How to test phone charger with multimeter?

The article is about how to test phone charger with multimeter

Test the 5V/1A mobile phone charger with 5W power:

1, if your phone charger is nominally 5V/1A, then you can find a 5 ohm, 5W resistor as a load resistor. (R=U/I=5V/1A=5 ohms, the power must be equal to or greater than 5W, otherwise the resistance will be burned off. In addition, the resistance will be very hot during the test, be careful of burns.)

2. Test the USB terminal output voltage when the mobile phone charger is connected to this resistor. If the output voltage is lower than 4.7V, then your charger may be a copycat charger.

Test the 5.1V/2.1A mobile phone charger with 10W power (if you test the 2.4A/12W mobile phone charger, the resistance value will be smaller):

1, the value of the selected resistance is: R = U / I = 5.1V / 2.1A = 2.43 ohms, similar, we can find a 2.5 ohm resistor, the power should be more than 10W. You can find two 5 ohm resistors in parallel, or four 10 ohm resistors in parallel.

2. Test the USB terminal output voltage when the mobile phone charger is connected to this resistor. If the output voltage is lower than 4.7V, then your charger may be a cottage charger.