The battery isnt getting its charge during the week? Ive had the same, my car doesnt go anywhere during the winter apart from in and out of the garage. My battery is about 3 months old and has gone flat already. Mines understandable, as it goes no where, sit in the garage, with the alarm on and nout charging it get a trickle charger, leave it on during the week and a fully working battery for the weekend