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  • Is 8 awg enough?

    Now that I am back from my work trip, I am going to installed my two UT1300 batteries on the passthrough of my 2021 Imagine 2800BH. It looks like GD is using 8 awg from the battery to the distribution panel. My question is can that size wire really handle the 12V loads from the trailer or should I be looking to upgrade to 6 awg. By the way the stock converter/charger is going to be disconnected a 60 amp lithium charger install close to the batteries.
    2018 RAM 3500 Big Horn, CC SB 6.7 Cummins HO/Aisin
    2021 GD Imagine 2800BH

  • #2
    Originally posted by Giesis View Post
    Now that I am back from my work trip, I am going to installed my two UT1300 batteries on the passthrough of my 2021 Imagine 2800BH. It looks like GD is using 8 awg from the battery to the distribution panel. My question is can that size wire really handle the 12V loads from the trailer or should I be looking to upgrade to 6 awg. By the way the stock converter/charger is going to be disconnected a 60 amp lithium charger install close to the batteries.
    If I remember correctly, this was a discussion (offline) between the moderators and Grand Design. GD assured the moderators that 8 AWG was sufficient and meets code for the expected loads.

    Since you're going to mount your new charger close to your batteries (a good idea regardless) I assume the higher amperage won't travel over 8 AWG wires so it won't be a concern. For anyone considering doing a one-for-one swap of their converter for a lithium-capable converter/charger thus using 8 AWG-I'd be concerned and would urge upgrading the wiring.

    I'm tired, so if that's not worded clearly hopefully someone much smarter than me on this stuff (lots like that here!) will clarify. Jkwilson , TucsonJim are two of many...
    Last edited by howson; 11-15-2020, 07:25 AM.
    Forum moderators are not GD employees--we are volunteers and owners presumably just like yourself. Unless specifically mentioned otherwise, we have nothing to gain should you choose to purchase a product or engage a service we discuss on this forum.

    2017 Ford F-350 DRW, '19 315RLTSPlus

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    • #3
      Originally posted by howson View Post

      If I remember correctly, this was a discussion (offline) between the moderators and Grand Design. GD assured the moderators that 8 AWG was sufficient and meets code for the expected loads.

      Since you're going to mount your new charger close to your batteries (a good idea regardless) I assume the higher amperage won't travel over 8 AWG wires so it won't be a concern. For anyone considering doing a one-for-one swap for their converter for a lithium-capable converter/charger thus using 8 AWG-I'd be concerned and would urge upgrading the wiring.

      I'm tired, so if that's not worded clearly hopefully someone must smarter than me on this stuff (lots like that here!) will clarify. Jkwilson , TucsonJim are two of many...
      Thanks for the reply. I just wanted to make sure. I am using 4awg from the new charger to the batteries.
      2018 RAM 3500 Big Horn, CC SB 6.7 Cummins HO/Aisin
      2021 GD Imagine 2800BH

      Comment


      • #4
        Originally posted by Giesis View Post
        Now that I am back from my work trip, I am going to installed my two UT1300 batteries on the passthrough of my 2021 Imagine 2800BH. It looks like GD is using 8 awg from the battery to the distribution panel. My question is can that size wire really handle the 12V loads from the trailer or should I be looking to upgrade to 6 awg. By the way the stock converter/charger is going to be disconnected a 60 amp lithium charger install close to the batteries.
        I performed this conversion where a single 100ah AIMS battery was used with a 60 amp Progressive Dynamics lithium charger. 4 awg was also used in my rig in the passthrough for battery charging. An ampacity chart is useful when determining wire size based on load.

        For your question in using the OEM 8 awg, I am using the original wiring to power the rig from the passthrough mounted battery with no issues since the loads to run the rig are low. Both my charger and battery were relocated to the passthrough where 4 AWG was used. As a result, the high current charger to the battery is approximately 1.5 ft away. The original WFCO was left in place with the breaker turned off.

        Here is a link to the install methods used on my Imagine.

        https://gdrvowners.com/forum/operati...-lithium-power

        Jim
        Last edited by Guest; 11-15-2020, 09:07 AM.

        Comment


        • #5
          Originally posted by MidwestCamper View Post

          I performed this conversion where a single 100ah AIMS battery was used with a 60 amp Progressive Dynamics lithium charger. 4 awg was also used in my rig in the passthrough for battery charging. An ampacity chart is useful when determining wire size based on load.

          For your question in using the OEM 8 awg, I am using the original wiring to power the rig from the passthrough mounted battery with no issues since the loads to run the rig are low. Both my charger and battery were relocated to the passthrough where 4 AWG was used. As a result, the high current charger to the battery is approximately 1.5 ft away. The original WFCO was left in place with the breaker turned off.

