If the battery's been fully charged but there is no life even when hammering on the starter, it's probably the internal relay inside the starter solenoid that's the problem. I dont think you can buy the solenoid separate, so you may have to replace the starter for a new/used one.

__________________
If you have a 5 cylinder, you don't need a stereo.

1999 Audi A6 quattro
1990 Volkswagen Golf CL Syncro
1987 Audi Coupe quattro