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Can you extend battery “feed lines”?

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    Can you extend battery “feed lines”?

    As some of you know I decided to replace my “fried” GC2 AGM batteries with Costco GC2s and a watering system. I also decided to add two more batteries. In the process I had to replace the main “welding cable” 4/0 lines the inverter battery switch to the house batteries with tinned copper marine cable. What I failed to consider was the now obvious move on the house bank for stbd to port to offset the 4788 port-side list. In order to do so without spending yet more money on cable is there a safe, ABYC approved way for me to virtually add on to the new cable in order to reach the proposed new battery location? I do have Calders book and I will delve into it but I thought I’d crowd-source some background from the group.

    One other thought - even thought the additional battery boxes cost almost as much as the batteries I’m giving serious consideration to adding one more pair to bring the total to 1050Ah. That would add another 135lb in the ass end of the boat but it would clearly give me freedom from the generator except to cook or run heat/AC. That’s assuming we run the engines enough to bring the charge back up so then there’s the whole charging side to consider; even so, it would mean less generator time to recharge according to Mr Calder.

    Anyway - can I put a shunt or something “in the middle” and simply add on the 2+ feet of cable I’d need to connect the bank if I move it to the port side?
    Patti & Gordon Lewandowski
    Sammamish WA
    1998 4788 (April 2018)
    ”Knot Home”

    #2
    My understanding is the cable size is nearly strictly length driven. However, I’ve also discovered there is some trade off with high strand count braided cable like is used in cars with 25 million watt amplifiers and super huge speakers. It also depends on how the total distance of the circuit is counted. Fuzzy knowledge here, but, if the positive and negative each go from the inverter to the batteries, then that is how your cable should be sized. On that total distance, not just to or from. On the other hand, if the batteries feeding the inverter are grounded to the engine and the inverter is grounded to the engine, then only the distance from the batteries to the inverter plus back to the engine are counted. At least that’s what my marine electrician explained when he looked at my system.
    So, that’s nice but what does it mean for you? My understanding is, you will first need to assess what the additional four feet of cable will do to your cable size requirement, then you can use an electrical connection post as a place to connect the cables. The ground wire to me is not a big risk and another cable can be added to ground to the nearby engine. The positive, however, is a bit of a concern and I’d be tempted to use a battery switch as the connector. With that you could isolate that set of batteries to hold in reserve if need be, while not having a risk of an accidental short because some loose gear made contact with a connecting post. One thing for sure, all connections are to be mechanical and solder isn’t allowed.
    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


      #3
      Originally posted by Knothome4788 View Post
      Anyway - can I put a shunt or something “in the middle” and simply add on the 2+ feet of cable I’d need to connect the bank if I move it to the port side?
      Yes, you can use either one of these:
      https://www.bluesea.com/products/cat...tors/PowerPost
      https://www.bluesea.com/products/cat...Dual_PowerPost

      Keep in mind that the cable size guidelines still need to be met: https://www.westmarine.com/WestAdvis...e-And-Ampacity

      1999 3788, Cummins 270 "Freedom"
      2013 Boston Whaler 130 SS
      Anacortes, WA

      Comment


        #4
        Cable size isn’t an issue. I’m using 4/0 which is oversized for the use case and the extra 2-3 feet is well within the safety ratings. What I could find on line was the impact of a splice or the use of 4/0 butt connectors on impedance and therefore use in my situation. Well it’s another day and I will need to dig through the Calder book. Thanks for the input!
        Patti & Gordon Lewandowski
        Sammamish WA
        1998 4788 (April 2018)
        ”Knot Home”

        Comment


          #5
          Originally posted by Knothome4788 View Post
          Cable size isn’t an issue. I’m using 4/0 which is oversized for the use case and the extra 2-3 feet is well within the safety ratings. What I could find on line was the impact of a splice or the use of 4/0 butt connectors on impedance and therefore use in my situation. Well it’s another day and I will need to dig through the Calder book. Thanks for the input!
          As long as the butt splice or ring terminals are properly crimped-on and, in the case of ring terminals, the nut is properly torqued, the resistance will be less than that of the cable. This is by design: the internal surface area of a crimp-on splice or connector and the surface area of a ring connector are much larger than the area of the conductors.
          1999 3788, Cummins 270 "Freedom"
          2013 Boston Whaler 130 SS
          Anacortes, WA

          Comment


            #6
            I don’t profess to be a battery or electrical expert here, but when we owned a M490, we had 6 - L16 AGM batteries in the Stbd lazarette, and none on the Port side. We used 4.0 cable up to positive and negative connecting studs mounted high on the lazarrete bulkhead, and 4.0 cable to the inverter mounted forward of the Stbd muffler.
            The balance of the boat was nice with no sign of the ‘normal’ list to Port that these boats tend to have.

            One of our dock neighbors with a 4788 mounted his house batteries in the machinery room near the hot water tank to try to better balance the boat. Access to the engine room in that case was through the center cut panel in the salon.
            Rob
            Bayliner 5788
            'Merlin V'
            Vancouver BC

            Comment


              #7
              Thanks again guys! When I'm at the boat in a couple weeks I need to check what all else is connected to the batteries in their current location (pun not intended). If it's only the cables and inverter/charger temp sensor (and assuming there is extra wire for that) I'll probably move the whole kit and caboodle to the stbd side. If there is too much other stuff I'll just suck it up, keep it simple, change out the AGMs and add the extra pair - all on the port side. Once that's all done I'll order the watering components from Battery Watering Systems or one of their dealers.
              Patti & Gordon Lewandowski
              Sammamish WA
              1998 4788 (April 2018)
              ”Knot Home”

              Comment


                #8
                Gordon,

                You can use something like this to connect light loads and extend the cables at the same time: https://www.bluesea.com/products/cat...PowerPost_Plus. The cables for heavier loads can be connected directly to the stud, ABYC 11.14.4.1.10 states, "No more than four terminals shall be secured to any one terminal stud. If additional connections are necessary, two or more terminal studs shall be connected together by means of jumpers or copper straps." Alternatively you may be able to use buss bars to extend the cables and connect additional loads: https://www.bluesea.com/products/category/18/BusBars.

                Don't forget to protect the circuits with fuses or breakers.
                1999 3788, Cummins 270 "Freedom"
                2013 Boston Whaler 130 SS
                Anacortes, WA

                Comment


                  #9
                  Great. Thanks! I already have a 250A fuse on the main 4/0 cable. After taking normal safety precautions it looks like I simply need to disassemble all current cabling, install the appropriate stud or bus bar, connect the existing cables and then start the new location installation from there. Again this assumes that I don’t have a mess of other wires to deal with but IIRC the installation is pretty clean so I should be okay. I will start a thread and post a lot of pictures in case others are interested. No more listing to port!!!
                  Patti & Gordon Lewandowski
                  Sammamish WA
                  1998 4788 (April 2018)
                  ”Knot Home”

                  Comment


                    #10
                    Whats wrong with using a butt splice?

                    Comment


                      #11
                      As I now know there is nothing wrong with a butt splice. Since some of the cabling is already made up I decided to use a Blue Sea DualPower Post cable connector. It fits may application perfectly. https://www.fisheriessupply.com/blue...onnectors-2016.

                      Thanks to all all you guys and some Calder reading I know a bit more about 12v electrical systems.
                      Patti & Gordon Lewandowski
                      Sammamish WA
                      1998 4788 (April 2018)
                      ”Knot Home”

                      Comment

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