          Here is a link to the install methods used on my Imagine.

          https://gdrvowners.com/forum/operati...-lithium-power

          Jim
          Jim - Thanks for the replay. I am more or less doing what you did and also adding a 30 amp auto-reset in the passthrough. I am leaving the OEM 30 amp in place and using a wire from the positive bus bar to power the jack and the breakaway switch. Since I dont need/want the truck to charge charge the batteries I am disconnecting the 12v aux wire from the 7 pin connector.
          2018 RAM 3500 Big Horn, CC SB 6.7 Cummins HO/Aisin
          2021 GD Imagine 2800BH

          Comment


          • #6
            Giesis ,

            I've done the same where I am using the frame mounted breaker at the front as a junction block now. I installed a 30 amp breaker in the docking station to back feed this wire and installed a Busman 60amp resettable breaker right on top of my battery with industrial Velcro. Both wires on my battery switch were moved to one side of the switch and free side of the switch was connected with 8 awg to the positive busbar and on to the battery with 4 awg welding cable.
            One thing to keep in mind when modifying wiring is your brake system break away switch that connects to the frame mounted breaker is on the copper (battery) side which means it is directly wired to the battery. So my break away switch is currently powered through my battery switch which will now kill all power to the rig.
            The way I plan to get around this is to install a Curt (or similar) brake system break away kit that will incorporate its own dedicated charger and battery. Plan to install it in the spring.

            https://www.ebay.com/i/262730643480?...e44882c3a86bbc

            Similar to the Curt

            https://www.etrailer.com/Trailer-Bre...50-85-313.html

            Jim
            Last edited by Guest; 11-16-2020, 06:15 PM.

            Comment


            • #7
              Originally posted by MidwestCamper View Post
              Giesis ,

              I've done the same where I am using the frame mounted breaker at the front as a junction block now. I installed a 30 amp breaker in the docking station to back feed this wire and installed a Busman 60amp resettable breaker right on top of my battery with industrial Velcro. Both wires on my battery switch were moved to one side of the switch and free side of the switch was connected with 8 awg to the positive busbar and on to the battery with 4 awg welding cable.
              One thing to keep in mind when modifying wiring is your brake system break away switch that connects to the frame mounted breaker is on the copper (battery) side which means it is directly wired to the battery. So my break away switch is currently powered through my battery switch which will now kill all power to the rig.
              The way I plan to get around this is to install a Curt (or similar) brake system break away kit that will incorporate its own dedicated charger and battery. Plan to install it in the spring.

              https://www.ebay.com/i/262730643480?...e44882c3a86bbc

              Similar to the Curt

              https://www.etrailer.com/Trailer-Bre...50-85-313.html

              Jim
              Copy I’ll keep your advise in mind. Thanks
              2018 RAM 3500 Big Horn, CC SB 6.7 Cummins HO/Aisin
              2021 GD Imagine 2800BH

              Comment


              • #8
                To your original question...You can't go wrong using wire a size bigger than what you think is 'good enough'.
                The only downside is your $$ outlay and sometimes finding connectors that will work with the bigger wire.
                Finer strand wire is also better. But...costs even more. DLO, diesel locomotive cable is awesome for current carrying capacity. Costs A LOT.
                2018 Dodge 3500 6.7 Cummins w Aisin and 9 cup holders
                Not to brag or anything about my finances, but my bank calls me about every day to tell me my balance is OUTSTANDING!

                Comment


                • #9
                  I'm attaching chart that shows 8 AWG is "enough" for your application.

                  Most of your rigs have a 30 amp breaker in line with the battery supply line. After the breaker, the wire continues to different branch circuits that divide and carry the load to items such as lights, control boards, furnace fans, etc. The maximum current will be limited by that 30 amp breaker. This is applicable to the general construction of most rigs. There are some rigs such as those with hydraulics that have their own higher current needs. This discussion is not focused on those specific applications.

                  The maximum current expected in the general purpose circuits should be less than 30 amps. If more, the breaker should trip. With that in mind, the next consideration is the length of the circuit from the batteries to the branch circuits and back. Based on what I've seen, this is approximately 8-12 feet, depending on the model. So for the purposes of calculating wire size, I'll use 15 feet.

                  The chart I'm attaching indicates that a 15 foot circuit at 30 amps can anticipate no more than a 3% voltage drop when using 8 AWG. This chart is based on ABYC E-11 requirements which are defined for the boating industry. The requirements are a great guideline for the RV industry, but are not actually called out. A 3% loss means that if your batteries were putting out 13.5 volts DC, you could expect to measure 13.1 volts where the wires branch into their individual circuits.

                  You should be fine with 8 AWG as long as you don't overload the circuit. And if you do overload it, the breaker will helpfully protect you. If you ever add a high draw item such as an inverter, it should have its own appropriately sized wiring connected to the battery and protected with its own fuse or breaker.

