Battery Safety - The Complete Guide

Battery safety! It's something we hear about a lot in vaping but what is battery safety?

Today I will be going over, in detail, everything you need to know when it comes to your external (removable) and internal (built-in) batteries: what to look out for and how to maintain them.

I want to start by saying that while the batteries used in vaping (lithium-ion) can be volatile under the right circumstances, by far and away the biggest danger to your batteries - and therefore yourself - is negligence. With some common sense and minimal care, you should never come across any real danger with your batteries. Due to the nature of this post, we’ll be discussing some worst-case scenarios but don’t let this discourage you from exploring different devices or vaping in general. Simply bear these in mind and take the appropriate care.

When looking for external batteries, you want to make sure you buy quality batteries from a reputable source. Don't go buying batteries from eBay & don't go using your mate’s old batteries that have been sitting around for years. Quality extends to internal batteries as well: make sure you’re using a quality charging cable and a quality wall adapter or other power sources. Battery Mooch is a well-known and highly respected reviewer of batteries for vaping. If I need an opinion on a battery or information about batteries in general, Mooch is the first person I go to. You can find Battery Mooch on YouTube, Facebook, Reddit and other forums.

Before we charge in

Alongside buying your external batteries from a reputable source, you will also want to get yourself a dedicated battery charger. Charging your external batteries through your device regularly will drastically shorten the lifespan of both your batteries and device and any damage caused by use of the onboard charging can, and will, void your warranty. The onboard charging of devices does not match the capabilities of an external charger; being able to charge the batteries the way they like to be charged and possibly even recover an over-discharged battery (we’ll touch on this soon). Even with devices that do claim to offer balanced charging, you will find that it can’t hold a candle to a good quality charger. A side perk of using an external charger is that you’re almost forced to inspect your batteries for any physical damage when removing them from your device, getting ahead of any risks there. It also allows the use of multiple sets of batteries, charging your flat ones while you’ve got some fresh ones good to go.

A quick note on charging both your internal and external batteries: it is advised to avoid charging overnight or when you will be absent for an extended period of time. On the off chance that something does go wrong, you want to be nearby to handle it. It can also reduce the lifespan of your batteries. Lithium-ion batteries don’t particularly like being stored at their absolute maximum capacity for long.

You’ll want to avoid over-discharging (or deep discharging). Over discharging is when the voltage of your battery drops below 2.5-3 volts (it will differ depending on the battery). Most modern regulated devices will have protections against this but if you run your batteries completely “dead”, you will want to recharge them pretty soon. Allowing them to sit at “dead flat” for an extended period of time can send them into over-discharge. Over-discharge can be unrecoverable if severe enough, even by chargers that have over-discharge recovery.

Things are heating up

Environmental factors, such as temperature, can have a big impact on your batteries and device. Lithium-ion cells must not be charged in conditions above 45 degrees or discharged (used) above 60 degrees. Australian summers can get quite warm. Leaving your batteries, for example, in your car for an extended period of time can exceed the 60-degree safety limit of the battery quite quickly. Leaving your batteries in a shaded, cool place is ideal in these types of conditions, as being exposed to extreme heat can lead to your battery swelling up and possibly even venting. Leaving batteries in your device in conditions such as these pose a severe risk to your battery, device and yourself. Even in the absence of a catastrophic failure, swollen batteries can become stuck in the device, leading to both need to be safely disposed of and replaced. If you are needing to store your batteries or device in the car throughout the day, it may be worth investing in a thermally protected container, like a cooler bag or small esky. If you do this though, avoid putting your vape with other cold items that may provide excess moisture.

Water is another thing to watch out for. I’m sure we all know the hazard that water poses to electronics but water is also a danger to batteries themselves. If water gets inside the battery, it can damage the internal electrical and safety components, and destabilise the chemical components. 

The final thing concerning both internal and external batteries is disposal. After your battery has valiantly given its life for the cause or meets an untimely death, it’s time to get rid of it. Don’t throw it in the rubbish, or even the recycling, though. This goes for all batteries used for everything. Batteries that end up in landfills are a fire risk and often leak toxic chemicals into the environment. Batteries need to be recycled but recycled properly. Some companies like Aldi and Battery World accept some batteries for disposal or you can take them directly to your nearest recycling centre. If you’re unsure, drop off your used devices or batteries into your local Super Vape Store and we’ll safely dispose of them for you.

Everything else from here primarily applies to external batteries. Those with internal batteries may have an early mark but are welcome to stay if you’re thinking of upgrading or just want to learn.

Will you marry me?

The most common batteries found at most vape stores are 18650 & 21700. Fun fact: the numbered name of these batteries denotes their physical size. An 18650 is 18mm wide x 65mm tall and a 21700 is 21mm wide x 70mm tall. This applies to all batteries named under this convention. 

Most devices will take either 1 or 2 batteries but it’s a good habit to have some spares. If your device needs 2 (or more) batteries, it is always recommended to use “married” batteries. This means that you want to use 2 of the same type of battery, brand, model and capacity that have been bought, charged and discharged at the same time. You can use the same married pair between different devices, just be sure to keep the pair together. 

