Smartphone charger - why do they die so quickly?

Question

Electronics

At home, I went through a lot of usb chargers, from original to non-original.
So - they all give out 5 volts of voltage, then they practically do not give current:
For example, HTC, Samsung, Asus died from those tested. They were 2.1 amps and 1.5 for Samsung.
They were checked by connecting a switched off smartphone-wire-ammeter-charger.
All branded chargers gave out a current of no more than 0.15A. (i.e. charging a smartphone could take up to 15 hours)
I accidentally came across a Chinese non-name (a small one) - I check - the current is 0.55A (already more fun)
So here are the questions:
1. Why are chargers supplied with phones for 1.5 or 2 amperes if the maximum charge current is still no more than 0.75 A?
2. What breaks in branded chargers, that they give voltage, but do not give current?
3. Is it possible to charge a smartphone battery directly using the frog method, for example, with a charging output current of up to 2A and a voltage of 4.2V. Will the battery explode from overcharging, because of the three contacts of the battery, I use only two + and -? Or is it better to use a charge controller, for example, from a former bank for one bank?
4. How to really choose a good charger that will last a long time and will give out an honest current?

Answer 1

connecting a switched off smartphone-wire-ammeter-charger

Well, what the hell is this? How will the full charging potential be shown? What makes you think that the switched off phone should suck current out of charging?
Test for a resistive load, and even better for a normal dummy load. Then we can talk about the charger.
What test, such and results.
The charge current is determined by the phone's charge controller. In general, a slow charge is more useful for the battery, it will live longer.
If you need a quick charge, then take a phone that supports quick charge and charge it. They know how to turn up the pressure and pour good currents into the phone. Well, use a normal cable, not 3 hairs.

Answer 2

samsung and asus fire up the office

Answer 3

1. At maximum current, the smart is charged somewhere up to 50% of the battery charge. If you put on charging at 80% of the charge of the smart, the current will be low.
3. The purpose of the 3rd output in different batteries is different (google). The battery will not explode, because. above 4.2v it will not charge in this case. But you need to limit the charge current with a resistor, otherwise the charger will go into protection. But it is correct to charge Li-Ion / Li-Pol using the CC / CV method. First with direct current, then with direct voltage. This should be done by the charge controller, which is present in the PowerBank board.