Alternator output wiring to bat switch or direct?

Discussion in 'OnBoard Electronics & Controls' started by sdowney717, Nov 5, 2014.

  1. sdowney717
    Joined: Nov 2010
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    Location: Newport News VA

    sdowney717 Senior Member

    Currently, the outputs from the twin engines alternators runs through lower and upper bridge ammeters as 4 gauge wire. Yes it is a long circuit!

    The wire then comes back to the circular off-both-1-2 battery selector switch where it attaches directly to the inputs, one wire on each of two battery bank circuits. So the selector switch never can disconnect that alternator charging wire.
    The output from the boat's AC battery charger has 3 banks. 2 banks are also joined to this alternator output wire. The third charger output wire charges the gen battery.

    I understand maybe why they did this, as in do not disconnect the alternator output wire when it is producing power or maybe shorts alternator?. Of course turning selector switch to off, means engine will stop.

    Originally these alternators were Motorola with separate regulator, I changed them to higher output Delco with internal regulator (they are one wire type).

    And if you only had one battery connected, with both engines running, one alternator output would not be hooked to battery.

    So I was thinking why not just run these 2 alternator output wires into the positive buss bar and let the selector switch be able to disconnect that alternator output circuit.

    Any thoughts?
     
  2. sdowney717
    Joined: Nov 2010
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    Location: Newport News VA

    sdowney717 Senior Member

    Thinking through the details, I will just add an 80 amp fuse in the line for each alternator right near the selector switch.
    Alternators are current limited, they will put out as much as they can and that is it.
    I dont want to stop the batteries charging if selector switch is set to off.
    I dont want one bank on the charger forced to charge 2 banks.
     
  3. gonzo
    Joined: Aug 2002
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    Location: Milwaukee, WI

    gonzo Senior Member

    Alternators are usually hooked up to the switch. That is why the switches are "make before break". That is, they connect to a battery before disconnecting from the previous one. Not having a way to disconnect the alternators makes it dangerous to work on the engines, unless you disconnect the cables at the batteries. Also, you don't have the option of charging only one battery at a time. Further, unless there is a diode bridge, the battery switch is bypassed.
     
  4. sdowney717
    Joined: Nov 2010
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    Location: Newport News VA

    sdowney717 Senior Member

    Pros and cons are everywhere.
    So consider I have twin engines, 2 main battery banks, a selector switch and a 3 bank charger.

    I uploaded a circuit schematic of how it is currently designed.
    I want to add 80 amp fuses in each alternator line near the selector switch.
    Been like this since before I owned the boat.
     

    Attached Files:

  5. sdowney717
    Joined: Nov 2010
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    Location: Newport News VA

    sdowney717 Senior Member

    Alternative could be like this.
    BUT, does any problem occur with running both charger banks into one connection point??

    This one dumps all power from charge and alternators to the common bus bar. Why does the charger have 3 banks if all you need do is split the output from it?
    Charger is made by Raritan.

    Which diagram is best?
     

    Attached Files:

  6. sdowney717
    Joined: Nov 2010
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    Location: Newport News VA

    sdowney717 Senior Member

    Come up with another way which would allow both alternators to charge one or more batteries. Which might be a good idea, seeing I can run on number 1 position yet still charge that #1 battery from bot alternators at the same time.
    Simply move charger wires onto selector switch.
    And if switch set to off, then alternators loose 12volt power.

    So I think either the first or last diagram are best.
    Does anyone see a problem?

    Edit, I dont think I will do this as I dont want to buy more OCPD fuses! (the long wire to the charger)
     

    Attached Files:


  7. sdowney717
    Joined: Nov 2010
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    Location: Newport News VA

    sdowney717 Senior Member

    I think I settled on this, keeps a starter bank and a house bank separate usage but can be joined-turned off if out of power.

    I dont need more than one battery to start 2 engines.
    And cant blow alternators if switch turned off.
    There are so many ways to connect things, it can get too complex. This is simple, no need of ACR relays, and I can comprehend it which is important (kiss principle).

    [​IMG]

    If I move the second house positive wire to number 2, then I can unparallel the house banks batteries. Which I think is good idea for testing if one goes down.
    That means starter bank switch set to number 1.
    And house bank switch set to both to put the 2nd house battery into the charge wire.
     
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