I haven't started up my 328 for about 6 weeks over Winter and was quite surprised to find the battery almost flat. I replaced the battery last September so I am certain there is no problem there. I didn't bother to use the battery shut off switch this time. What do you reckon is causing the battery to run down ? I have had other cars unused for longer than this in the past with no problem. The battery is already on charge so no big deal, but I am just curious.