Important things to know about battery safety

By Tom Pruen

About Lithium-ion batteries

 The batteries in electronic cigarettes have a chemistry that is known as Lithium-ion (Li-ion). Li-ion batteries offer extremely high energy density (they store a lot of power in a small space), which is why they have been adopted for use in small, power-hungry devices such as mobile phones, laptops and electronic cigarettes. The high energy density enables a small battery to provide a useful amount of power, but if something causes the battery to fail in a way that releases this power quickly, the results can be dramatic, and dangerous. This has been seen in rare cases with pretty much every device that uses a Li-ion battery. Li-ion batteries are most vulnerable to failure during charging, as this is when the energy density is highest, and there is an increased risk of an inappropriate voltage being applied to the battery.

Despite the dramatic nature of the way in which Lithium-ion batteries fail, they are generally very safe. Most of us own a cell phone or laptop, or indeed both, but have never experienced any issues. Similarly, there are literally millions of e-cig batteries in use, and incidents of this nature are few and far between.


Why do batteries fail?

The main causes of battery failure (aside from physical damage), are electrical shorts, wrong charging voltage or current, and thermal runaway.

Incorrect charging power is almost always the result of using the wrong charger, or power supply. The USB specification is for maximum current of 500mA, but many power supplies extend this to 1000 or more mA, for devices such as iPads. A variety of chargers and batteries are on the market, with some chargers containing the charge control circuits to control power supply and prevent overcharging, while some have this contained in the battery. Mixing chargers, therefore, runs the risk of omitting the control circuitry completely, resulting in either too high a voltage, or too high a current being supplied to the Li-ion cell. There is also then the potential for overcharging, as continuing to try and fill an already full battery will, not surprisingly, damage it.

Electrical shorts are usually a result of damage to the connector where the atomiser and charger screw in. The positive and negative poles are separated by an insulator, and this can be physically damaged, usually by over-tightening the screw fitting. If the connector is damaged, this effectively attempts to empty all the power of the battery back into the battery, causing thermal runaway.

Thermal runaway in use is usually a result of a manufacturing defect in the battery which causes an internal chemical reaction in the battery, which once started leads to an ongoing reaction which destroys the battery. This is rare, but to avoid this, you should buy batteries from a reputable vendor who has invested in quality control. It is also caused by both electrical shorts and overcharging. Physically heating a battery also significantly increases the risk of failure, and while this may seem unlikely, it’s worth bearing in mind for the summer sun.


So how can the risks be minimised?

Always buy batteries from a reputable vendor. We would particularly recommend using ECITA members’ products because this offers the reassurance that all the safety testing and compliance documentation is in place and has been checked.

Never over-tighten either atomiser or charger into the battery. Screw things in until they work, and then stop; never screw in until it is as tight as you can make it.

Always use the charger that matches the battery (don’t mix and match chargers and batteries from different brands or models)

Always use a standard (500mA) USB power supply

Do not leave batteries charging unattended! (It’s always better to be safe than sorry.)

Never leave batteries in your car (especially with good weather being on the way, hopefully)

Keep dry. (Obvious, but important!)

Check that the contacts are free of e-liquid and clean with a cotton bud or tissue if needed (added thanks to the very valid comment from Mike)

As an extra layer of safety, there are products available to place batteries in while charging (usually called Li-po bags). These are intended to contain any failure of the battery while charging, but should not be used as a substitute for all of the advice above!


This entry was posted in EU, FDA, MHRA, Safety. Bookmark the permalink.

6 Responses to Important things to know about battery safety

  1. Andy Hogg says:

    I’m concerned for safety reasons as to why you state “Always use a standard (500mA) USB power supply”?

    I use an expensive multi-port powered USB hub for charging all my USB devices, which is rated for 2100mA per port.

    I’m a heavy chain vaper that goes through about 2 * 1100mAh batteries a day. I’ve been vaping for over 3 years, and have always used this powered USB hub for charging my e-cig batteries – along with all my other USB devices.

