I am away from home and did not bring my phone charger. Would I be able to charge it from the accessory outlet without actually turning on the car? I pressed the start button once and it has lit the outlet without turning on the car. I am just concerned that I may deplete my battery (non traction battery).
From your post I gather your phone needs a USB charger and also you have the cable for it. I would just pick up a USB charger and use that if you need more than an hour of charge.
FYI, I've found a DC plug with a USB port in it charges my phone much faster than must plugging the USB cable into the USB port.
We use the Prius v5 USB port to charge our smart phones 1 at a time. While driving we tried using a USB Y-splitter to charge 2 smart phones concurrently... however an ERR message popped up on the screen that read something like "power demand exceeded limit" and it immediately shut down the USB port. We asked the dealership about the max draw from the USB port. They didn't know even after sending the question directly to Toyota HQ. We suspect Toyota installed in our 2012 V5 a outdated USB 1.0 port eventhough USB 1.1 and 2.0 have been out for several years. In today Sunday adv's we noticed that computer notebooks now are using USB 3.0 ports. Our solution was to use the cigarette lighter outlet /USB adapter for 1 phone and the USB port for the 2nd phone. Of course our two smartphones are connected by Bluetooth signal. AND both USB and power port are disabled when the Prius is powered down/off.