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Apple 12.9-inch iPad Pro Not Charging Fine on Dead Battery with the Dual Role Power Android Based Samsung Galaxy S9+ Over USB Power Delivery

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One of the nice things that came with the Samsung Galaxy S9+ is the dual-role power capabilities that can be used to lend a quick recharge to other compatible phones and tablets when there's just no access to AC power output. The Android based Samsung phone not only can act as a power bank and charging other mobile devices but also allows to be charged itself.

Using USB Power Delivery fast charging technology, let's see how the Samsung Galaxy S9+ supplies power to the Apple 12.9-inch iPad Pro when connected over the Apple USB-C to Lightning Cable. Given the Apple iPhone and iPad Pro's that support USB Power Delivery can only consume and not supply power, the Samsung Galaxy S9+ will be acting as a power bank to the Apple 12.9-inch iPad Pro, while consuming the phone's own battery charge to support charging the iPad Pro. With that you need to first make sure there's enough battery charge left on the Samsung Galaxy S9+ to last through entire charging. Also since the iPad Pro automatically just supports charging in when connected, you should select 'Charge connected device' from the Samsung phone's USB charging options.

However when using the Samsung Galaxy S9+ at 44% battery level to charge the Apple 12.9-inch iPad Pro from 0% dead battery, charging unfortunately didn't seem to work well over USB Power Delivery. We only observed charging over the first 12.5 minutes, after which charging stopped altogether.

When initially connected to the 44% charged Samsung Galaxy S9+, the Apple 12.9-inch iPad Pro was seen to start pulling only about 2.6 watts with its battery fully drained. As it reached 12 minutes of steady state charging, there was a quick bounce of voltage and current before the iPad Pro suddenly stopped pulling current to terminate charging with the Samsung phone. While the iPad Pro was still able to get around 2.6 watts during initial charging, charging was very slow due to the big battery on the iPad Pro. Click here to download the trace captured by the GRL-A1 power analyzer to see more details.

With a 5% charged battery on the Apple 12.9-inch iPad Pro, we reconnected it to the Samsung Galaxy S9+ at 45% battery level. This time around charging seemed to work fine over USB Power Delivery where the Samsung phone supplied around 5 watts power to the iPad Pro (which also results in slow charging for the iPad Pro given its big battery). We could also see that the iPad Pro has completely used up the Samsung phone's battery after about 48 minutes of charging. For more details, download the trace captured by the GRL-A1 power analyzer here.     

Here we have seen that the Apple 12.9-inch iPad Pro needs to have some battery charge to be able to work properly with the Samsung Galaxy S9+ rather than 0% dead battery state on the iPad Pro. Although charging will be much slower compared to using the Apple 12W power adapter, you can still use the Samsung Galaxy S9+ as alternative power source for the Apple 12.9-inch iPad Pro but just make sure the iPad Pro's battery is not well depleted for this case.

Download the A1 software from Granite River Labs here to view the traces.

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