When I had the minor backfire issue, the dealership tried pinning it on my short trips (err when was 25kms one way short?). Whatever I said.
They recommended a 450 dollar BMW Trickle Charger.
Thanks to this forum site, I got the CTEK 3300 from crappy tire for 49.99 on sale.
Batteries do only last 3-5 years, especially in the cold Canadian north.
Vancouver shouldn't be bad, but go pick up a CTEK when it's on sale and maintain the battery and then you'll be a okay.
2011 335i X Drive Special Edition-Jerez Black
35% Tint All Around / 3M Rockguard / Weathertech/ PPK2 / 18&12mm Spacers/Lux H8 V3