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Battery Safety in Devices by Nick Morrissey

by Jason Holloway August 30, 2014

Battery Safety in Devices by Nick Morrissey

Melodramatic? We don't think so.

New Vapers and seasoned Vapers: If you are going to read anything about battery safety - this is the post to read!  Know your limits and stay within it!

Written by long time vaper/first time guest Redux blogger Nick Morrissey. Thanks Nick!


Are you vaping safely?

This question comes up a lot, and it functionally means two things: are you running within the specifications of your device, and are you using proper batteries? These go hand-in-hand, and is something everyone should consider when they vape, regardless of what device you're using or what resistance you're building at.

Every device has a specification for safe operation. A regulated device, from an eGo stick battery, to a DNA-based device, high end box mods and even mechs all have specifications that you need to be sure to check. For regulated devices, this means the amp limit of the board, and for mechanical mods, it means the maximum loads the switches can handle. Regulated devices typically have built in protection to only allow you to fire atomizers within a certain resistance range. Generally, people who vape above 1 ohm don't have much to worry about, as nearly all regulated devices above an entry-level eGo battery can handle a 1 ohm load with no issue. But why? Because of something everyone who vapes and builds atomizers should know: Ohm's Law. There are a few calculations every vaper should know.

P = power in watts
V = voltage
I = current in amps
R = resistance in ohms

The first calculates amperage based on voltage and resistance:
I = V / R
e.g. 20A = 6V / 0.3ohm

The second calculates amperage from watts and resistance:
I = square_root(P/R)
e.g. 3.873A = sqrt(15W/1ohm)

The third calculates wattage based on resistance and voltage:
P = V^2 / R or P = (V*V) / R
e.g. 120W = 6V^2 / 0.3ohm or 120W = 6V*6V / 0.3ohm

For the bulk of the entry level variable voltage/variable wattage (VV/VW) devices, the regulator isn't actually pushing the exact number you're requesting. Either it doesn't regulate well, or it is self-limiting the current. A device like the Vamo, the MVP2 or the Sigelei Zmax have low amp limits. Fortunately, the regulator inside will not deliver the setting you've requested if it goes outside of the amp limit of the board. It will fire what IS safe and there is no issue. A device such as the ProVari has a very good regulator, but is purely variable voltage. While this is a bit of a nuisance for new vapers, it actually eliminates a lot of the math involved to find out if you're running safely or not. The ProVari 2.5 has an amp limit of 3.5 amps. The board will not put out more than 3.5 amps, and if you attempt to pull more than that, it'll give an error code. DNA and SX-based boards have similar safeties built in as well.

However, there are other devices out there that are custom built using hardware not designed for vaping, but capable of doing what we want it to do. These are advanced pieces of hardware that no novice should ever use. These devices are typically based on regulators from Murata, GE, and TI. The OKR-T/10 is a 10A device, capable of delivering 50W, the OKL2-T/20 and Naos Raptor 20A are both 20A boards, capable of delivering up to 120W. The issue with devices like this is that there is no protection built in to prevent you from firing builds that are too low. All of the devices can fire from anywhere from 2.5-3.3 volts up to 6 volts. These are the limits considered safe by the electrical engineers who have designed the circuits, and the voltages are not arbitrary. Ohm's Law dictates that a device that is rated for 10A can fire a 0.5 ohm coil at 6 volts, which is a 10A draw and 50 watts output. A 20A device, similarly, can fire a 0.3 ohm coil at 6 volts for 120 watts output. Because of the lack of protection from going too low, you can easily go outside of the specifications for the device, and drawing more power than the regulator is designed for. While some can handle it, some cannot, and the regulator can fail. As such, these devices are not recommended for someone new to vaping.

Mechanical mods can sometimes be rated to specific resistances too. Some manufacturers use varying quality springs and varying quality magnets in their device. When handling large amounts of current (amps), springs can sometimes collapse, which is ultimately a failed switch. Some magnets can become demagnetized under high current as well. Fortunately, recognizing such a failure is quite easy, and fixing the failure involves replacing the defective part. However, there are mods that involve parts that can actually melt, especially around the 510 connection for your atomizer. If you run your mod too hot (very low resistance), these insulators can fail, and such a failure is typically catastrophic, such as a dead short.

This leads us to battery safety.

For the most part, vapers use a small selection of batteries. Typically these include 18650, 18500/18490, 18350 and 26650 batteries. To quickly break down what those numbers actually mean, 18 is the diameter of the battery in millimeters, 65 is the height in millimeters, and 0 represents a round battery. The most common are the 18650 and the 26650.

In the 18 series, there are two types of chemistry that you will encounter. ICR and IMR batteries. They're all of the Lithium-Ion family, but the negative electrode (the anode) of the battery is composed of different elements. In an ICR battery, the anode is made of cobalt oxide. An IMR battery uses manganese oxide in the anode. ICR batteries typically have high capacity but very low discharge rates (the amp limit), whereas IMR batteries have lower capacity (though it is catching up) and high discharge rates. IMR batteries are what are known as "safe chemistry" batteries. 26650 ICR batteries are not particularly common in the vape community.

