3rd battery "4th wire" connection?

[Fun Time]

Got a quick question from a neightbor... He has a Rinker 31' Fiesta Vee. It has a Generator. He has 3 batteries and forgot to label things before Winterizing. Now... he has 4 Red wires and 3 Black wires and doesn't remember where to put the 4th Red? Is it a jumper from one battery to another or ??? Any help on how that 4th Red wire gets connected??? Thanks.

 

[Billylll]

More information is needed.
It could be a stand alone red wire for equipment added by the previous owner.
If it was a jumper to tie 2 batteries together it would be just that and could be confirmed by tracing both ends of the wire. If it's a jumper it would probably be short in distance assuming the batteries are mounted close together.
Many times a Thruster or Windlass wire are wired directly to one of the batteries. This isn't a great idea because the round trip of the wire increases it's resistance and current draw if not properly sized.
Are the red battery wires all the same size? Many times the generator will be a smaller gauge wire then the starting batteries for the engines.
Bill

 

[Fun Time]

Thanks. The answer was it was for the Generator. Thank you me fellow RO. Peace.
Rich