i was getting the same message, plus my comfort access wasn't working. i have an old ct charger in my basement. so i hooked it up at 2amps (2/10amp option) and charged it over night. the gauge was showing me 40% charge on the batt when i started, next morning was at around 90%. basically just plugged it under the hood. positive to the positive post and negative to a grounded bolt.
message went away for me. haven't seen it since the weather warmed up. i also agree that the battery seems sub-standard if it isn't holding a charge in cold weather... and like some other's i don't seem to have a long enough commute to charge it.
'13 F30 335xi • white/black • m-sport
'08 E93 335i • 6MT • white/red • fully loaded • 35% • m-technik • some other goodies...