I have the following accessories connected to my car
1) dashcam connected on piggy back to 15amp fuse F15 for power socket,
2) usb LED floor lighting connected in power socket,
3) usb pen drive with mp3 music connected to front USB socket.
4) USB lead for mobile phone connected in usb socket
I know that when I turn car off by pressing stop switch that they all turn off after a short time starting with dashcam in a few seconds and a longer delay for pen drive and then LED lights.
Just wanted to confirm that it is ok to leave USB accessories plugged in as car turns off the power socket power to save the 12v battery.
I ask as I've had issues with my 12v battery not having enough power to engage traction battery this week. I may have a duff 12v as car is only 1 month old and don't know if dealer properly charged it as only my second granny charge since I got it on 23rd December. It could also be that in lockdown I've not been doing many journeys in it.
I can also confirm for others that the 12v battery gets charged up whilst charging on a granny charger and I assume a home 7kw charger.