    When I read the details of this story of the battery exploding in the pub, I’m starting to get very worried about this claimed need to “Always use a standard (500mA) USB power supply”.

    Members of the ECITA also sell USB adapters that rated much higher than 500mA – for example (but there are many others):

    Are there any technical reasons as to why using a USB charger rated over 500mA is unsuitable? – And if it is, why are ECITA members selling “universal” chargers that deliver over 500mA?

    In the case of this pub-exploding-battery story, lets assume that the charger being used was a genuine Apple 2.1A USB charger. How could that be the cause of a battery exploding?

    Should vendors (members of ECITA) be allowed to sell chargers rated over 500mA?

    USB is universally used as a charging port, and a large number (perhaps a majority) of USB chargers provide a lot more than 500mA – If electronic cigarettes are not safe to be used on chargers that supply more than 500mA, then should e-cigarettes be using the USB standard?

    I was extremely disappointed to read the response from Totally Wicked/Joyetech:

    A spokesman for the manufacturer of the battery said: “We provide clear information on websites and in electronic cigarette starter kits that explain how our batteries should be charged and cared for. We cannot comment on the circumstance of this particular instance or make any comment on the provenance of this battery. However, it does not appear that a dedicated electronic cigarette charger was used.”

    I realise that Totally Wicked are not a member of ECITA, but I believe it’s unacceptable that they are so blunt to disassociate themselves from the incident in a manner of ignorance and incompetence. They should be taking the incident seriously and investigating the cause. – As a heavy user of e-cigarettes, I want to know how and why a reputable brand battery would explode like this.

    For fear that this reply of mine is so long, that you might forget my main question: Why is it not safe to use a powered USB hub to charge my e-cig batteries?

    Many thanks,


    • admin says:

      The advice to use a standard USB power supply is really aimed at people who don’t understand their hardware, as another layer of safety.
      If you know that your charger controls the current, it’s entirely safe to connect it to a power supply that delivers more than 500mA.
      If you are unsure if it does or not, you should only use a 500mA power supply.
      The vast majority of chargers do control the current (it’s an important function when charging a Li-ion battery), but in a small number of products, these controls are in the battery itself, and the ‘charger’ is basically a USB to 510 thread adapter, which is why it’s important not to mix and match.

      • Andy Hogg says:

        The sellers should make it clear in technical specifications if the products contain charging circuits in the batteries or in the charger – and they should not be described as “universal” if they are not.

        If consumers aren’t told, how are they to know if their Joyetech Ego Charger, Kanger Ego charger, or Liberty Flights Ego charger contain a charging circuit?- It’s not specified anywhere – are consumers expected to take the unit apart and examine the electronics to work out if it controls the current? – I am capable of this, and I have done this – but general consumers aren’t able to do this. – Yes it’s true that the number of e-cigarettes exploding is very minimal, and I accept that every case may well have been user error. – but if they are led to believe that these devices are “universal” – they will use them in other “universal” USB power supplies.

        It seems to be inevitable that the government will have to enforce regulations to make things like this clear. – But as the ECITA, you should be putting these industry self-regulations into place – to show that this industry is a responsible and safe one.

        • Andy Hogg says:

          Just to add: I’m a very passionate vaper. – and I am saying these things because I care about the industry surviving! – as it is! with minimal regulation! – In this particular case, I believe the self-regulation needs to be stepped up a gear.

        • admin says:

          The problem here is that while ECITA members products are carefully examined, there is nothing to stop people using them with in any combination with products from elsewhere. We would take the view that anything identified as a charger MUST contain current control circuitry (otherwise it is not a charger), but our views only affect those who have signed up to our standards. If people are using only ECITA member products (or non member products of equal quality), we would not anticipate this being an issue at all, but this is often not the case, and is beyond our control.

  2. Mike says:

    Excellent safety advice, please add in something about keeping the contact points cleaned and free of juice deposits with the aid of cotton buds before charging too, thanks.

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