please help. I have a 2000 Audi A8. The battery is dead,the battery is in the trunk but I can't open the trunk to charge it because the key won't work again due to dead battery. Supposedly you can't charge under hood.

 

Will the trunk not open by physically putting the key in the lock button located on the rear of the trunk lid? Insert the key, turn, and push the button in. You should be able to mechanically unlock it that way.

Also you can put voltage on the electrical system by using one of the cigarette lighter sockets.

 

No it doesn't work. It goes in and turns but nothing at all happens. This happened once before in the winter and I thought maybe the lock was frozen or something but that wasn't the case. I had it towed and had the shop jump it and do brakes. It's been almost a year so when I called the shop to find out what they did they claimed they couldn't remember.
I'm not sure what you mean about the voltage on the electrical system. You mean some kind of reverse charge...?

 

Never mind. I googled what you said. I'll try that. Thanx. Although I still want to understand why I can't open my trunk.

 

Advance Auto, AutoZone, and those type places have a battery module they'll use to connect to your car using a cigarette lighter socket to keep power on the electronics while swapping out the battery. That way any radio codes and such will not be lost during the swap.

My trunk lock on the back of my 03 A8 (D2 just like yours) doesn't turn either with the key. It's probably gunked up with dirt and needs to be cleaned. But if the car is unlocked (all doors) with the key, or the switch inside the door, all you need to do is press in on the button on the trunk and it will open. Apparently your drivers side door is the only thing that has been unlocked. And without power the rest won't open anyway.

Here's an adapter like I'm referring to. Cigarette Lighter Plug to Powerpole Connector 18 in. Adapter Cable [CGPP-18] - $12.99
You can connect another 12volt car battery to it to get power on the car to unlock the trunk. The power should feed back through the electrics just like a battery is connected like normal. Just don't try to crank the car with it.. LOL BZzzzzzzt.. I don't even think you'll have to turn the key on in the ignition switch to get the trunk button on the key fob or the door jamb to unlock the trunk. Once you've got it open, disconnect the temp battery and install the new one. You can even use the new battery for the temp to save having to hunt up another one.