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    Alternator to battery switch panel wire size

    I'm installing a 180 amp delco to replace my dead denso alternator on the starboard engine. The factory wired with what appears to be a #10 wire from the output, batt lug, of the starboard alternator to the accessory switch on the battery selector panel. The port engine alternator battery wire is connected to the battery cables at the starter solenoid. My presumption is this was done so the accessory and starting batteries each has a dedicated charging circuit. Now that I'm increasing the amperage, larger gauge wire is required. I'm looking at using #4 braided wire similar to welding wire or 12v amplifier wire. Really soft to bend, oil resistant insulation, lots and lots of strands. That was the plan until I learned that the accessory wire goes the full distance between the alternator and the panel. That takes the distance from about six feet to more like 25. Down the outboard side of the engine then across to strap onto the battery cable to the panel, cross over between the engines, forward to the bulkhead across in front of the port engine then up and aft to the panel.
    My backup plan would be to put the Delco on the port engine and connect it to the accessory circuit and move the remaining denso to the starboard engine and connect it at the starter to the starting circuit. This would save about half of the distance.
    There is, of course, the difference of voltage drop over distance, but much of that is mitigated by the high strand count. I've looked at the available tables with little resolution. So, what are the opinions of the brain trust?
    P/C Pete
    Edmonds Yacht Club (Commodore 1993)
    1988 3818 "GLAUBEN”
    Hino EH700 175 Onan MDKD Genset
    1980 Encounter Sunbridge "Misty Blue" (Sold)
    MMSI 367770440
    1972 Chevrolet Nova Frame off Resto-mod in the garage
    Boating on the Salish Sea since 1948

    #2
    I used 4 gauge on my 110 amp alternators and heavy duty lugs.
    Batteries are all 2/0 cable.
    Pat says: DO-IT-RIGHT THE FIRST TIME!

    Bayliner 3870 "ALASKA33)
    Twin 350 GM power
    Located in Seward, AK
    Retired marine surveyor

    Comment


      #3
      Pete,
      For 180 amps you need 3 ot copper wire which Is rated for 200 amps. I would run the cable from the alternator across the bulkhead in front of the engine to the battery switch panel. That how mine is run from the factory.
      Gibraltar, Mi.
      1986- 3870- Hino 175's - Just purchased May ,2017
      34' Tollycraft- sold
      88 26' Shamrock/ Diesel
      14' Zodiac Bay Runner

      Comment


        #4
        It all depends on the length of the run. Have a look at this link. https://www.google.ca/search?q=marin...kQpCQMB_JdZ2M:
        Remember it is the round trip on this so it is double the length.
        2002 2859 "Liquid Therapy"
        Moored at Reed Point Marina in Port Moody BC

        Comment


          #5
          .................
          Originally posted by Pcpete View Post
          I'm installing a 180 amp delco to replace my dead denso alternator on the starboard engine.
          Pete, unless this is a high dollar Balmar or ______, I highly doubt that you will see 180 Amps from this Delco unit.
          It may produce a high output for a short duration, but it will cut back quickly.


          The factory wired with what appears to be a #10 wire from the output, batt lug, of the starboard alternator to the accessory switch on the battery selector panel. The port engine alternator battery wire is connected to the battery cables at the starter solenoid.
          Yes, that is very common, and it also keeps the length of the "charge lead" conservatively short.


          My presumption is this was done so the accessory and starting batteries each has a dedicated charging circuit. Now that I'm increasing the amperage, larger gauge wire is required. I'm looking at using #4 braided wire similar to welding wire or 12v amplifier wire. Really soft to bend, oil resistant insulation, lots and lots of strands. That was the plan until I learned that the accessory wire goes the full distance between the alternator and the panel. That takes the distance from about six feet to more like 25. Down the outboard side of the engine then across to strap onto the battery cable to the panel, cross over between the engines, forward to the bulkhead across in front of the port engine then up and aft to the panel.
          My backup plan would be to put the Delco on the port engine and connect it to the accessory circuit and move the remaining denso to the starboard engine and connect it at the starter to the starting circuit. This would save about half of the distance.
          There is, of course, the difference of voltage drop over distance, but much of that is mitigated by the high strand count. I've looked at the available tables with little resolution. So, what are the opinions of the brain trust?

