Had a little problem with my wireless charging pad. The one I bought was rated for 10.5 to 14 volts which usually means it will work fine in a car.
Apparently that range is a hard number on mine, and the 14.15 volts the Cayenne charges at was too much for it, so my charger would shut down whenever the engine was running.
For a quick fix I made this little inline voltage dropper:
The two large diodes are NTE5812's and the the smaller one is a P6KE18 TVS. The NTE5812's each add a voltage drop of around 1 volt and are rated for 6 amps, which is much more than the charger will use. I selected these because I have a lot of them. Any normal silicon diode rated for a couple amps should work fine here.
The TVS will clamp larger voltage spikes and is optional, I just have a bunch on hand so I figured it wouldn't hurt. If you don't have any that's OK, the larger diodes are the ones actually fixing the problem. I wrapped the whole thing in heat shrink after testing it.