Audi allroad ‘02

They should have check your voltage regulator

if they tested the alternator and the voltage checked out then the regulator was ok. If the alternator is any wher eover the 250,000km range then the brushes on the regulator will likely need replacing. easy fix. any ways if the battery died on its own that means your battery is no good or you have a short which is draining more battery then the alternator can handle for recharge. This would be something like a car stereo amp with out a battery capacitor. High power stereo systems draw more power then the car can handle for recharge so the battery dies even if your driving. **this is only an example ** and to answer the stall question yes the car will shut off after the battery is less then 11 volts Also have all your grounds checked it is possible they are corroding and causing an improer ground which reduces alternator voltage. one good place to check is the starter. i have had my wires rot right off before due to the salt here in canada.