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How the Dell Precision 7530 PC Supports USB Power Delivery Charging with the Dell 65W PD Power Bank With and Without AC Power

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The Dell Precision 7530 allows up to 90W charging in to its Thunderbolt 3 enabled Type-C ports using USB Power Delivery 2.0 technology. However when connected to the Dell 65W PD Power Bank, the PC did not seem to take advantage of the max 65W offered by the power bank. In fact we only observed charging at just nearly half of 65W as described below.

Note the Dell 65W PD Power Bank was released as the first power bank to offer 65W USB Power Delivery 3.0 based charging. We first connected the power bank by itself to the Dell Precision 7530 without connecting to any AC power source. After the PC has charged for a while, we then linked up the power bank to AC power through the Dell 130W USB Type-C AC Adapter that shipped with the Dell XPS 15 9575 (2-in-1).

To observe how charging went between the Dell Precision 7530 and Dell 65W PD Power Bank, we used the GRL-USB-PD-C2 Compliance Test Solution App to capture the USB Power Delivery communication. When first plugged in to the power bank by itself with no AC power source attached, the PC was seen to start off pulling a quick spike of about 1 amps current as the voltage began on a 5 volts rail. The current then immediately dropped close to zero resulting in almost no charging. After the voltage ramped up to a 20 volts rail, the PC again pulled a quick spike of current to briefly charge at around 62 watts (20 volts @ 3.1 amps) before dropping current back down to near zero. After almost no charging for close to a minute, we then connected the power bank to the Dell 130W USB Type-C AC Adapter for AC power. This then followed by a hard reset which again repeated the same cycle of quick current spikes along the 5V and 20V rails. The PC then eventually pulled higher current to stabilize out charging at around 35 watts (19.5 volts @ 1.8 amps). During charging the current mostly stayed below 2 amps which limits the power drawn to only about 35W. View more details here by downloading the trace captured by the Granite River Labs USB Power Delivery Compliance C2 Tester.

This shows that the Dell 65W PD Power Bank by itself was unable to properly charge the Dell Precision 7530 without connecting to AC power.  

Download the C2 software from Granite River Labs here to view the trace.

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