my car has developed a strange problem. I think its just a duff battery that's brought on by the cold. I have a group a coil/loom that takes power directly from the battery. it has ran flat twice now and I have since charged it and its ok for a day or two. today I started the car, struck up straight away, left idling for 5-10 mins then it just cut out. went to start and the battery is dead again. is it possible that the coil/blowers are taking more power from the battery than the alternator is able to charge at idle speed (950rpm ish). or is it just a duff battery.