Battery safety

Discussion in 'Vapor Related Equipment' started by Jack Sprat, Jun 21, 2014.

  1. Jack Sprat

    Jack Sprat Well-Known Member

    With all the battery powered portables on the market, and people looking for DIY replacement batteries, perhaps a batteries safety sticky would be useful. Li-ion batteries can catch on fire or explode if the wrong one is used, or if they short out.
  2. CrimsonKing

    CrimsonKing The Destroyer Of Worlds

    For Ecigs so there is probably a decent amount about ohms law and such that doesn't apply as much here since we are not building our own coils (just copied and pasted) but still good info about the rechargeable the vapes are using.

    So you’ve picked up a safer chemistry battery and know how to avoid the most likely scenarios where a battery could go boom. This isn’t the whole picture though, and the reason for this is that a given battery can only provide so much current. If you ask it for more than it can give, you’re running the very serious risk of suffering a battery failure.

    As with many aspects of e-cig safety, all you need to stay safe is a little bit of information and an understanding of how it applies to vaping. Plus, in most cases – aside from when sub-ohm vaping is concerned – it is unlikely to be a problem.

    Key Points

    • Ohm’s law says that current = voltage / resistance, and your battery can only provide so much current.
    • The maximum current allowable for a given battery is listed in amps as the maximum continuous discharge rating, or calculated from the “C rating” multiplied by the battery’s capacity.
    • For AW IMR batteries, the 2000 mAh 18650 can provide 10 amps (A), the 1600 mAh 18650 can provide 24 A, the 1100 mAh 18490 can provide 16.5 A and the 700 mAh 18350 can provide 6 A. If you’re looking for maximum amp draw, the Sony US18650VCT4 (or VCT3) offers up to 30 A.
    • For maximum safety, choose a larger battery and keep any coils you build over 0.8 Ω, unless you’re willing to do the math and understand the risk of battery failure (but lower resistances are rarely needed).
    • VV/VW devices have protection built in, so if you’re using a mechanical e-cig mod, the best advice is to fit a safety fuse and ensure you know the batteries limits.

    Do you have any advice for people interested in sub-ohm (resistance < 1 ohm) vaping with regards to battery safety?


    Wear a helmet :)Steve K (Steve K’s Vaping World)



    If you’re into sub-ohming or want to get into it, it’s important to know about the resistance you’re building, that you don’t have a short, and the amp draw it will require. This is why I recommend only two batteries at this point, the Sony us18650vct3 1600 mAh and the Sony us18650vtc4 2100 mAh. Are there others you can use? Absolutely! But since these have the highest amp rating of any battery I know, 30A, it’s what I like to recommend.

    Remember, the only thing that should be getting hot is your coil! – Phil Busardo (


    Sub ohm vaping is all about AMPS, don’t ask more from your batteries than they can handle. The website is incredibly useful to figure out how many amps you are requesting from your batteries. – Nick “GrimmGreen” Green (


    Despite claims, and often paperwork, to the contrary, many overseas suppliers supply batteries without overcharge protection. Good retailers get their own testing done in their own country – so look for evidence that the batteries have been certified in your country as well as at the point of manufacture. We also batch test batteries by overcharging them in an explosion proof container. – James Dunworth (E Cigarette Direct)

    Ohm’s Law for Vaping

    Learning about Ohm’s law is essential if you’re getting into e-cig mods, but there are plenty of useful calculators you can use if you’re allergic to math. The rule basically describes the relationship between voltage, resistance and current.

    Think of these three quantities like a flow of water down a hosepipe connected to a faucet. The voltage is the raw input energy supply; analogous to how much you’ve opened the faucet to start the water flow, and the current is the flow of the energy; analogous to the speed the water flows down the hosepipe. Resistance is like friction for electronic current, like the bumps and irregularities on the inside of the pipe that slow down the flow of water.

    Ditching the analogy, the voltage is the difference between charges at either end of the circuit, the current is the measure of how much electricity is flowing and the resistance (of the conductive material) opposes the flow of electricity.

    Current is equal to voltage divided by resistance. Mathematically, it looks like this: I = V / R, where I is current (measured in amps, A), V is voltage (measured in volts, V) and R is resistance (measured in ohms, Ω).

    Although resistance converts the electrical energy into heat (warming your atomizer coil and vaporizing your juice), current is the most important factor when it comes to vapor volume. If we set the voltage at 4 V, a resistance of 2 Ω would offer 2 A of current. If the resistance is increased to 3 Ω, the current drops and therefore your coil doesn’t heat up as well (4V / 3 Ω = 1.3333… A).

    Of course, the math isn’t always this easy when decimal values of voltage and resistance are involved, but any calculator (even the one on your computer/cell phone by default) takes the mental arithmetic out of it.