Because ICR batteries are not considered "safe chemistry," they typically have a built-in protection circuit to prevent over discharging the battery. Essentially the circuit sits on top of the battery (but contained in the wrapper), and will detect if whatever device using the battery is attempting to draw more amps than the battery is rated for. The result is that they cannot handle high amp draw, and are often best suited for low power units. Unprotected ICR batteries can be incredibly dangerous. IMR batteries are all unprotected, but because the amp limits on them are so high, it is a lot easier to operate safely with them.

Aside from capacity and discharge rates, the batteries are fairly similar. Except in the way they vent. Battery venting occurs when a battery is stressed or pushed beyond it's limit, overheats and begins thermal runaway. Because lithium ion batteries can provide their own fuel for combustion, the chemistry becomes very important. An ICR battery can vent very easily, as the discharge rates are so low, making that protection circuit very valuable. When an ICR battery vents, it is typically very violent, involving explosions and fire. An ICR battery, typically, will vent with a pop and release of some fluids and gases, but generally not violent. This is why they are called "safe" or "safer" chemistry batteries. With either battery, it is always a result of thermal runaway, and the battery will become too hot to handle. Always keep your distance from a venting battery, because even though IMR batteries vent less violently, they do create a lot of pressure, and a sealed mod can act similarly to a bomb. This has happened in the past, though the likelihood of it being explosive is rare.

The single biggest reason a battery will vent is because the resistance is too low, causing your amp draw to be too high. The closer your resistance is to 0, the higher the amp draw. Dead shorts were mentioned earlier, which essentially the result of 0 or very nearly 0 resistance between the positive and negative terminals on your battery. Ohm's Law says that 0 resistance means infinity amp draw. As such, the battery will quickly enter thermal runaway.

IMR batteries typically have two ratings, one is the continuous rating, the other is the pulse rating. Some batteries don't accurately state which is which. Always ask your vendor, but make sure you check it out online too. The continuous rating is the rate that the battery can be safely discharged to empty at. The pulse rating of a battery varies from manufacturer to manufacturer, but typically means the maximum safe amp draw between 0-30 seconds. Safe vapers will never build outside of the continuous ratings. Some more extreme vapers will put their trust in the pulse rating. It isn't recommended to go beyond the continuous rating unless you're very experienced and are willing to accept the risk.

Common battery types and their limits:
Sony VTC4: 18650, 2100mAh, 30 amp continuous, 60 amp pulse. Green wrapper.
Sony VTC5: 18650, 2600mAh, 30 amp continuous, 60 amp pulse. Green wrapper. (Currently the best battery on the market, though heavily counterfeited)
LG LE2: 18650, 2500mAh, 2500mAh, 20 amp continous, 35 amp pulse. Red wrapper.
Efest Purple 30A: 18650, 2100mAh, 30 amp continuous, 60 amp pulse. Purple wrapper. (This is basically a slightly lower quality VTC4)
Efest Purple 35A: 18650, 2500mAh, 20 amp continuous, 35 amp pulse. Purple wrapper. (This battery is sneaky, the label only says 35A, but that is the pulse rating)
Panasonic CGR18650CH: 18650, 2250mAh, 10A continuous. Gray wrapper. (This battery is rare to find, Tesla has bought out most of the stock of these worldwide)
Panasonic NCR18650B: 18650, 3400mAh, 12A pulse (5-6 seconds). Green wrapper. (This is a very high capacity but low discharge battery, best used in regulated devices).
Orbtronic SX30: 18650, 2100mAh, 30A continuous. Black wrapper. (This is actually a Panasonic battery)
MNKE 26650H: 26650, 4000mAh, 20 amp continuous, 60 amp pulse. Orange wrapper.
Sony 26650: 26650, 2600mAh, 26 amp continuous, 52 amp pulse. Green wrapper.
Efest 26650: 26650, 3500mAh, 32 amp continuous, 64 amp pulse. Purple wrapper.
Efest 26650: 26650, 3000mAh, 15 amp continuous, 60 amp pulse. Red wrapper. (there is a good video of a guy blowing one of these up online, in a horribly unsafe manner)

If the label says ICR, TrustFire, UltraFire or doesn't really say anything identifiable, don't use it. The risk isn't worth it. There are many more available than what is listed, but these are the more common ones you'll see. Always do your research, and buy batteries for your purpose. If you'd like to just buy a battery and not think about the different amp limits available, the Sony VTC5 is the best battery available to the vape community right now.

So what does this all mean? Well, it means you need to understand what you're working with. If you are using a regulated device, find out what the amp limit of the device is. If it has a 5 amp limit, don't use a battery rated for under 5 amps. If it can draw 20 amps, use 20 amp or higher batteries. Some regulated boards, such as the DNA and SX lines, can actually do some checking on the batteries to make sure it's not going to stress them. If it is going to stress them beyond the limit, it won't put the batteries under the stress, either by not firing or not providing the requested power.

