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What Happens Over USB Power Delivery When Charging the Apple iPhone X with the Apple 29W USB-C Power Adapter

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USB Power Delivery technology makes it flexible for the latest Apple iPhone X to enjoy rapid charging with various chargers out there supporting USB Power Delivery. Here we find out if the iPhone can be used with the USB Power Delivery based Apple 29W USB-C Power Adapter that was made to supplement the Apple MacBook (Early 2015)

When first connected over a Apple USB-C to Lightning Cable with the Apple iPhone X, the Apple 29W USB-C Power Adapter starts displaying VBUS increasing to 5 volts while preparing to charge non USB Power Delivery Lightning based devices. This goes on to initiate USB Power Delivery communications as seen through the Granite River Labs GRL-USB-PD-A1 app. The Apple 29W USB-C Power Adapter begins to repeatedly advertise 12 watts (5 volts @ 2.4 amps) and 29.6 watts (14.8 volts @ 2 amps) to the 67% charged Apple iPhone X over USB Power Delivery.

We can see after a while the Apple iPhone X initially requests 12 watts (5 volts @ 2.4 amps) which the Apple charger then accepts.

In between negotiations we also observe several Vendor Defined Messages continuously being exchanged including Discover Identity, SVIDs, Discover and Enter Modes, and Unstructured VDM.

Only when the Vendor Defined Messages have finally completed does the Apple iPhone X eventually request the max 29.6 watts (14.8 volts @ 2 amps) available which the Apple 29W USB-C Power Adapter subsequently accepts.

Looking at the power graph, the Apple iPhone X only starts charging at 5.2 volts after the first 10 seconds over inconsistent current when the iPhone is switched on at 67% battery upon plugin. As Vendor Defined Messages are exchanged and 29.6 watts (14.8 volts @ 2 amps) is requested, the voltage goes up to 14.8 volts while the current drops down to about 0.6 amps. The current pulled later bounces between a 0.5-1.2 amps range at 14.8 volts.

While at most the Apple iPhone X only draws power at around 17.8 watts (14.8 volts @ 1.2 amps), it can still be charged by the Apple 29W USB-C Power Adapter using USB Power Delivery. Moreover this power is slightly higher than what we observed when tested with the Apple 87W USB-C Power Adapter in this review.

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