Found Extra Crank Battery Cable

[Brianrzr]

Not being a contortionist, in the 4 years I’ve owned my boat, I’ve never disconnected my batteries. For winter, I put a tender on each one and call it good. I removed my crank battery today, for better access to my rudder. I found a single #4 black cable that doesn’t look like it’s ever been connected since I’ve had it. It is a single #4 inside a loom with two tan fused lines, they run up along the rub rail to the starboard side. They are NOT the cables coming from the house battery. Everything has always worked, any idea what it may be for? I assume it would be negative since it’s black, am I correct? It may be a little hard to see, but it is in the photo. Any insight would be appreciated. 6EB49804-0054-4E8D-B05D-AA8A49C45BD7.jpg

[lee]

Brown and white wire should be for the automatic bilge pump constant power supply.

[boatwakes]

And the #4 black is a negative cable which most likely needs to be attached to the negative terminal of the battery at the battery.

[Brianrzr]

Thanks for the help guys!