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Ohm’s Law – A Beginner’s Guide For RDA/RBA Enthusiasts

I have been doing a lot of research over the past few months, mainly about ohm’s law, and other electrical properties. I’d like to say this was for some grand project, or a time machine, but, alas, it is not. No, this little endeavor of mine is ALL about vaping. And the reason as to why I’ve been looking into all this good stuff is simple: every vaper NEEDS to know about Ohm’s Law.

All to often I see novice vapers jumping into building on RBA’s and such but not really having any knowledge of why ohm’s law is so important — or, for that matter, what ohm’s law even is! This is something I’ve been thinking about for awhile, but this week I decided to FINALLY put pen to paper and write this sucker up.

I dug deep, did hours of research and grew a few more brain cells in the process. And now, dear reader, I am ready to relay onto you what I found out about RDA/RBA building and Ohms Law.

Right. Here goes.

Ohm’s law consists of 3 main electrical properties, which are:

V = Voltage
I = Current
R = Resistance

Voltage is simply defined as the difference in electrical potential. So if you have a 9V battery the difference between the positive and negative posts would be 9V difference. Voltage is measured in Voltages.

Current is the rate at which electrons flow. Current is measured in Amperes 1 Ampere = 1000 Milliamperes.

Meanwhile, resistance is an object’s opposition to the flow of electricity. Imagine a car that has broken down on a 2 lane road, the broken down car is causing traffic to slow down much like resistance does, the more cars that are broken down the slower traffic will go, meaning that the higher the resistance is the slower the electricity will flow.

From Ohm’s triangle knowing what VIR is we know that

I= V/R
R= V/I

Now — I know what you’re thinking: how the hell is vaping related to all of this? Well, we have the V.I.R. But what about the P (Power). That’s where the Wattage comes in. This is where things are going to get tricky so try to stick with me on this, if you will.

First off we will find wattage with this formula.

Wattage = V²/R

Why is wattage or P important?

Simple: the more P you have the more heat you will produce and thus in turn the more vapor and sometimes flavour you will get. Knowing how division works, we all know that the lower your resistance the higher your wattage will be.

This is why vapers like to know the Voltage of their battery. The lower the volts go the lower the wattage will be. And this is where things get dangerous — too high on the wattage and you could short out a battery or pop a coil in one simple push of a button.


Too low and… you get nothing. All batteries are made to handle specific loads. That is why sub ohm vaping is so hard or dangerous. But arming yourself with the proper knowledge and batteries you can greatly lower this risk. Although you will NEVER, 100% eliminate the risk.

That’s just a fact of life with electrical goods.

Different Batteries, Different Mods

The right type of batteries will depend on what you want to do. If you are not interested in sub ohm then your choices are broader and the risk associated with what you’re doing lower. Staying within 1.1-1.3 ohms you are pretty much always going to be in the general safety area. I say general safety because safety is never guaranteed when working with electricity.

If you are sub-ohming then you will need batteries with a high max continuous discharge rate. Here is where things can get confusing because Ohm’s law is really important. All batteries are rated for an Amp output. Using Ohm’s Law take V/R to find I (or amps) since we still want a high wattage to make more vape we need a battery with a higher rated Amp.

We have a battery that most of is time at 3.7 V. We want to lower the resistance in order to increase our wattage. In turn that will increase the amount of current we draw. If we have a 3.7V battery set up with .8ohms R3.7/.8 = 4.62 amperes with a wattage of 17.11. This would be a good vape.

With a 10 Amp rated battery we would be keeping it in the safe zone, but let’s say you wanted to go with a 0.3ohm R, you would be left with a 12.3 amp draw, which is over what the battery is rated for meaning you are in the red zone. This is really bad. So at this point you would need to increase your recommended Amp rating.

If I have let out anything please feel free to comment below. This is not a complete guide on how to set up your RDA/RBA just basically a starting point and an understanding of how things work and what everything means.

And remember: BE SAFE!