1986 Audi 5000 Where is my battery

I guess if you haven't found it under the back seat by now, you sold the car! BTW, that little clear, vinyl hose is a vent hose that attaches to the correct battery for that car. It vents gas from the battery out of the car. If you use a sealed battery, it doesn't matter. And another BTW, that little electronic black thing on the floor next to the battery is the door lock actuator pump!

That's ok hellmonger. That's not a stupid question at all. All of us here became newbies and I'm still one. That's why I've been spending hours going around the Audi section to learn.