If I set "fast charge" on my S21 ultra and connect my Samsung 45 watt USB PD charger, the device will indicate (confirmed by the Ampere apps) that it is charging in slow mode (charger plugged in). If I set "super fast charge" with the same charger, the phone shows "super fast charger" plugged in. On the other hand, if I plug the same charger into a S10 with "fast charge" activated, it does indicate "fast charger plugged in" (confirmed by Ampere). Does anyone have an explanation why the 45w does not activate fast charging but only slow or super fast charge depending on settings?
P.S .: A Samsung "Adaptive Fast Charge" charger does enable fast charging on the S21 Ultra.
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- S21 ultra charger
Galaxy S21 series supports the various charging methods such as AFC(Adaptive Fast Charging), QC 2.0(Quick Charge 2.0), and USB PD(Power Delivery) for wired charging, WPC(Qi) and PMA(Power Matters Alliance) for wireless charging. When using a charger, it is recommended to use an approved wired or wireless charger that guarantees the charging performance. Incompatible battery, charger, and cable can cause serious damage to your device, and charging may not work properly. Use only USB Type-C cable supplied with the device.
To use fast charging feature, you must use the approved battery charger that supports fast charging feature and fast charging feature must be activated.
For this, you can use a battery charger that supports AFC(Adaptive Fast Charging), PD(Power Delivery) 2.0 , or QC(Quick Charge) 2.0
In case of Samsung chargers that support Adaptive fast charging, Adaptive Fast Charging text with icon is marked and it supports output power 9V-1.67A(15W). For a charger that supports PD 2.0 or QC 2.0, you should also make sure that the charger to be used meets the specifications. If you use a charger that does not meet the standard specifications, it can operate only as a general charging or low speed charging. We do not guarantee the compatibility of third-party chargers.
Super fast charging:
To use the super fast charging feature, you must use the approved battery charger that supports super fast charging feature and the super fast charging feature must be activated.
For this, you can use a battery charger that supports PD(Power Delivery) 3.0 such as Samsung 25W charger or 45W PD(Power Delivery) charger. When you connect the device with PD 2.0 charger, device battery is only charged by fast charging. To activate the Super Fast charging feature, launch the Settings app, tap Battery and device care> Battery> More battery settings, and then tap the Super Fast charging switch to activate it. On Samsung chargers that support Super fast charging, Super Fast Charging text with icon is marked and it supports output power 9V-2.77A(25W), or 15V-3A(45W) or 20V-2.25A(45W).
In case of charger that supports Super fast charging, it's required to have USB-C type connector and support PD3.0 PPS 3.3V~11V/2.25A or higher. Also it should be the official USB certification product.
I have no idea, to be honest. I usually use only one type of Battery chargers, so I don't activate super fast charge at all. I'm pretty sure that it's not good for the battery to use different types of charging, even though sometimes, it must be really important to charge your phone asap. But in that case, I just take power banks with me.