Update: Feb 2021
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, while we were writing this post, we had at least five emails from readers asking for an explanation!
So we’ve put together this tutorial for our E-Cigarette Academy. Before we get started, it’s worth noting if you are starting off with variable voltage/wattage, and even with different resistance coils, 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 or wattage of the battery until you get the vapour, flavour and throat hit you desire. You can also experiment with using different resistance coils and combining them with different voltages/wattages.
After all, with most entry-level vape kits, all you need to do is:
- Check what wattage you can use with the coil in your device
- Adjust your wattage and airflow until you get the vapour, flavour and throat hit you need.
Some people want to know more to get the perfect vaping experience. If you’re one of them, this post is for you.
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
- Amps – electrical volume
- Volts – electrical pressure
- Watts – measurement of total amount of electricity consumed
- Ohms law
What Are Ohms? A Simple Explanation for Vapers
An ohm (Ω) is a unit of resistance. Essentially, the lower the resistance of your coil, 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 coils)
- 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
- vape juice will be used more quickly
- coil 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 coil the opposite will happen:
- less electricity flow
- reduced coil heat
- reduced amount of vapour
- cooler vapour
- and you may experience a less intense flavour.
But on the plus side:
- battery life will be longer
- less e-liquid will be used
- you will be less likely to get a dry hit.
What Ohm Resistance Should I Use In My tank?
When we first wrote this post, we used to refer people to the chart above.
While we’ve left the chart there, our answer has evolved!
- new technology has entered the market
- more vapers Mouth-to-Lung with low resistance devices
- subtle differences in materials used can affect the wattage needed
- manufacturers provide better coil guidance.
So unless you are making your own coils, check the manufacturer’s guidance. You can find this on product manuals and our website product pages.
Variable Voltage and Wattage Vapes Explained
The resistance of your coil is not the only thing that affects vapour, flavour and throat hit. It also depends on the amount of power flowing through your coil.
There are two common types of vape batteries which allow different amounts of power to flow through your coil. These are variable voltage and variable wattage.
As we’ve seen, you can get a more intense experience by lowering the resistance of your coil.
You can also do the same by increasing the amount of power flowing through your vape device. That may sound complicated, but usually there’s nothing more to it than pressing an up/down button.
But what if you want more vapour again?
Then you can combine a low resistance coil with a higher wattage to get even more vapour. But this does come with its own problems. You are far more likely to burn coils or get a dry hit, and coil life is reduced.
Variable Voltage vs Variable Wattage Vapes
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.
A variable wattage device is different. 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 your vape 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 that 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.
If you change the coil to a higher resistance of 2.8ohms you will notice a considerable decrease in flavour, vapour production and heat. That’s because the wattage is lower (around 4.4 watts). You will need to increase the voltage to increase the wattage and get a better vape.
Because lower resistance coils use more wattage, they tend to generate more heat. This means they often burn out quicker than a higher resistance coil would.
Variable voltage devices are quite rare now, although many devices will display both voltage and wattage. The Innokin Coolfire Z50 is an example of a variable wattage device, and delivers 6-50 watts controlled by up and down buttons.
What Does mAh in Vape Batteries Mean?
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?
We’ve seen that by lowering resistance and increasing voltage we get more vapour, more throat hit and sometimes more flavour.
Sub-ohming takes this further by vaping at a resistance of less than 1 ohm.
At one point this was considered pushing the boundaries of vaping. But things have changed.
The term sub-ohm, while still used, is not as relevant as it used to be. Coils below 1 ohm are common, and coils with a resistance of 0.8 ohms are often used for Mouth-to-Lung vaping. Even lower resistance coils, such as 0.15 coils, are often used for cloud vaping.
Originally, sub-ohm vaping was reserved for experienced vapers who want to push the boundaries with rebuildable coils. The introduction of mass-market mods has changed all that.
For example, the Smok Morph 2 can fire up to a massive 230 watts and uses low resistance Plexus coils for larger clouds of vapour.
Vapers who want the largest clouds possible may still use a mechanical mod. These have no electrical safety switch and may increase the risk of a malfunctioning battery if not used correctly.
Want to know how to sub-ohm sub ohm? See the Vaper’s Guide to Sub Ohm Vaping.
Advanced Explanation of Voltage, Watts and Ohms for Vapers
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.
The Amp (short for ampere) is a measure of current. An ampere is defined as 6.241*10 18 electrons (1 Coulomb) per second passing through a point in a circuit.
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.
Watt is a measure of the amount of power consumed by an electrical device.
Ohms Law for Vapers
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.
For those who prefer video, here’s a stellar explanation from New Amsterdam Vape.
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.
Sub Ohm Hardware
We’ve already mentioned the iStick Power and the Innokin Plex kit, both of which can be used for sub-ohm vaping. But if you’re looking for an all in one kit, you might want to consider the Innokin MVP5.
One of my favourite vape devices, the Innokin MPV5 can output up to 120 watts. Sure, there are devices with more power, but the reality is that unless you are building your own coils, you don’t need more than 120 watts of power.
For a fixed battery device, this MPV5 has an unmatched capacity. At 5200mAh, this device can last for days without needing to be recharged/ on one charge. It also provides a great vape, and contains a whole host of unusual features such as flashlight functionality and the ability to act as a power bank.
The best current tank for clouds is the Falcon II. The device comes with 0.14ohm coils and a conical mesh design which funnels air-flow up through the coil for serious clouds.
There’s a lot to take in here, but this information is really for the enthusiast. Unless you’re into coil building, you don’t need a deep knowledge of the science to vape.
The most important thing is to learn just enough about vaping to ensure you enjoy it – and don’t go back to smoking.