I keep seeing posts on internet forums where people are asking things like “Hey guys! Is this battery safe to use with a 0.00000012ohm coil????”

No. Let me save some time here; * NOTHING* is safe to use with a dead short.

Look, I get the cloud chasing urge. It’s pretty cool to see someone single handedly blot out the sun for a second with juice. But you have to understand that once you cross into subohm territory, you have pretty much thrown safety right out the window.

And it’s really not even necessary. Go talk to Lance over at Steam Monkey and ask him about cloud generation with 2ohm coils. There are safe ways to do it.

But some of you are going to do it anyway.

The single biggest thing that you need to know is whether or not you are over drawing your battery. You * need* to calculate the drain rate for your battery, and you need to do it before firing a coil.

Wanna blow a battery up? Fire it with an atomizer attached to it with a resistance that causes greater amp draw than the battery is rated for.

**Max drain rate in amps is: Capacity (in mAh) x C rating / 1000 = Amps**

You are going to see that again.

Let’s look at one of the more popular mod batteries, the AW IMR 18650.

Now these are generally what I recommend for use in 18650 mods, but they come in two variants; 2000mAh and 1600mAh, and the difference between them is important.

First we’ll take a look at the 1600mAh:

Specifications (this is from a vendor website):

Nominal Voltage : 3.7V

Capacity : 1600mAh

Lowest Discharge Voltage : 2.50V

Standard Charge : CC/CV ( max. charging rate 4.5A )

Cycle Life : > 500 cycles

Max. continuous discharge rate : 15C

So what is the maximum discharge rate for this battery? 15C doesn’t really tell you anything unless you know what it means. C rating is nothing more than the capacity of the battery. This particular battery is a 1600mAh capacity, so it can ostensibly safely sustain a draw that is 15 times its capacity, or 24 amps.

So what does that mean if you’re playing with sub ohm coils? It means that with a fully charged battery you can probably vape anything down to about 0.3ohms (at about 88w) and not over draw the battery (at least for a couple of seconds, the charge isn’t going to last long at all with that kind of draw on it).

Now let’s look at the 2000mAh:

Specifications (again from a vendor website):

Nominal Voltage : 3.7V

Capacity : 2000mAh

Lowest Discharge Voltage : 2.50V

Standard Charge : CC/CV ( max. charging rate 2A )

Cycle Life : > 500 cycles

Max. continuous discharge rate : 10A**As a side note, I believe that is incorrect. I’m pretty sure this battery actually has a 10C rating, and someone read that wrong and typed it as 10A, but I’d have to do some research to confirm that, so we’ll take the vendor at their word for now.

Hmm, this one is listed in amps rather than a C rating. In case you are wondering, for a 2000mAh battery a 10A CDR (Continuous Discharge Rate) is a 5C rating. Despite this battery having a higher capacity, if you vape anything less than 0.5ohm on it, you’re going to be overdrawing the battery, and you’re gonna have a bad time (this particular battery is LiMN, so it probably won’t blow your face off, but you’ll lose the mod at minimum).

How do I know that?

An AW IMR Li-Mn 18650 battery has a capacity of 1600mAh (let’s use that variant for this example).

The C rating is 15C (it can supply 15 times the capacity).

Therefore the max discharge current in amps is: **1600 x 15 / 1000** (1600 multiplied by 15, divided by 1000) = 24 amps (told you that you’d see that again).

So you can see that with this particular battery, you have to get pretty dang close to a dead short to have a problem, but what if you didn’t know any different, and threw the 2000mAh version in the same mod that had a 0.3ohm atomizer on it? You’re now drawing 14A through a battery that is only rated to give you 10A. That can lead to catastrophic battery failure.

Now LiMN batteries generally fail by venting hot gas, so you might burn your hand (and you’ll probably lose your mod), but what if that were an ICR battery? Those tend to vent flames and explode.

It may not happen the first time you do it, or the 10th, or even the 100th, but it might happen the second time. Or the ninth. If you don’t do the math, you are taking an unknown risk. It’s like playing Russian Roulette with a gun that someone else loaded out of your sight.

This is even more true if you don’t have the C rating for the battery you are using, like the crappy blue ICRs that come with most “kits”. This is a big part of why I recommend that you toss the generic batteries that come in those kits, and buy some good batteries, something that you actually have all the relevant information for.

You need to pay particular attention here if you’re running a sub ohm coil on a mech and didn’t know any of that, or don’t know what the max discharge rate for your battery is (again; toss the generic blue ICRs that come in most kits, know what your equipment is rated for).

Vaping is awesome, but let’s not give the people who don’t know anything about it a reason to push for banning it eh?

Try using ohms law. V=I×R where V is the Voltage in Volts I is the current in Amps R is the restance in ohms. V devided by I gives you the resistance, R=V/I, I=V/R. Ive read twice now two people calling the current amperage when its actually Ampage and to find this you should devide the Voltage by the resistance in ohms. I hope this helps.

Using Ohm’s Law for what? Calculating the actual draw? I don’t understand what you’re referencing.

Amperage is correct. The unit of measure is an Ampere (commonly shortened to amp).