a3 tdi multiple problems!! (doing my head in now please help)

Can anyone confirm the correct size battery an A3 can hold? I have just seen 2 different Varta batteries and apparently both fit the A3 but they are different in length and power output:

Varta Silver Dynamic 585 200 080 3162 : 85Ah|800A - 317L x 175W x 175H (mm)
VARTA SILVER dynamic 577 400 078 3162 : 77Ah|780A - 278L x 175W x 190H (mm)

Which is the right one for Our A3?
 
Just been and measured my (original) battery. 2006 Sportback

280 x 170 x 180 H Varta - Audi part no. 1J0 915 105 AF

You need the second one you mentioned as the first will not physically fit as it's too long for the box !
 
Ok so I sorted the starting problem with a nee battery so thankyou so much for your help but iv still got the juddering :( sometimes switching the A/C on makes it stop and sometimes it doesn't :s any more suggestions please?
 
get your timing checked front cam can be dun on a laptop but the rear cam has to be manualy checked.

if you dip clutch does judder stop

vw did an ecu flash update for the judder probelm if you havr tried every think else but audi dont do it.
 
Thanks for your reply, no the juddering doesn't stop with the clutch pressed, how would I get the ecu update from? Does anyone know any good garages near birmingham I could take it to that won't rip me off to get it sorted?
Thanks