          If this Delco unit is to be dedicated to your HLBB (house load batt bank), I would increase the charge lead as well as the alternator chassis Negative cable (the small cable that runs from the alt chassis to the engine block).
          I would then take the charge lead to the "Common" cable where it attaches to your starter motor lug.
          Now the alternator current travels only a short distance until it reaches the much larger "Common" cable, of which in turn will direct the charge to the bank selected.
          Rick E. Gresham, Oregon
          2850 Bounty Sedan Flybridge model
          Twin 280 HP 5.7's w/ Closed Cooling
          Volvo Penta DuoProp Drives
          Kohler 4 CZ Gen Set

          Comment


            #6
            Bounty, thanks. The old denso died last spring, but I thought it was the starting circuit alternator, so I didn't mess with it until Christmas. I only learned it was for the house batteries a couple days ago. Our house batteries are 4 golf cart and our inverter is is on a separate set of 4 golf cart batteries that is not connected to any of the engine charging system.
            If I were to change the batt wire to connect at the starter lug, the house batteries would have no connection to either alternator. I almost never use the combining switch largely because of the difference between the starting battery system and the house system and no adiquate isolator.
            I went with the delco I have because it was very close to the same price as the smaller amp unit and connects very similar to the denso. I agree that there's almost zero chance of the alternator reaching max output, but I want the system to be capable.
            P/C Pete
            Edmonds Yacht Club (Commodore 1993)
            1988 3818 "GLAUBEN”
            Hino EH700 175 Onan MDKD Genset
            1980 Encounter Sunbridge "Misty Blue" (Sold)
            MMSI 367770440
            1972 Chevrolet Nova Frame off Resto-mod in the garage
            Boating on the Salish Sea since 1948

            Comment


              #7
              ...................
              Originally posted by Pcpete View Post
              Bounty, thanks. The old denso died last spring, but I thought it was the starting circuit alternator, so I didn't mess with it until Christmas. I only learned it was for the house batteries a couple days ago.
              Our house batteries are 4 golf cart and our inverter is on a separate set of 4 golf cart batteries that is not connected to any of the engine charging system.
              That sounds rather strange to me.
              Your HLBB should receive an alternator charge, especially (and ASAP) after a load draw down.

              And by the way...... a starter motor Amp Hour draw is relatively low. A load of 200 amps for 6 seconds, is less than 1 Amp Hour.
              Add a bit for glow plugs..... and it's still relatively low in terms of Amp Hours.

              In other words, High Amp alternators are best suited for the HLBB side of the system..... not necessarily for the SLBB side.



              If I were to change the batt wire to connect at the starter lug, the house batteries would have no connection to either alternator.
              Knowing full well that your 38 footer 12 vdc system is not quite the same as with a 28 footers and smaller, if your alternator(s) send the charge rate directly to the "common" cable, you then allow the common cable to send the charge rate to the battery bank that has been selected via your MBSS or BS.


              I almost never use the combining switch
              Please explain..... combing switch! Is this a switch that activates a combining solenoid, or other????

              .......... largely because of the difference between the starting battery system and the house system
              Keeping in mind that we always want to maintain a "reserve", any two 12 volt batt banks can be combined.

              ......... and no adequate isolator.
              Isolators are old school and offer a .6 to .7 voltage loss.
              I would suggest using an ACR or VSR in it's place.



              I went with the delco I have because it was very close to the same price as the smaller amp unit and connects very similar to the denso. I agree that there's almost zero chance of the alternator reaching max output, but I want the system to be capable.
              Understood!
              Rick E. Gresham, Oregon
              2850 Bounty Sedan Flybridge model
              Twin 280 HP 5.7's w/ Closed Cooling
              Volvo Penta DuoProp Drives
              Kohler 4 CZ Gen Set

              Comment


                #8
                Bounty, your thoughts are right on, however, I'm failing at some of my description. My starting batteries are a pair of 31's in parellel, currently charging from the port engine with the alternator battery wire going to the starter lug. My house/accessory batteries are four golf cart, two each in series then the pairs in parellel, normally charged from the starboard alternator with the alternator battery wire going to the accessory switch on the battery control panel. On that panel are four battery switches and some breakers, never mind the breakers. Left to right, first the generator has a #1, #2 and both selection and is connected to a dedicated 24 series battery. The three other switches are all on/off only starting with the starting 31 series batteries, then a switch to combine the house and starter sets, lastly the house/accessory switch. Completely separate, there is the inverter battery system. It has its own four golf cart battery system and is recharged with either shore power or off the generator.
                With this configuration the starter cables only go to the starter switch, so from what I can see, if both alternator battery wires went to the starter battery lug, only the starting batteries would be charged. I agree that an ACR or VSR is in my future, and may be the easiest solution, more research required.
                P/C Pete
                Edmonds Yacht Club (Commodore 1993)
                1988 3818 "GLAUBEN”
                Hino EH700 175 Onan MDKD Genset
                1980 Encounter Sunbridge "Misty Blue" (Sold)
                MMSI 367770440
                1972 Chevrolet Nova Frame off Resto-mod in the garage
                Boating on the Salish Sea since 1948