The reason for this is to avoid using ‘unbalanced batteries’. Unbalanced batteries refer to having a pair of non-identical batteries or a pair of identical batteries that are at different points in their lifecycle. This can happen when you have a married pair and separate one to use on its own, then attempt to use it with its previously married partner. You will find that the battery you have been using on its own will not last as long between charges as the one you haven’t used. Another factor that could cause unbalanced batteries is charging your batteries through your device, frequently, for a considerable length of time.

The danger of unbalanced batteries comes down to using them. Your device is expecting that each battery is as capable as the other and attempts to split the load, evenly, between them. If you have one battery that is further discharged than the other, it may be placed under conditions that exceed its safe limits.

To avoid this, I would recommend using a married pair together, indefinitely, and grab yourself spare single batteries to use in any single battery device you wish to use.

Damage, flextape cant fix this

Probably the easiest thing to keep on top of is physical damage to your batteries. If you notice your batteries are damaged, whether it be a slight nick or a massive dent you MUST stop using the battery and replace them. Using a damaged battery poses a severe risk to yourself. External damage can indicate that internal damage has occurred as well.

If it is just a torn wrap (the plastic covering on the battery), you can replace this yourself. See below for a tutorial. When replacing the wrap, make sure you keep hold of the insulation ring, as wraps do not typically come with a spare. It’s also a good idea to grab some spares of this, too. The insulation ring should be placed around the positive terminal at the top of the battery. Both the wrap and insulation ring separate the negative and positive terminals of your battery. Without the insulation ring and/or wrap, your battery is beyond unsafe and should NOT be used under any circumstances.

To replace a damaged wrap:

  1. Remove the damaged wrap, keeping track of the insulation ring as mentioned. If you need to use a tool to help get it off, use something blunt and non-conductive, like plastic or ceramic tools.

  1. Open the new wrap and slide it over the battery, leaving the same amount of room on both ends.

  1. Place the insulation ring over the positive terminal.

  1. Using a back and forth motion, heat the wrap using a hairdryer or heat gun, leaving 10-20cm between the heating tool and battery. Keep going until the wrap has fully shrunk.

Tada! You have a freshly wrapped battery. Take the rest of the arvo off. Before using your nicely wrapped battery, allow it to cool. A few minutes should be sufficient.

Side note: for the love of all that is holy - and I really cannot stress this enough - do NOT use a lighter to rewrap a battery. Not only do you risk burning through the wrap, making the whole process pointless, but you risk catastrophic internal damage to your battery, putting yourself in danger.

Below I have included a photo of 2 different battery chargers. The one on the left is an Efest Mega and the one on the right is a Nitecore SC2. The Efest Mega charger fits 18650s and 21700s with room to spare. However, the Nitecore SC2 will comfortably fit 18650’s but is a tight squeeze for 21700s. This limited space is a risk to your wraps when you go to put your batteries in and take them out. Take care when it comes to buying a charger if you use 21700s; you don't want to be cramming your battery in.

The battery positioned on the Nitecore SC2 demonstrates the type of damage that can occur.

For any spare batteries that you want to take with you during the day, you will want to grab yourself a case; plastic, felt, silicone or otherwise. Not only will this protect your batteries and wraps from any physical damage but it will also prevent your batteries from making a connection. 

Accidental dropping or misuse of your device can lead to damage to your batteries as well. Also, never taking your batteries out of your device to charge them can dent the terminals due to the prolonged pressure from the contacts. In extreme cases, internal charging can also lead to swelling or venting.

Time to vent (well, hopefully not)

We’ve mentioned venting a few times now without really discussing it because it’s worthy of its own section. Venting is kind of the absolute worst-case scenario with batteries. Venting is the release of gasses during catastrophic failure, following a process called thermal runaway. Believe it or not, venting is actually what you want to happen in this scenario. Should anything happen to prevent venting from happening properly, it can lead to fire or explosion. If your battery does start to vent, the telltale signs are extreme heat, a hissing sound, a yellowish mist coming from the battery and an awful smell resembling rotten eggs. The smell, sound and mist are gasses escaping from your battery. These gasses are toxic and flammable. The gasses being flammable is the biggest danger here. Not only can they ignite from any heat or electrical sources in the environment but the heat from the battery can ignite these gasses if not handled appropriately. That’s why it’s crucial to store venting batteries in an open container that won’t ignite or melt and allows for high air circulation. This is, ideally, outside.

After your batteries have vented, you should NOT attempt to use them under any circumstances. Safely dispose of them when you’re certain that the venting has finished and the heat has dissipated.

If you believe your battery is venting, you have a few options:

1a. Ideally, you will want your device/batteries to be in a metal or ceramic container, without a lid, including a sink basin. When transporting your venting batteries, take care of the heat and gasses. Try not to be holding them any longer than absolutely necessary or is safe. 

