There was a thread on this recently. As I recall, most dealers will replace as a matter of course at service interval. Shouldn't be a problem. I think when the battery is dead, the back up for ignition is to hold near the sweet spot on the steering column. It starts the car, but does not charge the non-rechargeable battery.
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2013 F10 550i | 6 Speed Manual | M Sport Package | Carbon Black | Oyster & Black Nappa | Dynamic Handling w/Dynamic Damper Control | Executive Package (Comfort Access - Soft Close - HUD) | B&O Sound | Luxury Seating & Heated Seats
(retired: 2002 E39 540i | 6 Speed Manual)
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