Everytime I do something on the car that the battery needs to been disconnected, all my setting on the HU is gone because the memory wire also is not getting power then.
Now I have thought about a little trick but want to check if someone see something I forgot to take into account.

The idea is to add a capacitor between the memory wire and ground and a diode in line with the memory wire before the capacitor. The diode is to stop current flowing back into the cars system from the capacitor. I have not yet calculated the size of the capacitor. A capacitor is maybe not going to work in which case maybe a very small battery in the place of the capacitor.

Is my idea going to work? maybe.

 

i forgot what its called but there is a little gizmo that you can plug into your cig lighter that has a 9v battery on it. It keeps your radio & clock settings.

 

In theory that should work.