Identifying wires @ batteries

[marchem]

Doing some detective work on the electrical system of our C310 (2000), tracking down what goes where before I do some rewiring (ala Maine Sail, Stu Jackson, and Jesse). Currently these are the wires on the two 4D batteries:
Hot side:
Battery 1 and 2:

• #1/0 to battery switch
• #4 to charger

Ground side:
Battery 1:

• #1/0 to engine block
• #1/0 to battery 2
• #4 to DC ground bus bar behind electric panel

Battery 2:

• #1/0 to battery 1
• #4 to charger
• #4 to ???

The mystery #4 black wire goes aft under the head sink, continues behind the shower shelf, and then disappears up towards the rail. I'm suspicious that it might go to the windlass, but why it takes such a round about route baffles me. I'm pretty certain it's not something added by a PO.
Anyone else got the same layout and know where that wire goes?

 

[Stu Jackson]

Unless someone knows FOR SURE, take it off and see what doesn't work.

 

[marchem]

Unless someone knows FOR SURE, take it off and see what doesn't work.

That is probably what I'll end up doing, even if I hear from someone here.

 

[Benny17441]

Try and backtrack the wiring from the windlass. Would not see any other need to run a #4 wire forward.

 

[JK_Boston_Catalina310]

Interesting. You actually have two extra 4 awg black wires from the "standard" setup. All the grounding typically occurs through the engine. The wiring diagram only shows one 1/0 awg wire going from the batteries to the block and then from the block to the buss behind the electric panel.

As others have said, I would start by tracing as much as you can. You can try the disconnect and see what stops working but be careful, by doing this on the negative side the item will still be getting power and could ground out through other ways.

Good luck

 

[marchem]

Interesting. You actually have two extra 4 awg black wires from the "standard" setup. All the grounding typically occurs through the engine. The wiring diagram only shows one 1/0 awg wire going from the batteries to the block and then from the block to the buss behind the electric panel.

As others have said, I would start by tracing as much as you can. You can try the disconnect and see what stops working but be careful, by doing this on the negative side the item will still be getting power and could ground out through other ways.

Good luck

The wiring diagrams I got from the owner's manual don't specify the wire size for the ground from the battery to the engine block (although it must be 1/0). They do show a #4 coming off the DC ground bus, but it's not obvious if it ends at the engine block or the battery terminal. Of course "standard" is a pretty fluid thing in the sailboat manufacturing business.

The wiring for the windlass is shown on one drawing with the switch on the hot side, and nothing showing where the ground for the windlass goes. Another drawing shows hot running direct to the windlass, then back to the switch on the ground side, which doesn't make a lot of sense, then back to the small DC bus. I'll be spending some time soon tracking this down.

 

[Johnb]

and could ground out through other ways.

Good luck

And burn up an undersized wire back to the ground/negative

 

[marchem]

Mystery solved!
Yesterday I put new lugs on all the negative cables in the battery compartment, added a negative buss and battery shunt, and tracked down and labeled all of the grounds. As suspected the mystery wire was from the windlass. Not sure why it followed the path it did, but now I know.

I also learned that new cable is much easier to cut and strip than old, even with the tools Maine Sail recommends. Sure was fun to make a bunch of 1/0 crimps on the heavy duty lugs!!

Next job is doing the same for the positive cables, plus adding fusing.