1b. If a sink or bathtub is viable, you can flood it. This can also be done with a garden hose and appropriate container. The water can help reduce the extent of the chemical reaction. This won’t save your batteries but can potentially reduce the risk of any damage caused to your person or environment. 

  1. If you can’t get your batteries to a safe container, your last option is to just leave them somewhere away from people, animals and flammable materials (a tile floor, concrete, dirt, sand, etc).

Leave the batteries in a safe container or place, in a well-ventilated area for at least an hour, preferably outside. Once you have sorted the location for your batteries to vent, remove any flammable items from the immediate area and then promptly leave the area. Be sure to stay nearby to observe the process in case you need to act further. It can’t hurt to have a source of water nearby, just in case, and do not hesitate to call the emergency services if the situation escalates. They would much rather respond to a non-event than be called too late.

Thanks to the smell and toxic nature of the escaping gasses, you’ll want to do some heavy cleaning of everything in the surrounding area after you’re absolutely certain that the venting has ended, especially if there will be young children and/or animals in the area. If you have some, kitty litter in a sock is an old trick that may help soak up some of the gasses and smell lingering in the air. Leave that in the area for a day or 2.

Anyway, enough doom and gloom. Time for some numbers. This last section is mainly for rebuildable users. If you don’t use rebuildables or don’t intend to, you may exit stage left. 

Re: buildables

Thanks to the customisability of rebuildable atomisers, battery safety and your choice of batteries become more important. When it comes to selecting your battery/batteries, there are a few things to consider:

Battery type

Single/Dual battery


Coil Resistance

milliamp/hour (mAh)

Continuous Discharge Rate (CDR)

Type of battery: 

This one seems pretty obvious but there’s an aspect of this that often gets overlooked. If you are using a device that only takes 18650s, then you would not want to buy 21700s. However, if your device is 21700 compatible, you could also use 18650s with the appropriate adapter. Just keep in mind that you would be losing about a quarter of the potential battery life compared to running 21700s, as well as reducing your CDR (see below). 

The thing that I find gets overlooked is what I call the “low battery cutoff”. Especially if you run medium-to-high wattage, you might notice that your vape feels weaker when you still have a bit of battery left. You might even see your wattage or voltage drop when taking a hit. This is normal and the safe thing to do, as when your battery life is lower, it’s harder for the cell to maintain that higher output. With 21700s, in comparison to 18650s, this tends to happen substantially later (with lower battery). At 60-70w, on a single 18650, I typically notice the drop at 30-40% battery life remaining. On a single 21700, I’m more likely to notice it at about 10%.

mAh (milliamp/hour) and is a unit that measures electric power over time; effectively, how long you will get out of your battery. The bigger the number, the bigger the lifespan between charges.

CDR (continuous discharge rate) is arguably the most important trait to consider when looking at batteries. The CDR is the maximum continuous current - measured in amps (A) - that can be safely drawn from the battery. If you frequently exceed the given CDR, the cells will get too hot. Heat will damage the battery, reducing its overall lifespan. Overheating may even cause the cells to vent, leak, or damage your device. Ohm’s law, below, is how we figured out what kind of CDR we need to be looking for.

Fortunately, there's a rough correlation between CDR and mAh. The higher the capacity, the lower the CDR. That means devices that draw less power can take advantage of higher-capacity cells. Hungrier devices will need to use lower-capacity cells in order to safely draw more current. 

An important thing to note here: most regulated devices will have an “overdraw” protection; i,e. a circuit protection for too high of a current. However, that is a static number and does not account for the CDR of your batteries. It is easily possible to exceed the CDR of your batteries while still being under the “overdraw” limit. 

Welcome, Hohm!

Ohm’s Law 

In vaping, the main thing we need to know from Ohm’s Law is:

Current (amps) = voltage (volts) / resistance (ohms Ω)

An example of this would be an atomiser with a resistance of 0.13Ω, running at and 3.7volts:

0.13Ω x 3.7v = 30amps

While some 18650s have a CDR of 30 amps on their own, it’s generally not recommended to max out the current of your batteries consistently. For this, you would be best suited for a dual 18650 or single/dual 21700 device. 

There are a number of Ohm’s Law calculators online but the one I personally use is It is vaping dedicated and also has a bunch of other useful tools for rebuildable coils and DIY e-liquid.

Unregulated Devices!

If you intend on using an unregulated or mechanical device, everything you’ve read here becomes exponentially more important, especially Ohm's Law, battery health and wrapping, and knowing your CDR. With unregulated or mechanical devices, you will be eliminating most or all of the circuit protections and the ability to adjust the power. While this sounds quite dangerous - and it certainly can be under the right conditions - it can be handled safely when applying due care, patience and knowledge.

To sum it all up, this blog post is here to highlight the potential dangers of lithium-ion batteries and warn you ahead of time and help you prevent anything bad from happening. It is by no means a common occurrence for batteries to have a catastrophic failure, especially without user error, but this information is here in the hopes of making it even less common.

Happy vaping, stay safe and I hope you found this post informative and helpful. 

- Super Vape Store Charlestown


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