I had a slight hesitation on start up, but it never failed to start. I just wanted to do it at a time and place I controlled. Also, travelling in -20C weather, a vehicle that doesn't start can be a significant risk. We were stopped in the Rockies for avalanche control, and while we have space blankets and emergency supplies with us when in those conditions, it wasn't worth the risk.

No need to go to a dealer. BMW doesn't make batteries. Just make sure it is the correct size, equal or better in CCA and reserve capacity, and with the proper vent.

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2007 X3 3.0si, 6 MT, Premium, White

Retired:
2008 535i, 6 MT, M Sport, Premium, Space Grey
2003 X5 3.0 Steptronic, Premium, Titanium Silver
2002 325xi 5 MT, Steel Grey
2004 Z4 3.0 Premium, Sport, SMG, Maldives Blue