Help/Ideas Dual 12v Batteries

Discussion in 'Power - Site Power/Batteries/Generators/Solar' started by ColoradoChris, Jul 14, 2019.

  1. ColoradoChris

    ColoradoChris New Member

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    Hello all! Please forgive me if this topic is covered elsewhere, but after much searching I was unable to find the information I am looking for. I’d like to hear from people who have done this on their own and didnt have wiring in place from the dealer/factory.

    Background:
    -2019 Rockwood 1640esp
    -Currently using a small gas/propane generator for camp charging
    -Looking to get solar in the near future and use generator for backup charging.

    -2 identical batteries were supplied by the dealer

    Question:
    Can anyone help me with adding a second 12v battery to my system. Are there safety/charging concerns?

    -I would like to add a second battery to the system to increase our capacity while boondocking.

    -I’d like to have a system that still charges off the 7pin while driving (I’ve read where that can be bad for batteries though)

    -Is it as simple as wiring in a second battery?

    -Are voltage regulators necessary?

    -Any extra fuses?

    -Did you bypass the factory charging system? If so why and what did you use?

    Thanks in advance for all your replies!

    P.S. I’m not lazy... I have a 2yo and would rather not design a system from scratch.
     
    Last edited: Jul 14, 2019
  2. rabird

    rabird Howdy!

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    yes, adding a 2nd 12v batt you wire them in a balanced fashion (in parallel, + to + & - to -) with the + & - (load & charge) wires coming off different batteries. 2 x 12v in parallel makes one big 12v.

    Pianotuna12V.png
     
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  3. tombiasi

    tombiasi Well-Known Member

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    Please keep in mind that to use the configuration shown above the batteries need to be the same chemistry, same capacity, and preferably at the same state of charge.
     
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  4. SteveP

    SteveP Well-Known Member

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    Read The 12 volt side of Life

    Get another battery as close to the same as your current battery as possible, same group size, capacity, brand and model. Connect the two in parallel, positive on bat 1 to positive on bat 2, negative on bat 1 to negative on bat 2. Use actual battery cables instead of wire to connect the two.

    Connect the house positive for the camper to the positive on bat 1 and the ground to frame to the negative on bat 2.
    Not at all, anything that helps maintain the charge on the battery is a plus, just don't expect this to work as a charging solution, just as a helper.

    No extra fuses, nothing you need to disconnect.

    IMO you should also have a good 10 amp or better 3 stage stand alone charger and make sure your batteries are fully charged just before and immediately after camping.

    Disconnect the ground to frame from the bat 2 negative post when the camper is in storage mode to prevent parasitic draws from the camper from discharging the battery.
     
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  5. rabird

    rabird Howdy!

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    A different approach would be 2 new 6v golf car batteries, hooking them is series to make a big 12v.
    GC batteries are generally more robust for cycling over and over and ~ the same price as a 12v.
     
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  6. tenttrailer

    tenttrailer Art & Joyce - Columbus, O

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    We did two 12v G-31 batteries giving us a total of 210 AH. Only thing we needed to do was change the battery box, add a second battery box and add the 2 wires mentioned above in the diagram. We used #6 copper wire to tie them together. All the rest of the wiring we left alone including running both ground and positive wires to the location of the original battery. Not an issue with #6 wire between the 2 batteries.

    We are good for 4-5 days and nights running the furnace in 20-30 degree weather and keeping the temperature at 68. After 4 days we are right at about 12.2-3V

    Just added 160W semi flexible solar panel on the roof. Laying flat on the roof it is equal to about 120W. I'm thinking one good sunny day out of 4 days we should be good for as long that we want to camp in the winter. Also, I belive on a sunny day I should be able to supply almost all the power need for the 12V fridge when traveling.
     
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  7. Anthony Hitchings

    Anthony Hitchings Active Member

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    and perhaps be the same age as well
     
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  8. tombiasi

    tombiasi Well-Known Member

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    Can't hurt
     
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  9. ColoradoChris

    ColoradoChris New Member

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    Both batteries are identical from the dealer.

    So I should use actual battery cables between the 2 batteries (only?) but I can use the 4-6 gauge wire to the frame/ground and to the camper connection?
     
  10. SteveP

    SteveP Well-Known Member

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    Use the existing wires for connection to the camper and the frame/ground. The larger battery cables between the 2 batteries will help even the flow between the batteries.
     
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  11. rabird

    rabird Howdy!

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    http://www.smartgauge.co.uk/batt_con.html(connecting batts - parrallel)
    "Finally, if you only have 2 batteries, then simply linking them together and taking the main feeds from diagonally opposite corners cannot be improved upon.

    And finally, finally, we keep getting asked where the chargers should be connected to. We didn't address this question because it seemed so blatantly obvious where they should be connected that it never occurred to us that anyone might be unsure. The chargers should always be connected to the same points as the loads. Without exception. "

    here's why!
     
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  12. hq308

    hq308 Active Member

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    To charge off the TV while traveling look into fitting a DC/DC charger to the trailer
     
  13. Anthony Hitchings

    Anthony Hitchings Active Member

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    if you mean the new option, such as the Renogy (which I just bought, for a different reason), it also needs a 12V control voltage from a switched source (as well as connecting between the TV battery and the 7-pin socket).
     
  14. Anthony Hitchings

    Anthony Hitchings Active Member

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    6AWG wire may be a bit of a fight if we are talking interior separate battery boxes. 10AWG would be OK for this application (light loads, short wire run, low charging rates). If batteries are going to be wired up in a common exterior battery box then heavier gage wire will route OK.
     
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  15. ColoradoChris

    ColoradoChris New Member

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    Thanks for the info. I’m actually using 2 separate boxes mounted next to each other. I picked up some 4ga battery-to-starter wires from the auto parts store yesterday. Maybe I’ll get a chance to wire everything up in the next week or two.
     
  16. hq308

    hq308 Active Member

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    Not familiar with Renogy but a quick Google search indicates it's something to do with solar? A DC/DC charger is installed near the trailer batteries and boosts the voltage from the TV to a suitable voltage to get the camper batteries fully charged. The voltage from the TV drops by the time it gets to the trailer so without a DC/DC charger the TV can never fully charge the camper batteries. The below link is a premium supplier of DC/DC chargers that will give you a bit of an idea what they are about.

    https://www.redarc.com.au/battery-chargers/in-vehicle-chargers
     

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