I see a lot of confusion around this topic, and I wanted to lay it out as plainly and simply as I could for beginners. This isn’t going to cover the debate of internal/external charging for removable cell devices. For safety’s sake, let’s just say, charge those externally wherever possible.

How does USB Charging work?

USB charging and data transfer run on a number of different “Specifications”. There is USB 1.0, USB 2.0, USB 3.0 and USB 3.1. Each of these has it’s own details and specs, but generally speaking, USB charging follows ohms law (as does yknow…all electricity), and all of these specs are designed to run at 5 volts.

The host (The device being charged, E-Cig/Box Mod Etc), has a small chip attached to the USB port, that regulates what comes in. This small chip inside the device basically says to the charger “I want X amounts of amps please”, and the charger delivers what it can. The amount of volts that this calculation is based on, is 100% of the time 5V when it comes to ecigs. These all run on 5V, as do 90% of consumer USB electronics.

The amps can vary by device to device and how quickly the battery inside can charge safely, but these are decided by a small resistor inside the charging board. This resistor follows ohms law (much in the way a coil does in an ecig), and dictates how many amps are being asked for, from the charger. So the device is designed to charge at 1 amp, it assumes the charger is 5 volts, so they stick in a resistor of 5 ohms, which equals out to 1 amp of power, according to ohms law. Boom, job is done, easy peasy.

This means, that no matter how many amps the charger can supply, 2 amps, 5 amps, 10 amps, 500 amps. The Device will only ever “pull” 1 amp of power. Amps are “pulled” from the charger, they are not pushed from the charger. If you have a USB charger that can provide more amps than the device charges at, this doesn’t matter, as the device will still only request what it needs.

So why do e-cigs “explode” whilst charging? Why have I heard to only use certain chargers?
There can be a lot of reasons for this. To name the most common few:

Low quality, poorly built chargers, that fluctuate above 5V. This causes the charger to pull more than the amps it is designed to handle, and this can short-circuit things, in extreme cases, even overriding over-charge protections. Always use a high-quality charger. Not the cheapest, lowest common denominator Chinese charger bought on Amazon with 3 reviews. You would not believe how poorly and unsafely wired some of these are inside. A millimeter of cheap slave labor level soldering away from a hard-short. Absolute deathtraps.

Low quality, poorly constructed USB cables. A thin USB cable that is designed only for data transfer, charging at 2A for example, puts a lot of strain on the charging port, small choke points, and thin gauge wires inside can overheat, short out against other wires inside the cable, and cause a short at the micro USB port, causing anything from small scorch marks, up to an overcharge or hard short on the battery terminals, leading to thermal runaway and venting of the battery. Always use a nice thick, well-made USB cable.

Certain mobile phone chargers that feature “Quick Charge” technology. Most notably, Samsung and HTC. In an effort to bypass the slow charging of the agreed upon universal USB standards and make their phones charge quicker, certain phone manufacturers developed their own usb “Standard”, usually called Quick-Charge, or Qualcomm Quick Charge. These phone chargers are meant to be used EXCLUSIVELY with their specific charger, as it can switch between 5V, and anything as high as 9 or even 15 volts. This is the main cause of issues that we see with charging e-cigs. These phone chargers are not meant to be used with ANYTHING other than the mobile phone they came with, especially nothing as sometimes rudimentary and lacking in protection, as some low-end e-cigs can be. Always make sure that the charger you are using says 5V output, and nothing else.

To demonstrate: Using the same example from earlier, let’s say a device’s battery is designed to charge at 1 amp. To do this, they use a 5-ohm resistor in the charging circuitry, this means that is connected to a 5v power supply, it will pull according to good old ohms law, a perfect 1 Amp. HOWEVER. Let’s say you hook it up to a charger that can switch up to 9v. Now, that equation changes and the charging circuit is pulling 1.8 amps. This is nearly double what it was designed to accept…If the charger switches up to 15 volts, that’s now delivering 3 amps, triple what it was designed for! You can see why that could cause issues.

4) Dirty charging ports on an end part of the connection. Any small bits of dirt or dust can potentially block up the rails on the usb port that carry power, leaving the power to flow through a very small surface area, causing excess heat or in the worst scenarios, short-circuiting. All of which can lead to a potential incident. Always make sure USB ports on the cables, device and charger, are free from dust and debris.

So, what do I do to keep myself safe?

Use a thick charging cable. The thicker and beefier the better.

Use a charging port on a computer/laptop/xbox or any other electronic device. These are far more heavily regulated and safe than dedicated USB plugs, as they have to protect both sides; what gets plugged in, and themselves. The downside is, these are likely to be the slowest method of charging.

MAKE SURE YOUR PLUG SAYS 5v, and 5v only. If it makes any mention of any other output voltage such as 9v/13v etc, then DON’T use that charger with an ecig. And you really shouldn’t be using it with anything other than the phone/device it came with. The documentation that came with your phone/device will also tell you that, but who reads that?

Keep an eye out for any dust/dirt in any of the ports, and if you find any, try and tap it out, or brush it out with an anti-static brush.

Content provided courtesy of cheesebanana on reddit. View the original post here.