how is a 2-position battery switch wired?

Discussion in 'Electrical Systems' started by Tim.M, Apr 27, 2009.

  1. Tim.M
    Joined: Apr 2009
    Posts: 48
    Likes: 1, Points: 0, Legacy Rep: 37
    Location: Wisconsin

    Tim.M Junior Member

    I have two batteries and two engines, currently with one battery directly connected to each engine. Certain pumps and accessories are tasked with each battery which I don't like. I'd like both batteries to be able to power bilge pumps in case one battery fails, or to start either engine in case a battery fails.

    I believe what I need to do is to add two battery switches that have a 1, 2, or All selection on each switch. What is the correct way to wire these:

    Code:
    Battery 1 <->\
                  Battery Switch <---------------------> Engine 1
    Battery 2 <-------------->/
    
    Battery 2 <->\
                  Battery Switch <---------------------> Engine 2
    Battery 1 <-------------->/
    
    or
    Code:
                                /<---------------------> Engine 1
    Battery 1 <-> Battery Switch 
                                \<-------------------------------> Engine 2
    
                                /<---------------------> Engine 2
    Battery 2 <-> Battery Switch 
                                \<-------------------------------> Engine 1
    
    I tried to make the lines approximate the length of wire required in each case to put the battery switch in an easy to reach spot.
     
  2. Tim.M
    Joined: Apr 2009
    Posts: 48
    Likes: 1, Points: 0, Legacy Rep: 37
    Location: Wisconsin

    Tim.M Junior Member

    Ok, I found one graph indicating the latter. The common on each switch goes to each engine starter. 1 on each switch goes to battery 1. 2 on each switch goes to battery 2. Position the switches close together and it takes no more wire than scenario one.
     

    Attached Files:

  3. Tim.M
    Joined: Apr 2009
    Posts: 48
    Likes: 1, Points: 0, Legacy Rep: 37
    Location: Wisconsin

    Tim.M Junior Member

    For early 1990's Mercruiser 350 5.7 liter engines, do I need Alternator field disconnect (AFD) on the battery switches?
     
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