2003 bmw 330i - battery ok. weather fifteen degrees

Hello, Sounds like the battery is not "OK" after all. I suggest a proper battery load test to see if it can handle the load as needed -- a full level of available cold cranking amps at 0 degrees Fahrenheit as rated and required.

Batteries typically last around 4-5 years so at 7 years you need a battery no matter what. Alex