At some point in the span of owning my R53, the sunroof started leaking into the cabin during heavy rains, leading to moisture making it's way to the rear battery box. I didn't notice it until a mildew smell started, and by that time the leads and fuse connections under the square plastic cover on the side of the inset area were pretty rusted. Not sure how long water was making it's way into the box, but the connections are rusted to the point that I'm worried about their reliability. I've been driving it without issues so far, but assume it will haunt me if left alone.

Has anyone replaced the positive connection to the battery and fuse? I've installed new battery connections on cars with simpler setups, but the Mini's has me a little stumped. I see that a new positive cable is $300+.

 

Same issue with my battery except the leak was from the tailgate handle gasket. My battery box had 5 inches of water in it or so. My fuse box down there is also pretty badly rusted. It has been 2-3 years since I noticed it and I intend to replace that whole fuse box but I'm not going to replace the entire positive cable. My plan is to get an appropriate length 4-gauge cable, cut out the rusted section and splice the new section in.

 

Allmag auto in Tampa - I’ve had good luck with used parts from them.