Not so long ago a reader told me she was still completely confused about voltage, watts and ohms, and I have a feeling she’s not the only one. (In fact, since Tom and I started writing this post, we’ve had at least five emails from readers asking for an explanation!)
Before we get started, it’s worth noting if you are starting off with variable voltage, and even with different resistance atomisers, you can get a very good vaping experience without a deep understanding of the science behind it.
At its simplest level, it’s simply a matter of adjusting the voltage of the battery until you get the vapour, flavour and throat hit you desire. You can also experiment with using different resistance atomisers and combining them with different voltages.
Some people want to know more, though, in order to get the perfect vaping experience. If you’re one of those, this post is for you.
When we started writing this post, we did find that it was rapidly getting complicated. Getting a balance between a really good explanation of the science and something that everybody could understand was proving impossible. So we’ve created two parts to this blog post: A Introduction to Voltage, Watts and Ohms as well as a more advanced explanation which covers Ohms Law.
An Introduction to Voltage Watts and Ohms
- Resistance (Ohms)
- Which resistance should I use?
- Variable Voltage
- Variable Voltage vs Variable Wattage
- mAh Explained
- Sub Ohming
- Amp Hour (Milli Amp Hour (mAh)) – Battery capacity
- Volts – Electrical Pressure
- Amps – Electrical Volume
- Watts – Measurement of total amount of electricity consumed
- Ohms Law
What Are Ohms?
An ohm is a unit of resistance. Essentially, the lower the resistance of your atomiser, the more electricity will flow through it. Increase the amount of resistance and less electricity will flow through. So when you use a lower resistance atomiser, and more electricity flows through, you will find the following:
- more heat is generated at the coil
- more vapour is generated
- you may experience a more intense flavour (however, flavours perform differently with different resistance atomisers)
- vapour will be warmer
Depending on your tastes, the above may all be positives! On the negative side:
- your battery will be drained more quickly
- battery life may be reduced
- e-juice will be used more quickly
- atomiser life will be reduced (very low ohm atomisers may only last 2-3 days)
- you are more likely to experience a dry hit
Obviously, when you use a high resistance atomiser the opposite will happen:
- less electricity flow
- creating a reduced atomiser heat
- a reduced amount of vaper
- cooler vaper
- and you may experience a less intense flavour
But on the plus side:
- battery life will be longer
- less ejuice will be used
- you will be less likely to get a dry hit
Want to know how to sub ohm? See the Vaper’s Guide to Sub Ohm Vaping.
What Ohm Resistance Should I Use In My Clearomiser?
There’s no one answer (although the sub-ohm chart above may help) – it depends on you, the vapour and throat hit you prefer, as well as the voltage you combine with the ohms.
You’ll also find that different e-liquids react differently, and that the resistance used has a big impact on flavour, so it’s definitely an area for experimentation. For further information on how to use different resistance clearomisers see The Ultimate Guide to Clearomisers
Variable Voltage E-Cigs Explained
The resistance of your atomiser is not the only thing which controls the amount of vapour, flavour and throat hit that are produced. It also depends on the amount of power flowing through your atomiser.
There are two common types of ecig batteries which allow different amounts of power to flow through your atomiser, which are known as variable voltage (such as the Vision Spinner 2 or the Evod Variable Voltage) and variable wattage.
As we’ve seen, you can get a more intense experience by lowering the resistance of your atomiser. You can also do the same by increasing the amount of power flowing through your e-cigarette. That may sound complicated, but usually there’s nothing more to it than pressing an up/down button or rotating a dial.
But what if you want more vapour again? Then you can combine a low resistance atomiser with a higher voltage to get even more vapour. But this does come with its own problems – you are far more likely to burn through atomisers or get a dry hit, and atomiser life will be dramatically reduced. Also see The Ultimate Guide to Batteries and The Vision Spinner VV: A Tutorial.
Variable Voltage vs Variable Wattage Devices
Essentially, the difference between variable voltage and variable wattage is a bit like the difference between an automatic and a manual car. With a variable voltage device you manually control the amount of power (voltage) going through your device.
