The speed your phone charges is based on the power used to charge the phone. The higher the power, the quicker your phone charges.
The Power (in Watts) your phone charges with is based on the charging Voltage (Volts) x Current (Amps), [P = VI].
Samsung’s Adaptive Fast Charge relies on increasing the Voltage from the ‘typical’ 5V to 9V and thereby increasing the power your phone can be charged with.
Three examples of charging a Samsung Galaxy S9+ are shown below, with the charging Voltage, Current and Power shown. The measurements were taken with a USB digital tester and are approximate.
Charging with a USB port on a computer:
Charging power = 1.76 W
The charging current is limited by the current the USB port can supply (0.5 Amps). This has a theoretical maximum of 2.5 Watts of charging power (5V x 0.5A = 2.5 Watts).
Charging with an adapter, with Fast cable charging turned off
Charging power = 9.08 W
Charging with a Samsung Adaptive Fast charging adaptor (Australian model) and cable – but Fast cable charging is turned off (in Settings → Battery → Advanced).
The power adapter supplies a maximum of 2 Amps at 5 Volts (you can read this information on the side of your adapter). This has a theoretical maximum of 10 Watts of charging power (5V x 2A = 10 Watts).
Note: ‘Typical’ wall adapters range from supplying 0.5 Amps to 2 Amps at 5 Volts (they do not support higher voltages). A typical adapter that can supply 2 Amps at 5 Volts should provide similar charging power and time.
Charging with an adapter, with Fast cable charging turned on
Charging power = 13.04 W
The adapter supplies a maximum of 1.67 Amps at 9 Volts (you can read this information on the side of your adapter). This has a theoretical maximum of 15 Watts of charging power (9V x 1.67A = 15 Watts).
Note: Samsung Adaptive fast charging changes the current and voltage during charging and this will impact the charge time.
Samsung Adaptive fast charging requires an Adaptive fast charging adapter and compatible cable (e.g. that can deliver up to 1.67 Amp at 9 Volts) and a compatible phone. This can provide faster charging of your phone as higher power can be used while charging when compared to a ‘typical’ adapter.