Boat Dual Battery Wiring

Discussion in 'OnBoard Electronics & Controls' started by mikealston2428, Apr 17, 2024.

  1. mikealston2428
    Joined: Jul 2011
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    Location: aussie

    mikealston2428 Senior Member

    Hi All,
    Ive got a dual battery setup and have had to replace the crank battery as it died
    Silly me didn't take much notice of where wires were connected on the 2 batteries
    All the house battery wires I'm fine with
    Ive got x2 POS and x2 NEG thick gauge engine wires connected to the battery switch
    Do all 4 of these engine wires go to the crank battery ?
    Also the POS and NEG for the anchor winch go to the crank battery, Is this correct

    Many Thanks,
    Mike
     
  2. C. Dog
    Joined: May 2022
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    Location: Coffs Harbour NSW Australia

    C. Dog Senior Member

    Mate you are really asking how long a piece of string is here, there are few hard and fast rules due to different systems and needs.

    How about a clear mud map of what you have and where the wires you're unsure of head?

    Main earths do not go onto isolators, normally directly onto the battery post.

    @Admin is it possible to influence the initial information offered by people needing help?

    It is not the job of the inexperienced to know what experts need to help them, but it is also frustrating extracting required information, sometimes a sentence a post, in order to perform the actual work of offering advice. I'm thinking we could offer guidelines upon joining with the top bullet "Pictures, pictures and more pictures"?
     
    fallguy, BlueBell and Barry like this.
  3. mikealston2428
    Joined: Jul 2011
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    Location: aussie

    mikealston2428 Senior Member

    Hi C.Dog
    Hope you are well
    OK so has I said Ive got x2 POS and x2 NEG thick gauge wires left to hook up to the dual batteries and im not sure how to connect them correctly
    Ive traced all these wires
    The x2 NEG wires both bypass the battery switch and run back to the inboard motor
    Earthing out on the engine block 1 each side of the engine
    The x2 POS wires both run to diffrent terminals on the battery switch
    And there is a small lenght of NEG heavy gauge wire that Im asumming connects to the NEG post on each battery
    Hope this all makes sence and someone can tell me were to connect these wires on the 2 batteries
    Many thanks
    Mike
     
  4. seasquirt
    Joined: Dec 2015
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    Location: South Australia

    seasquirt Senior Member

    Hi Mike, nobody here wants to be party to you accidentally blowing up batteries, or your alternator / generator, or your boat, or yourself, so please take and post photos of your batteries, with pos and neg posts clearly identified, the thick bridge wire(s), your isolators, and a close up of your wiring diagram for your model boat, and engine if available; or at least like C.Dog asked, a hand drawn wiring diagram for all wires leading to the battery area, and where they go to at the other end. Are your batteries common lead acid, or maybe calcium batteries, or something else ? Is it a 12 Volt system or 24 Volt, or something else ? There can be so many variables without specific information, and photos, to know what to tell you. A picture is worth a thousand words; many pictures will help greatly.
     
  5. Barry
    Joined: Mar 2002
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    Barry Senior Member

    And include the picture of the terminals on the battery switch as well as the face, Ie is there a 1) off positsion 2) #1 for battery one 3) #2 for battery two 4) Both for combining both start batteries
    Also, your reference to "thick wires" what is the gauge and the distance from the batteries to the starters.

    Is there a "combining" switch? Ie to tie in the house to the start system if the start batteries are dead?

    Ditto on C.Dog's post 2 and Seasquirts post 4
     
  6. C. Dog
    Joined: May 2022
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    Location: Coffs Harbour NSW Australia

    C. Dog Senior Member

    @Barry you don't need a "combining switch" to do this if he has two of the four position manual isolators, a cable between the two isolator switches will perform this with both switches in the correct positions. I've forgotten the exact layout now, but ic can be deduced and probably found online.

    @mikealston2428 the negatives are always easy and there are cables from engine earths to -ve posts on each battery and one between the two batteries, virtually impossible to get wrong as long as they go on -ve battery posts.

    The +ves are, pick a battery for bank 1 and the other becomes bank 2, then place their +ve cables on appropriate isolator terminals, then the "both" setting brings both cranking batteries into play, easy peasy really. Edit: there will be another cable from the output terminal on the switch to the starter solenoid. Also never move the engine switch through "off" with it running as you will fry the alternator rectifier and lose charging.

    Then as @Barry said, you can join auxiliary and cranking banks via switching for extra redundancy, especially after overnight anchoring or other high drain situations. It does not require a third switch, though heading into the "old man" category sees me forgetting more than I remember, but it will be easily worked out if you want to do it.

    After all of this spaghetti returns to its correct circuits I suggest an accurate wiring diagram sealed in a plastic sleeve and left aboard may save future angst. I bet the internet has them in abundance(sans plastic sleeve).

    Best of luck fellow boating person.
     
    Last edited: Apr 18, 2024
  7. mikealston2428
    Joined: Jul 2011
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    mikealston2428 Senior Member

    Hi C.Dog,

    That all makes sense thank you
    The anchor winch connects to the crank battery is this correct
    And all the house wires just go to the house battery is this correct
    Thanks
    Mike
     
  8. C. Dog
    Joined: May 2022
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    Location: Coffs Harbour NSW Australia

    C. Dog Senior Member

    Like I said initially Mike, there are few hard and fast rules in these systems.

    Some lead acid batteries are designed to offer low power output and will cope with deep discharge cycles at low amperage output. Often used as auxilliary batteries and often called Deep Cycle.

    Then there are cranking batteries that can supply the high power demands of starter motors which can be around 300A at 12V (3600 watts). They need to be kept charged to near optimum voltage or sulphation deposits can cause the battery to fail.

    I suggest your anchor winch is connected to cranking batteries because of its high power but relatively low duty cycle, like a starter. I also suggest you have your engine running when you're raising or lowering anchor, generally it would be anyway.
     
  9. C. Dog
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    Location: Coffs Harbour NSW Australia

    C. Dog Senior Member

    Sorry didn't notice question re house wires, generally it would be as you suspect, but I didn't design the electrical circuit so no guarantee. Little can go wrong however as long as you dont add an accidental short circuit by mixing +ve and -ve.
     
  10. mikealston2428
    Joined: Jul 2011
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    mikealston2428 Senior Member

    Many Thanks C.Dog
    Your advice is greatly appreciated
    Thanks
    Mike
     
    C. Dog likes this.

  11. C. Dog
    Joined: May 2022
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    C. Dog Senior Member

    Most welcome Mike.
     
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