My 2004, 36,000 miles, Audi A6 has had starting problems recently. Couple of jump starts and all seemed fine. Won't start again today - battery shows 100% on screen in dash board. Noticed when starting yesterday three ticks when turning the key before the engine started. Today the ticks came after the engine turned over but wouldn't start. Will it simply be the battery needing replaced - or something else????

 

Get a LOAD Test run on the battery and you should know for sure if a new battery is needed or not. Advanced Auto and many chain Auto parts stores can do that for you for free.

Good Luck...

 

Since your A6 is a 2004, possibly first sold in 2003, it is very likely that your battery is the original and needs to be replaced.
What you see on your dashboard is not the state of the battery but rather the charging system; that is good news because it is much easier and cheaper to replace a battery than it is to replace an alternator.
Have the battery checked for the heck of it but be prepared to spend over $100 for a new unit. Peace of mind comes at a price!