Does the amp rating make a difference to your regulated mod? Not one bit. Software handles the amps, watts, volts, So safety wise, a 20amp 3000mah is just as good as a 25amp 2500 Mah. The only difference, is the amount of time you can vape between charges. The higher continuous amp rating MIGHT give you a fractionally lower ramp up but at the cost of more frequent battery recharging. Remember.. if you use high quality, brand name batteries, you are fine in your regulated mod.
The main area where you need to really be concerned with the math (amps, volts, resistance, watts), is when you get into mechanical mods. For that, you can and should do your own research, but ask forum members for help, as in what you should be looking for. But that is a whole new ballgame. If you want some examples of mechanical builds and batteries, check out the cloud chasing section. Fair warning... the builds you see there are kind of unbelievable. But we do know our batteries.

we have to! Remember I said, don't buy batteries with a pulse rating? Here is why.. it is useless. It means absolutely nothing. That battery on a mech will pulse at whatever amps I tell it to pulse at according to the resistance of the coil I put on it. It is up to ME to know how many amps the battery can handle and for how long it can handle it.
Now, Im not saying to run out and buy a mechanical mod. I only included the information to demonstrate the difference between regulated and mechanicals. Regulated.. the mod does the math and juggling act. Mechanical.. the user has to know the math and juggle his own knives.