However, regulated mods aren't the concern here. Mechanical mods are. Because of the very nature of how the devices work, battery safety is the single most important thing to remember when using mechanicals, especially if you start going in to the sub-ohm ranges (anything lower than 1 ohm). We're fortunate in the vape world because lately vendors have nearly all stopped selling ICR-type batteries, and typically only sell high-drain IMRs. As such, most atomizers at 0.5 ohms or higher on a mechanical mod aren't dangerous any more.

So a quick baseline, because we're going to be doing some math. All lithium ion batteries are called 3.7 volt batteries, but that is actually a nominal voltage, across the whole style of battery (not a specific battery or even a brand). Lithium ion batteries can safely hold a charge up to 4.2 volts (and not much higher), and no lower than 2.5 volts. Over- or under-charging them can cause permanent damage, reducing the life of the battery. Over-charging has the added benefit of potentially venting. For the sake of a worst case, however, we're going to assume that all batteries are fresh off the charger and charged correctly.

A coil built at 0.5 ohms on a freshly charged battery is only going to pull 8.4 amps.
4.2 / 0.5 = 8.4. Approximately 35 watts.
As you can see from the list of common batteries, all of them can safely fire at 0.5 ohms and above.

However, most people who start to venture under 0.5 ohms are chasing a different type of vape. Either they're looking for a more warm vape, or they're attempting to significantly increase their vapor product, or both. As was mentioned before, the closer your resistance gets to 0, the more dangerous things become.

At 0.3 ohms, you've hit 14 amps at nearly 59 watts (4.2 / 0.3 = 14). This is starting to get in to hot territory, and you're starting to make your battery work hard.
At 0.2 ohms, you've hit 21 amps at 88 watts (4.2 / 0.2 = 21). You're now outside of the safe continuous rating of the LG 20A and Efest 35A battery. At 0.2 ohms, you want to be using either an Efest 30A, or preferably a battery from the Sony line. 26650 mods are, generally, fine here.
At 0.14 ohms, you're now at the maximum continuous rating for 30A batteries. 4.2 / 0.14 = 30. This is about 126 watts. Any resistance lower than this is territory reserved only for those who have accepted the risk that their battery could fail catastrophically.

So why use 4.2 as the "safe" voltage? Couldn't one argue that the 3.7volt nominal rating is the best to use, and build to that? No. Because, as was mentioned before, 3.7 is nominal across the style of battery, not the individual. Sony VTC5 batteries often level off around 3.8-3.9 volts, making that it's approximate nominal voltage. At 3.7 volts, to get approximately 30 amps, you need to built at 0.12 ohms. Of course, your battery needs to drop that low first, so you'll be vaping starting at 35 amps, which is now in the pulse rating of the battery. 4.2 volts is considered the best baseline because the battery is only going to lose voltage, therefore reducing the amount of amps that can be drawn during the charge cycle. This ensures you start safe and stay safe across the whole charge instead of just part of it.

With all of that said, there are some simple steps you can take to remain safe:
First, if your mod ever starts getting hot (not warm, but too hot to touch), stop firing it. Put it down and step back. The risk of venting the battery is not incredibly high, but give it a few minutes to rest and then check it out. If it has cooled down, take the battery out and consider not using it again. The mod is likely getting hot as a result of the battery starting to fail. Further use can result in cascading failure, resulting in venting. You'll know if this is happening, as it gets hot incredibly fast.
Second, if your switch starts to get warm or hot, stop firing. This is usually the result of a failure in the switch, usually a short or dirty contact. The battery will rarely fail, but further use can cause stress and reduce the life of the battery. Take your mod apart and clean it. If it continues happening, the switch may be faulty.
Third, at the very least, get an ohm meter or resistance checker (whatever you want to call it). While you may get to a point where you find a build that you really like and can guarantee it'll always be the same resistance, it should be checked. There are problems you might not see, such as a short (your resistance keeps fluctuating while on the meter). If you're building something new or with a new type of wire, you may get unexpected results. It is better to throw it on a low voltage meter where there is no damage to be done than it is to throw it straight on your mod and blowing a battery. To get best results, buy a multimeter and get accurate readings.
Fourth, always know the limits of your battery, and stay within them. This is the single most important thing any vaper can and should do. There are certainly people out there who go below 0.1 ohms, and generally they've done their research and, more importantly, have accepted the risk they're taking. They know the signs to look for. But unless you're actually cloud chasing seriously, there is very little reason to go below 0.2 ohms, both for comfort (high wattage vaping can be too hot for a lot of people) and for safety.

Stay safe. No one will care how awesome your atomizer is, how great your mod looks, or how massive your cloud is if you've hurt yourself. 

Written by Nick Morrissey - Calgary, August 2014

*Reposted June 26, 2015

Jason Holloway
Jason Holloway


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