Understanding quick charge(Qualcomm)

[BuMS]

I often hear Linus, ranting about how quick charge is bad for the battery.

He claims(As far as I can tell) the battery runs hot, from the increased voltage and the battery will die.

It properly will die, at some point...

 

So this made me wonder... Is the battery feed higher voltages?

When charging a RC Lipo, the voltage stays within the Lipo's spec(About 3.0-4.2v).

But you charge it faster by increasing the amps, not the voltage.

RC batteries(Lipo) can usually be charged at a 5C rate, and if phone lipos aren't lesser quality, they should be able to do 1C rate or more.

 

The C charge rate, is the multiplication factor, of the batteries capacity in Ah(Amp hours, and batteries are often labeled in mAh(milliAmpere hour))

So a 3000mAh battery is 3Ah, and at 5C rate, that would mean the battery can be charged with 15A(And 3A at 1C).

 

The good old USB spec is only supplying 500mA(0.5A) at 5V, and most off-the-shelf chargers can deliver 1-3A at 5V.

I did some testing on my LG V10, and the battery only receives the "Lipo spec" voltages(3.7-3.8V at about 25% charge), while connected to a quick charge charger.

On top of that, the batteries temperature stayed at about 35-40C.

That means the voltage is dropped by the phone, from the 5V(Or up to 12V with quick charge 3.0) to the batteries voltage(3.7-3.8V at about 25% charge in my case).

 

With a standard USB(0.5A at 5V) charge and the phone's battery at 3.7V, the phone can receive up to(In theory):

Output from the charger: 5V * 0.5A = 2.5W

Output from the phone to the battery: 2.5W / 3.7V = ~0.68A

 

And a normal 1A charger:

Output from the charger: 5V * 1.0A = 5W

Output to the battery: 5W / 3.7V = ~1.35A

 

Now lets take quick charge, at 9V and 1.0A:

Output from the charger: 9V * 1.0A(Can go higher) = 9W

Output to the battery: 9W / 3.7V = ~2.43A

 

The higher the Amps the hotter the wires get, so being able to stay at 1A, keeps the wires from melting.

And if the battery can sustain at least 1C charge rate, 2.43A is no problem for a 3.0Ah battery.

Of course, if the batteries can't handle 1C or higher, they can die/melt/fiery inferno...

 

So it all depends...

Have the manufactures used good batteries?

Try asking Samsung? ;-)