Guide to Ohms Law and Safe Vaping

Guide to Ohms Law and Safe Vaping

Vaping is a fantastic way to cut down and even stop smoking, but with the ever-changing market, it can sometimes become a complex beast. Further to some of my other articles, today I will be covering ohms law and safe vaping.

As with all electronics, you have some golden rules to adhere to when you decide to move into the DIY side of things. By sticking to these rules you have ensured a safe experience and an understanding of not only the end result but how you achieved it.

We have all seen the different devices that boast so many watts, and will fire so many ohms, but what does this all mean? When I first started vaping, I made a phone call to a local vape shop to see if they had the coils I needed in stock. They asked me “what resistance would you like”?

Ohms Law and Safe Vaping 

What are ohms law? What is resistance?

Back then I had no idea that there were different resistance coils, and I had absolutely no experience in ohms law. This forced me to look into the difference between a 1.8ohm coil and a 1.2-ohm coil and so my journey into power began!

I think of ohms as a very simple analogy. Imagine there is a door, with a person standing on one side of the door. The door will not move without any force put onto it (this is your voltage) and the door itself has a weight (this weight is your resistance).

Imagine you are trying to push the door at a constant force and it doesn’t move, you need to either apply more force to the door (volts) or reduce the resistance of the door (ohms).

By putting too much power into the door and the resistance is low, that door is going to swing open quickly and you will fall through it. When the resistance is too high for the amount you are pushing, the door won’t move. This is a basic analogy of resistance.

So let’s take a mechanical mod. This has a fixed voltage (on a fully charged single 18650) of 4.2V, so if the coil resistance is too high, you cannot add more power. So what do you do? That’s right, lower the resistance.

What about safety?

Guide to Ohms Law and Safe VapingThe biggest thing to look at when buying batteries and building your own coils is the amp rating. This is very important as it dictates if the build is safe or not.

Having too high of a resistance will not be dangerous, but will deliver a poor vape. However, having too high of an amp draw on a battery can be very dangerous! I go into this in a lot more detail in another blog post I have done that can be found here.

So how do we work out ohms law? When buying a regulated mod you do not need to worry about this. They have built-in circuitry that will tell you if the build is unsafe and they will not fire, however when using a mechanical mod you do not get the same luxury!


The easiest way to work out the amp draw on a battery is as follows. Amps drawn = Voltage / Resistance. So if you have a fully charged 18650 at 4.2 volts, and your resistance is 0.5 ohms you would do the following. 4.2/0.5 = 8.4

The above would have a draw of 8.4amps. So if your battery has a maximum draw of 20amps, you are well within the range of safety.

If you have a resistance of 0.15 ohms though, the end result is very different. 4.2/0.15 = 28amps. If your battery is rated at 20amps, then you are pushing the battery too hard and this can cause it to become unstable.

This will not only damage the battery, but there is a strong chance it can go into something called “thermal runaway” and result in an explosion. This is no joke and has happened to uneducated people in the past. We have all seen the “vaping is not safe” articles about batteries blowing up!

How do I pick a safe battery?

If you are educated and do not operate outside of the intended values, you will be absolutely fine. This is applicable to all batteries and electronics and not just vaping.

The best thing you can do is to buy batteries that have been tried and tested by the professionals and operate well within the realms of their ratings. The difference between a well built 0.25-ohm coil and a 0.15-ohm coil is minuscule to your vaping experience, but in terms of the safety, it’s huge! (4.2/0/25 = 16.8 amps is within the 20am rating!)

The best 18650 batteries on the market for safety are the Sony VTC6, the Samsung 25R and the LG HE4.

The best 20700 batteries on the market for safety are the iJoy 20700 or the Ampking Ak3030.

There are many other batteries on the market that others may like more, so feel free to add any that I have missed the comments. One thing to remember is to ALWAYS look at the constant rating and not focus on the pulse rating.

I suggest typing the battery model, the “mooch” into google, as he compiles thorough reports of real results as the manufacturers very often wildly exaggerate their batteries (which is incredibly dangerous!)

Mike Strong

I have been vaping for over 5 years and have been a keen hobbyist ever since starting. I moved into the review side of things after the success of my @mikethevaper Twitter page and have been striving to provide help and knowledge ever since.