Really need to scan the car for the best answer. However, if it cuts out and shows a battery symbol the best place to start would be the charging system. Need to look at both your battery and alternator to see if A. your alternator is putting out enough charge to keep your battery topped up, should be around 14V. Also if your battery is still in a good enough condition to accept a charge.
A scan though, would be your best bet, as VAG cars can be somewhat temperamental.