Aux power plug ?

The smartphone does not send any voltage back when the car is off. I was talking about the power bricks, the portable usb battery extenders that many people use when their phone battery depletes.

 

Thank goodness! Thanks for setting me straight!

 

Glad to report that my Jackery 500 does not have any backflow current from the cig lighter plug used to charge it. The Jackery is slow to charge from the cig. lighter at only 85 watts, but it is interesting that my gen2 has two independent circuits with that same 120 watt limit. I could actually charge two of the Jackery's independently and effectively cut my charge time in half. Of course, many Prius campers just connect an inverter direct to the battery or to an aux. battery connected to the battery with a solenoid that disconnects it from car when car is not powered on. Certainly, a second lead acid battery is a lot cheaper than a Jackery and can be charged by the car without any additional chargers. Found a video of a man who lived in the gen 2 Prius for 3 years with that second battery setup which testifies to the fact it works with no harm to car.