I have an old iPhone 4s that I use as a music player in the car. It is plugged into a cigar-lighter socket that is only powered when the ignition is on. The phone's battery life is not particularly good anymore, so after turning off the ignition, the phone, if left as is (powered on), will deplete its battery in a few hours. Next time I get into the car and turn it on, the phone will be completely dead and have to charge for 10-20 minutes before I can power it up and start playing music.
However, if I remember to power off the phone when I turn off the car, the phone battery will generally be good until the next time I turn on the car. When I turn it on, the phone will start receiving power again and automatically turn on.
Instead of having to remember to manually turn off the phone when I turn off the car, is there some way I can have the phone automatically power off when it is no longer receiving power? Ideally it would wait for 10-20 minutes before powering off (if I stop for gas or something), but immediate power-off would be OK too.
I have looked for settings and apps that could possibly do this, but so far haven't found anything.
FWIW I do also have a cigar-lighter socket that is always on, regardless of ignition state. I could possibly plug the phone in there instead, but I got wary of that - last winter my car battery was a bit weak and I left the phone plugged in like this for perhaps 3 or 4 days without starting the car, and it ran the car battery right down. I have a new car battery now, but I'd still rather avoid having this continuous drain on it.