I am running a Raspberry Pi 3A+ in my car as a DIY Android Auto head unit (using Crankshaft).
In order to not have the RPi immediately shutdown when you remove the key from the ignition (or have it reboot when you start the engine), I am powering the RPi directly from the car's battery. Using the ignition state, the RPi is booted and shutdown gracefully (after some time-out).
In other words, the RPi's 5V input is always powered. The RPi is just shut down when the ignition is off.
Well, the problem now is that the RPi keeps powering the USB port when it's shut down, which means the entire system still draws about 0.190 A (at 12V, so ~2.3 W). That is too much to run 24/7 because of the risk of sucking the car battery dry when left for multiple days.
Is there any way to get the RPi to cut the power to the USB port when halted, or is it hard-wired to the 5V line? I found some info for the
B models, but nothing for the 3A+.
Is this not possible on the 3A+?