[Galaxy Note 4 Q&A, Help & Troubleshooting] Chefproll:
Hello again ! ;)

After all cooled down a bit, here's some more information about that dreaded HIGH VOLTAGE fast charging uses which seemingly makes some of you wet your pants. :D

First, there's an experiment you can do yourself. You don't need to do - but it's quite impressive and gives you some proof of the things I say.

Get two 9 V batteries; the small rectangle ones we all know. Connect the positive contact of the first battery with the negative contact of the second. Thus you get an 18 volts DC power source.

Get a thin, isolated wire, short-circuit the open contacts with the wire. Wait.

Nothing special will happen, maybe the wire will get a little warm - and your batteries will eventually die.

(If you use a VERY thing wires, it might heat up.)

Now take a length of the same wire, do the same using your car's battery (12 – 13.8 V DC).

WARNING !

1) Take the battery out of the car, set it on solid ground with nothing combustible near !!! Do NOT try this with the battery still in the car !!!

2) Use pliers to connect the wire with the battery contacts !!!

3) Do that OUTDOORS !!!

Short-circuit the battery contacts using the pliers with the wire.

You don't need to wait. The cable will turn into a smoking, burning, white-hot thing in an instant.

Huh ? - We've got 18 V with just nothing happening, we've got just 12 V wreaking instant havoc and destruction !?

Amperage is the key !

Voltage alone does not cause the destruction, it's the amperage.

9 V batteries cannot provide sufficient amperes for killing the wire; 12 V car batteries do.

Short: High amperage kills wires, high voltage doesn't.

So back to our topic...

To fast charge our Note 4's battery, we need power, watts. But the tiny wires in the Note 4 can't withstand a high wattage; they would heat up like the wire connected to the 12 V car battery.

So Samsung uses a little trick, according to Ohm's law: W = V * A, W is watts, V is volts, A is amperes.

So we can achieve a high wattage by EITHER using a higher voltage OR a higher amperage.

Higher amperage does not work because it will kill the tiny wires in the Note.

So Samsung raised the voltage for carrying more watts from the power supply via the internal Note 4's cabling to the charging circuit.

That higher voltage gets transformed down to the normal charging voltage at the charging circuit.

Your battery is charged with the usual voltage, but with the benefits of a higher amperage.

That's all the magic: That higher voltage is used to carry more wattage to the charging circuit, but not beyond. Nothing else.

And that's why it does not harm your battery; charging voltage will not change - your battery just gets charged faster, always monitored by the charging circuit which will lower the charge accordingly if needed, so your battery will always be safe. That's why the "last mile" (charge from about 92 % to 100 %) takes more time to charge - because the charging circuit automatically lowers the charge to protect your battery.

So don't be afraid of that higher voltage; it never reaches your battery, it is just a means for transferring higher wattage via tiny wires.

Note: You ever wondered why Europeans use 230 V instead of 110 V ? - That's the reason. Being able to carry more watts over regular power lines without risking the wires heating up too much. It's not a means of destruction, it's the opposite.