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A Buyer’s Guide to E-Cigarette Batteries: Battery Jargon Explained!

A Buyer’s Guide to E-Cigarette Batteries: Battery Jargon Explained!

John Boughey |

 Last fact-checked 25 April 2024

Don’t know your 21700s from your 26650s? No idea what mAh means?You’re not alone! For new vapers, nothing is more confusing than batteries.

In this simple buyer’s glossary we’ll help you understand everything you need to know about vape batteries. We'll explain the main types of e-cigarette battery, and show you what all the different technical terms actually mean.

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    Every Vaper Needs To Understand E-Cigarette Battery Jargon!

    E-cigarette batteries can be dangerous if they’re used incorrectlyVape devices and components are well regulated in the UK (see, but they're powerful. If you’re using a good box mod or vape pen you’ll very rarely run into any sort of trouble. Still, you’re carrying around a battery with enough power to light a small fire — the more you know, the safer you’ll be

    A solid knowledge of how e-cigarette batteries work will save you money in the long run, too. If you’re planning to vape for a long time, you can expect to go through a lot of batteries. You want to squeeze every last drop of efficiency out of the batteries you buy. One way to do that is to understand the different properties listed on the product description pages. That way, you can pick a battery that suits your device and style of vaping perfectly


    What’s the difference between the different types of e-cigarette battery?

    E-cigarette batteries are all the same shape (cylinders with flat ends — they don’t have a button terminal at the + end like an AA or AAA battery).

    The most popular types of battery in the UK are 18650s, 20700s and 26650s. As of April 2024, 18650s outsell all other battery formats by a significant margin, and are fast becoming the industry standard.

    Here’s a quick table showing the differences between of each type of e-cigarette battery: 

    Battery Type Diameter ⌀ Length ⇤ ⇥
    18650 18mm 65mm
    20700 20mm 70mm
    21700 21mm 70mm
    26650 26mm 65mm

    As you can see, name of each battery matches up with its physical size. The first two numbers in the name match the diameter (in millimeters), and the next three numbers match the length (in tenths-of-a-millimetre).

    This is why it’s so important to get the right battery type for your vape device. If you get the wrong type, it literally won’t fit in your mod.

    E-cigarette battery terms you need to know

    As a minimum, you should know what size, voltage and capacity you need in your e-cigarette battery. There are other terms that you should familiarise yourself with, too. Here’s a list of the terms you’ll usually see when browsing our e-cigarette batteries department:

    Nominal Capacity (mAh, or milliAmp hour)

    mAh tells you how many ‘hours of power’ you’re going to get out of an e-cigarette battery. Most e-cigarette batteries have a capacity of anywhere between 2,000 and 4,000 mAh. You don’t hold the fire button down for the whole time you’re vaping — you usually just heat your coil for a few seconds at a time — so don’t worry too much if you can’t buy a battery with a massive mAh rating. You’ll still get a lot of vaping done on a 2,000 mAh battery.

    Nominal Voltage (V, or Volts):

    The Nominal Voltage is the ‘normal’ amount of voltage that you can expect from your battery. A fresh battery might start out with a higher voltage than the nominal voltage, but as the power is drained from that battery over time, that voltage will naturally start to decline. Nominal voltage gives you a reliable ‘average’ value that you can rely on for most of your battery’s lifespan. Most e-cigarette batteries run on a nominal voltage of 3.7V.

    Discharge Voltage (V, or Volts):

    The Discharge Voltage, also known as the Minimum Voltage, is the point at which you should stop using your battery and recharge or recycle it. If you continue to use a battery after its voltage has dipped below the stated discharge voltage, you risk damaging the battery. You’ll usually notice the drop in voltage as your battery runs out — you’ll get weaker vapour and less crackle. The safety chip in a good box mod will often give a warning and/or cut out completely just before your battery reaches its discharge voltage. 

    Discharge Current (A, or Amperes):

    Discharge Current is the ‘normal’ current strength that you should run your battery at. In theory, if your vape device is running at the exact same number of amps as the discharge current of your battery, you will get the exact number of ‘hours of power’ promised in the Nominal Voltage. If you run your vape device below the discharge current, you should get a little bit longer out of each battery. 

    Max Continuous Discharge Current (A, or Amperes):

    The Max Continuous Discharge Current tells you how many amps you can safely squeeze out of a battery … but all bets are off on battery life if you rely on this number. If you run your vape device at the same number of amps as the battery’s max continuous discharge current, you won’t be risking anything from a safety perspective, but you’ll go through batteries much much faster than someone vaping at or below the discharge current

    Pulse Discharge Current (A, or Amperes):

    The Pulse Discharge Current tells you how far your battery’s manufacturer thinks you can push your battery in a single short pulse. We’re a little uncomfortable with pulse discharge current, because a ‘pulse’ isn’t very clearly defined. For instance, some manufacturers might consider a single split-second camera flash as ‘one full pulse’, but vapers will often push and hold the firing button on their e-cigarette for three seconds or more. Our advice is to never go beyond the max continuous discharge current, unless you’re a very experienced vaper with a solid understanding of electrical engineering. 

    Max Charging Current (A, or Amperes)

    The Max Charging Current just tells you the safe current that you can charge your batteries up at. Rechargeable e-cigarette batteries can’t take energy in as fast as they put it out. If you try to charge a battery at a higher amp rating than its max charging current, the battery won’t charge any faster, but it will heat up and it could become a fire hazard. When buying rechargeable batteries, you should always try to match the charging current of your charging device. Some chargers have a switch or dial that allows you to set the charging current — see our full range of battery chargers here.

    Discharging Temperature Range:

    The Discharging Temperature Range is simply the temperature at which your battery will work safely. Most e-cigarette batteries have a discharging temperature range of between -20°C and +60°C (written as -20-60C). In the UK, you might think that -20-60C is more than enough for us. In most cases it is, but just bear in mind that the internal temperature of a battery is likely to be much hotter than the external temperature when the battery is hard at work. To stay safe, our advice is to always use a regulated box mod (i.e. one with a safety chip), vape at a safe current, and go for a battery with a high temperature range.

    Safety Note: Bear in mind that, to vape safely, you need to understand voltage, current and resistance. Your battery needs to work safely with your heating coil. To learn more about coil resistance and how it affects your voltage and current settings, please read our Ohm's Law article.

    We hope this battery buyer’s dictionary comes in handy. If you’re still confused by anything, please please get in touch. We’ve sold a lot of batteries over the years, and I’m an electrical engineer, so you can rest assured that you’ll be getting good advice.

    Stay safe and happy vaping!

    John Boughey


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