Fuse box wire

[Flounderguy]

2009 335I. I am new to the forum. I am having a ‘no power’ problem. When I put the key in, nothing lights up. No power to start.

I had the battery hooked up to a charger in the engine bay. I bumped the the charger cables. They touched. No power since. Battery is good. B+ cable in the trunk is getting power. IBS is ok. I dropped the fuse box and the B+ cable is getting power to the fuse box, looks clean. So, two questions:

What did I blow?

I’m putting the fuse box back in and found a single red wire with a silver metal connector, about the size of the end of a USB cable. Any idea what it is and where it goes?

[Flounderguy]

Admin, can you move this to 3rd gen. Thanks.