acirlam

I drove a saab 2002 9/3 2.2 litre diesel right hand drive , from the uk to Romania 2 years ago , where it's been till now. I've had a few problems that I've managed to fix . However, this morning was quite cold , last night was below freezing. The car started as normal , and was left to idle so the heater would defrost the windows and warm up the car. After about five minutes my wife noticed the windows were not defrosting , in fact the fan was no longer on the and the digital readout was very dim. She also thinks the car was not idling as normal , somehow weaker. She turned the engine off to re-start it , the battery was dead.
Last winter was very cold and we had no problems. Is the cold just a coincidence and somehow the alternator is not doing it's job?
I was 15 years in LA before moving here for a bit, where obviously we had no such problems. Any advice would be great.

boostpowered

bad batteries will show themselves in cold weather