                Comment


                  #9
                  Pete, I don’t know the 12v DC electrical layout of your 38 but could the new 180 amp alternators charge lead connect directly to the house battery bank instead of running to the panel?
                  Does that save you any distance?
                  Dave
                  Edmonds, WA
                  "THE FIX"
                  '93 2556 5.7 Bravo II 2.0:1 18 1/4x19 P
                  (.030 over-Vortec top end-part closed cooled)
                  The rebuild of my 2556 https://www.baylinerownersclub.org/f...76?view=thread
                  Misc. projects thread
                  https://www.baylinerownersclub.org/f...56-gctid789773

                  Comment


                    #10
                    Builderdude, not really. I'm going to swap the alternator locations, the 180 on the port engine, then revise that batt wire to go to the panel with #4 braided wire. Then I'll install the denso on the starboard engine and revise that batt wire to connect at the starter. We are going to have to meet up one of these days.
                    P/C Pete
                    Edmonds Yacht Club (Commodore 1993)
                    1988 3818 "GLAUBEN”
                    Hino EH700 175 Onan MDKD Genset
                    1980 Encounter Sunbridge "Misty Blue" (Sold)
                    MMSI 367770440
                    1972 Chevrolet Nova Frame off Resto-mod in the garage
                    Boating on the Salish Sea since 1948

                    Comment


                      #11
                      Pete, would you be able to arrange these icons and then draw in the cables and wires as per your system, or as per what you propose?
                      MS Paint is fairly simple to use.






                      Click image for larger version

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                      Perhaps come up with something similar to these schematics!

                      Examples ONLY



                      Click image for larger version

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                      Again.... Example ONLY!


                      Click image for larger version

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                      Rick E. Gresham, Oregon
                      2850 Bounty Sedan Flybridge model
                      Twin 280 HP 5.7's w/ Closed Cooling
                      Volvo Penta DuoProp Drives
                      Kohler 4 CZ Gen Set

                      Comment


                        #12
                        Originally posted by Pcpete View Post
                        Builderdude, not really. I'm going to swap the alternator locations, the 180 on the port engine, then revise that batt wire to go to the panel with #4 braided wire. Then I'll install the denso on the starboard engine and revise that batt wire to connect at the starter. We are going to have to meet up one of these days.
                        Pete...if I understand what you said above, you're going to swap the charging functions of the two engines...? The port will charge house and starboard will charge start...? Not sure that's a good idea...

                        Have you considered the rest of the wiring and cross-connects (I think you called them "combining") and generator outputs...?
                        1988 3888 "Liberty"
                        Twin Cummins 6BT's 210hp
                        Onan 8.0
                        Boating Raritan Bay

                        Comment


                          #13
                          Nickp, yeah, I've looked very carefully at which does what and will be answering builderdudes question later when I can use the house laptop. This poor old iPad isn't supported with software updates and can't load most of the paint type apps. I have one that's newer but it got in the mechanism of my chair and it looks like it was used for target practice, the repair shop just laughed.
                          P/C Pete
                          Edmonds Yacht Club (Commodore 1993)
                          1988 3818 "GLAUBEN”
                          Hino EH700 175 Onan MDKD Genset
                          1980 Encounter Sunbridge "Misty Blue" (Sold)
                          MMSI 367770440
                          1972 Chevrolet Nova Frame off Resto-mod in the garage
                          Boating on the Salish Sea since 1948

                          Comment


                            #14
                            Originally posted by Pcpete View Post
                            Nickp, yeah, I've looked very carefully at which does what and will be answering builderdudes question later when I can use the house laptop. This poor old iPad isn't supported with software updates and can't load most of the paint type apps. I have one that's newer but it got in the mechanism of my chair and it looks like it was used for target practice, the repair shop just laughed.

                            Gotcha...it just sounded like you were going to wind up doing what you wanted to avoid...the 25 ft run from the Stdb alternator would now need to be done with the Port alternator...
                            I can wait to see your wiring diagram...for now, I'm gonna go mix me up a fruit slurpy...put my Ninja to work...I could use a bit of brain freeze...LOL...
                            1988 3888 "Liberty"
                            Twin Cummins 6BT's 210hp
                            Onan 8.0
                            Boating Raritan Bay

                            Comment


                              #15
                              Click image for larger version

Name:	587635C9-9DDA-470D-81A1-8C0409644FD0.jpeg
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ID:	480179 Builderdude, here are the simplistic drawings of how the battery system is, then going to. I left out the inverter and generator systems.
                              P/C Pete
                              Edmonds Yacht Club (Commodore 1993)
                              1988 3818 "GLAUBEN”
                              Hino EH700 175 Onan MDKD Genset
                              1980 Encounter Sunbridge "Misty Blue" (Sold)
                              MMSI 367770440
                              1972 Chevrolet Nova Frame off Resto-mod in the garage
                              Boating on the Salish Sea since 1948

                              Comment

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