A USB Battery Charging port can ship 1.5 A of present at 5 V. My iPhone 8 for example got here with a 1 A charger, so I am unable to assume that it will use greater than that from a USB A socket (it will possibly nevertheless use USB Energy Supply with a USB C cable).
Do any iPhones make the most of the upper present from a USB Battery Charging port?
Wikipedia has this to say about USB Battery Charging:
The charging system identifies a charging port by non-data signaling on the D+ and D− terminals. A devoted charging port locations a resistance not exceeding 200 Ω throughout the D+ and D− terminals.
Per the bottom specification, any system connected to an ordinary downstream port (SDP) should initially be a low-power system, with high-power mode contingent on later USB configuration by the host. Charging ports, nevertheless, can instantly provide between 0.5 and 1.5 A of present. The charging port should not apply present limiting under 0.5 A, and should not shut down under 1.5 A or earlier than the voltage drops to 2 V.
Edit
So, if a tool attracts greater than 1.5 A of present from a USB A port then — to me — that means that the system just isn’t in spec as regards to USB Battery Charging which, in accordance with the above quote, can ship a most of 1.5 A. My conclusion could be that in that individual occasion the system is utilizing another scheme of figuring out how a lot present to attract. That does not preclude the existence of assist for BC as properly, naturally.
I took an curiosity in USB charging just lately whereas repairing a USB An influence financial institution, and began questioning whether or not this BC customary is definitely being utilized by units. Since I’ve an iPhone I assumed it might be a great candidate to ask about.
Whereas I get the impression that my cellphone does make the most of greater present, it’s purely anecdotal and that additionally does not preclude the likelihood that it is utilizing some proprietary methodology.