Originally Posted by 1fastdoc
I hear several people saying that using a battery tender makes a difference but I don't see how. I assume you mean driveability.
I have an '11 M3 with a little over 8k miles on it. I drive 1.6 miles to work. 2.9 miles to the gym and then 1 mile back home. This is 5 days/week plus a few miles on the weekends.
So far it still starts fine, the lights are bright, the stereo is loud, the heated seats keep my ass warm, etc.
With prior cars when the battery goes bad it won't start. What's different with the M3?
I have experienced a dying battery firsthand on my Mom's 2010 528xi. Everything is fine and then you start to see the signs. I have discussed with my SA and with Mike Miller (Roundel Tech Writer) who lives nearby. Mom's driving profile didn't effectively charge the battery. In time you will probably have issues based on your driving profile. My SA replaced the battery (after it had died and left her stranded twice) and Mike Miller suggested a Battery Tender. I have used it since without further issues.
OP, good luck. I use the under the hood connection and it is very quick but I understand your need for keeping a low profile.