    E-Cig Mod Battery Limits and C Ratings

    With this information alone, you’d be forgiven for thinking that you want to pump the voltage as much as possible and keep the resistance to a minimum. However, you run into issues because any battery can only supply so much current. This is given by the maximum continuous discharge rating of the battery (there is a burst discharge rating too, but this is inapplicable to vaping), which is an amount stated in amps.

    Here’s a handy list of the amp limits of the most common vaping batteries, including AW IMR 18650s, 18490 and 18350 batteries. For example, an AW IMR 18650 with a capacity of 1600 mAh (a measure of the number of amps a battery can provide over time before it needs recharging – this will be listed on the body of any battery) can handle 24 A, and an 18350 with 700 mAh can handle 6 A of current.

    If – for whatever reason – you can’t get hold of the amp limit for your battery, you can calculate it easily based on the C-rating of the battery. To turn this C-rating into a continuous current draw limit, you simply multiply it by the capacity of the battery and then convert the result (which will be in milliamps, 1/1000 of an amp) into amps.

    So for the AW IMR 18650 with a capacity of 1600 mAh and a C rating of 15, the amp limit is given by 1600 mAh × 15 C = 24000 mA. Since 1 mA is 1/1000 A, 24000 mA is 24000/1000 = 24 A. If you’re within this limit, the battery can handle what you’re asking for. Keep in mind, though, that this isn’t a definitive value, just an average, so it’s better to assume the safe limit is a little lower than that stated.

    Sub-Ohm Vaping Safety

    Now the issue can be investigated pretty clearly. With an IMR 18350 battery with a maximum continuous discharge current of 6 A, it’s unlikely you’ll hit a limit unless you’re using a coil with a resistance of lower than 1 Ω. Using 1.5 Ω at 3.5 V, the amps you’re requesting comes to 3.5 V / 1.5 Ω = 2.3333… A, well within the safe usage limits of even the small battery.

    When you drop the resistance to 0.5 Ω, you’re requesting 3.5 V / 0.5 Ω = 7 A from the battery. This is beyond the capability of the battery and therefore is virtually asking for trouble. If you were using a 2000 mAh IMR 18650 battery – with an amp limit of 10 A – you’d still be in the safe zone, which underlines the benefits of a larger battery for anybody interested in sub-ohm vaping.

    Using Ohm’s law and the information given on the maximum continuous discharge rating for your battery, you can ensure you stay safe when you’re vaping. The best advice, in terms of safety, is to only use coils with a minimum resistance of around 0.8 to 1 Ω, and if you’re vaping on low resistance, ensure you have a capable battery.

    This minimum resistance isn’t a definitive rule, strictly speaking (if you’ve done the math and you know you won’t be overworking your battery), but it reduces the possibility of problems significantly, and you’ll still get amazing performance from your atomizer. If you’re doing the calculations yourself to ensure your battery can cope, be wary of approaching the limit. You’re still affecting the overall lifespan of the battery if you run it close to its maximum output current, so it’s better to leave some wiggle room.
    Jack Sprat likes this.
  3. CentiZen

    CentiZen Evil Genius in Training Accessory Maker

    America's Hat
    A battery safety thread is something that FC desperately needs. On multiple occasions I've sat down and tried to write a general overview of battery safety as it applies to vaporizers, but never been able to make it too far because it always gets too long winded, too technical and would leave readers more confused than they were before they read them. I think that a text based approach is going to be missed by most readers, since most don't have the time or attention spans to parse and internalize all this information.

    These however, are great videos to watch to learn about batteries and battery safety. They cover pretty much all of the bases, and give you the base knowledge you need to understand the lingo and material that is being discussed in the threads. They don't cover everything though, and they assume a basic knowledge of electrical theory; but your good if you know ohms law.

    Click to play YouTube Video

    Click to play YouTube Video

    Click to play YouTube Video
    °k, RUDE BOY and mudshark like this.
  4. CrimsonKing

    CrimsonKing The Destroyer Of Worlds

    I would agree especially with all of these pen vapes coming out its only a matter of time until people start moving to the mech mods like the ecig vapers did and start popping batteries and exploding devices. I've been involved in the ecig world pretty extensively since they were introduced in the US (have gone though this) and have pretty extensive knowledge of what batteries are safest and best to use in what situation. Maybe a better way to go about it would to make a list of all devices with user replaceable batteries and then list the appropriate "safe" choice battery instead of a long winded post about safety etc? The biggest culprit of batteries failing especially lion ones is faulty / cheap crappy chargers, don't skimp on something you are going to use everyday and might burn down your house while you sleep if it's a POS.

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