Jon, was this on your 640i?
If so, the battery is detective or failing, or it wasn't charged properly before you left it. No way a new car should do that.
I often don't run mine for 2 or 3 weeks, even in winter parked outside, never an issue.
Sure a charger is fine for a winter layover, but no need for a couple of weeks or so.
E63 AMG here at last!