                  Click image for larger version

Name:	8 AWG.jpg
Views:	1325
Size:	168.4 KB
ID:	35203



                  Jim and Ginnie
                  2024 Solitude 310GK
                  GDRV Technical Forum Moderator
                  GDRV Rally Support Coordinator

                  Comment


                  • #10
                    Originally posted by TucsonJim View Post
                    I'm attaching chart that shows 8 AWG is "enough" for your application.

                    Most of your rigs have a 30 amp breaker in line with the battery supply line. After the breaker, the wire continues to different branch circuits that divide and carry the load to items such as lights, control boards, furnace fans, etc. The maximum current will be limited by that 30 amp breaker. This is applicable to the general construction of most rigs. There are some rigs such as those with hydraulics that have their own higher current needs. This discussion is not focused on those specific applications.

                    The maximum current expected in the general purpose circuits should be less than 30 amps. If more, the breaker should trip. With that in mind, the next consideration is the length of the circuit from the batteries to the branch circuits and back. Based on what I've seen, this is approximately 8-12 feet, depending on the model. So for the purposes of calculating wire size, I'll use 15 feet.

                    The chart I'm attaching indicates that a 15 foot circuit at 30 amps can anticipate no more than a 3% voltage drop when using 8 AWG. This chart is based on ABYC E-11 requirements which are defined for the boating industry. The requirements are a great guideline for the RV industry, but are not actually called out. A 3% loss means that if your batteries were putting out 13.5 volts DC, you could expect to measure 13.1 volts where the wires branch into their individual circuits.

                    You should be fine with 8 AWG as long as you don't overload the circuit. And if you do overload it, the breaker will helpfully protect you. If you ever add a high draw item such as an inverter, it should have its own appropriately sized wiring connected to the battery and protected with its own fuse or breaker.

                    Click image for larger version

Name:	8 AWG.jpg
Views:	1325
Size:	168.4 KB
ID:	35203


                    The only thing upsizing from 8 gauge would give you is lower voltage drop. Not sure you would need it. 6 gauge would be overkill I think. I used 8 gauge when I installed my second battery.

                    There is a good source of really good quality battery cables online I have used. www.batterycablesusa.com You specify length, color, and end connections and they custom make them for you. And reasonably priced. Re-wired my son's boat and added a second battery and stereo system and sub. Wired my second RV battery using them too.
                    Tony G
                    2020 Chevy Silverado 3500 Highcountry
                    2016 Grand Designs Reflection 303RLS
                    KTM 250XC

                    Comment


                    • #11
                      Originally posted by tgodrich View Post

                      The only thing upsizing from 8 gauge would give you is lower voltage drop. Not sure you would need it. 6 gauge would be overkill I think. I used 8 gauge when I installed my second battery.

                      There is a good source of really good quality battery cables online I have used. www.batterycablesusa.com You specify length, color, and end connections and they custom make them for you. And reasonably priced. Re-wired my son's boat and added a second battery and stereo system and sub. Wired my second RV battery using them too.
                      After a few times of working with "large" battery cables (two different RVs plus a couple buddies) I broke down and bought the crimper and copper lugs to do it myself. I still bought my 4/0 cables premade, but anything 2 gauge or smaller I can make myself and it has been really handy. My crimper isn't made anymore, but is similar to this:

                      https://www.amazon.com/IWISS-Termina...NsaWNrPXRydWU=

                      And Rings like this:

                      https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

                      It is really nice to be able to cut them to length and not have terminals on them when pulling them through the rig.
                      Forum moderators are not GD employees--we are volunteers and owners presumably just like yourself. Unless specifically mentioned otherwise, we have nothing to gain should you choose to purchase a product or engage a service we discuss on this forum.

                      Neil Citro
                      2018 Reflection 28BH Pepwave
                      2019 F350 6.7L Long Bed Crew Cab

                      Comment


                      • #12
                        Based on Jim's Ampacity chart a 60 amp charger would need 6 AWG with a 60 amp charger in the passthrough feeding the batteries. So to go with 4 AWG with the charger in close proximity to the batteries would be fine. Your original 8 AWG can be used from the passthrough to feed the camper and will be good according to the chart. This is what Jim is illustrating.

                        Another Jim

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                        • #13
                          You guys are great!!! Love this forum. Yeah I don't think, based on Jims illustration, I will overload the wire based on my needs.
                          Hopefully everything works out the way I hope. Once I am done with this upgrade I’ll post what I did just in case anyone in the future needs to use it as a guide. I am going to draw the schematic also.
                          2018 RAM 3500 Big Horn, CC SB 6.7 Cummins HO/Aisin
                          2021 GD Imagine 2800BH

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