Originally Posted by Mister Bally
remove the bottom cover below the engine and connect a nice battery charger or jump box to the big red wire on the alternator. Ground to the alternator case or engine block etc.
NEVER EVER try and start / power up the car by removing the bottom engine cover and clamp onto the red alternator wire.
The only correct and safe way to connect power to the A8 is via the battery +VE and the -VE charging Post in the trunk. This make sure the power it routed via the battery management controller.
The key is simply removed my pressing the little recessed button on the outer ring of the ignition barrel. This needs to be pressed with a very small screwdriver / tooth pick etc etc. When this is pressed, the key can be rotated and removed.
The trunk can now be opened from underneath the boot lip.
Now connect a jumper pack / battery charger to the +VE (red) of the BATTERY, and the -VE to the Large Metal charging post stuck out horizontally from the Battery Management Module.
This is the Correct way to perform this, and will ensure the car is projected from power spikes and surges.
The A8 is a little venerable to spikes and one of the first things to get wiped out is the ABS unit, so beware!