The amount of energy that is actually output will depend on how the resistance of your atomiser interacts with that power flowing through it. With a variable wattage device, however, rather than telling the device how much power you want to flow through your atomiser, you tell it how much power (wattage) you want it to output. The variable wattage device will then automatically adjust the power going through the atomiser (the voltage) to produce the power output you need (the wattage).
To put it another way, watts is essentially how much power the e-cig produces and voltage is how much power is put through the device. So, as you increase the wattage the voltage also increases and vice versa. Voltage is not the only factor which affects wattage – you also need to take into account the resistance of the coils. Lower resistance coils produce more flavour, vapour and heat at a lower voltage than higher ohm coils because they use more watts.
For example, if you have a 1.8ohm coil running on 3.7 volts you’ll get an output of around 7.3 watts – a decent vape. However, if you change the coil to a higher resistance of 2.8ohms you will notice a considerable decrease in flavour, vapour production and heat, as the wattage will be lower (around 4.4 watts) and you will need to increase the voltage to increase the wattage and thus get a better vape.
Because lower resistance coils use more wattage, they tend to generate more heat and can burn out quicker than a higher resistance coil would. [Currently we only provide variable voltage devices online, but you can purchase variable wattage devices at any of our shops.]
What Does mAh in E-Cig Batteries Mean?
You’ve probably seen mAh used to describe electronic cigarette batteries. mAh is important because it measures how long a battery lasts. Going back to our car analogy, if voltage is the fuel then mAh is the size of the fuel tank – the bigger the tank the longer the car will go before it needs refuelling. mAh stands for Milliamps per hour, but we’ll go more into that below.
What Is Sub Ohm Vaping?
So, we’ve seen that by lowering the resistance and increasing the voltage we get more vapour, more throat hit and sometimes more flavour.
Sub-ohming takes this to extremes by vaping at a resistance of less than 1 ohm. While this can produce massive amounts of vapour, it also puts stress on both the battery and the coil in your clearomiser.
It’s often done on a mechanical mod, which has no electrical safety switch and may increase the risk of an exploding battery if not used correctly. Until recently, sub-ohm vaping has been reserved for experienced vapers who want to push the boundaries with rebuildable atomisers.
Advanced Explanation of Voltage, Watts and Ohms for Vapers
Electronic cigarettes are incredibly simple circuits that contain a battery, a switch and a heating coil. The circuit is effectively a controlled short, with the power being output from the battery being used to create heat.
A milliampere hour (mAh) is 1000th of an ampere hour (Ah). Both are used as a measure of battery capacity, a higher mAh rating means more capacity. mAh only measures capacity and should not be confused with power.
Voltage is the amount of potential energy between two points in a circuit. One point will have more charge than the other. This difference in electrical charge between the two points is called voltage.
Image above from sengpielaudio.com Ohms law refers to the calculations used to show the relationship between voltage, current and resistance. There are three of them, which we’ve listed below.
- V = Voltage measures in volts
- I = Current measures in amperes (Amps)
- R = Resistance measured in ohms
By knowing any two of the three values, you can calculate the third using ohms law;
- V = I x R (Voltage = Current Multiplied by Resistance)
- R = V/I (Resistance = Voltage divided by Current)
- I – V/R (Current =Voltage Divided by Resistance)
So, if you are using a 0.5ohm coil on a battery that gives 4.2 volts, you use the following sum to work out how many amps the circuit is draining from the battery.
I = 4.2/0.5 = 8.4A
This is useful for vapers to know, particularly if they are making their own coils. The sum above is the most useful, as you should not be vaping on a coil when you do not know its resistance, or on a battery with unknown voltage output.
You’ll find an excellent calculator which you can use to calculate ohms law here. Update: Shawn Hoefer has suggested also using the Ohmaster and CigToy apps. Given the importance of battery safety, he recommends using both rather than one or the other.
There’s a lot to take in here, so we’ve created a PDF version which can be downloaded to your computer and printed. Just click the image below!