Nice schematic and yes I have a voltage meter. But, while I have experience using these boards, I have no desire to become an electronics engineer and I'm not going to start poking around on the PCB. Dev boards like this should work on delivery for the market they are intended. I won't even begin on the many other issues I encountered 'Getting Started' with Onion. I will say that they have a long way to go before this is a 'stable' platform like the Pi or similar products. Still holding out.......
Waiting for some advice or RTV authorization for the Arduino Dock from the Onion team.
It might be possible, if the cell phone charger provides 5v. The standard iPhone brick does not provide enough to power mine, but I am using a BlackBerry one I had sitting around. I am also a fan of the Anker charging hubs, I have a few of those around as well, so I can charge multiple USB devices (GoPros, helmet cam, phone, tablet) at once. that works as well.
Check the power output to verify it is pushing enough.