ok so I drove my car today no problems. Came home like usual. Then I was leaving to go to the store and when i tried starting it it behaved like the battery was dead just trying to crank. Weird part is that after i tried starting it the lights on the dash stayd on even when i took out the key and opened the door.

But then I pulled up my girls 525i and tried jumping it. No luck. It cranked but then clicked. tried it for 10 minutes no luck. Keep in mind it was raining all day so i dont know if water got somewhere or what but its a crappy situation since i cant even look at it now since its pouring outside

 

Not sure what year you have. Have a look in the trunk in the foam tray the rests in the spare tire. There are a number of electronic modules there that are infamous for getting wet and ruining your day.

 

year and model always helps with these kinds of posts.