Second battery into solar port

MikeDawn265
MikeDawn265 Member Posts: 29
in Battery/Electrical & Solar
Can I plug a second battery into the SAE solar port for auxiliary power if my T@B battery is low? I have a 100 watt Renogy suitcase solar, but I'm in for some cold/cloudy weather on my trip and am concerned about power. I have the polarity adapter for my port.
Wisconsinites 2020 T@B 320 S - 2021 Dodge Durango GT Plus TV
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Comments

  • ScottG
    ScottG Administrator Posts: 5,655
    Assuming your SAE port is wired like mine, doing would be effectively hooking up the two batteries in parallel. This is done frequently as a way to increase battery capacity, and I think it has been discussed here in the past. However, if the two batteries are at different states of charge, they will tend to equalize each other. This may reduce your efficiency somewhat, but to what practical degree is beyond my knowledge. Maybe someone else with actual experience can elaborate.

    Another issue is to make absolute certain that you have the polarity correct, since there is no standard as to which pin carries which leg (+ or -) of the circuit. You are obviously thinking of this since you mentioned an adapter. In any case, be sure to verify the polarity yourself (either visually or by checking continuity) before hooking anything up!
    2015 T@B Max S (320)
    2015 Nissan Frontier SV V6 4x4
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  • Sharon_is_SAM
    Sharon_is_SAM Member Posts: 10,061
    Not sure about this, but are the solar port wires large enough to draw power from a secondary battery without heating up?
    Sharon / 2017 T@B CSS / 2015 Toyota Sienna Minivan / Westlake, Ohio
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  • MarkAl
    MarkAl Member Posts: 509
    I'd replace the existing trailer battery first. To parallel the batteries as ScottG said will to some degree use the fresh battery's energy to recharge the depleted one and then have a smaller amount available for the trailer's need. Ultimately you won't win in this case. It's okay if both are fully charged, but even then with wire losses of the long run the batteries will not work well together, unlike when they have short wires doing it in close proximity....
    Snohomish WA, 2015 Diesel Grand Cherokee
    Sm@ll World: 2021 320S Boondock, 6V Pb-acid
    Shunt, Roof & Remote solar & 30A DC-DC Chargers
    managed by VE Smart Network
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  • ScottG
    ScottG Administrator Posts: 5,655
    Sharon_is_SAM said:
    Not sure about this, but are the solar port wires large enough to draw power from a secondary battery without heating up?
    IIRC, mine were 10g--large enough for the T@Bs 30A maximum draw.
    2015 T@B Max S (320)
    2015 Nissan Frontier SV V6 4x4
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  • pthomas745
    pthomas745 Administrator, Moderator Posts: 4,542
    I just looked this up a minute ago.....

    2017 Outback
    Towed by 2014 Touareg TDi
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  • ScottG
    ScottG Administrator Posts: 5,655
    Ha ha. That's the discussion I was thinking of! I forgot it was one I had started...  :-/
    2015 T@B Max S (320)
    2015 Nissan Frontier SV V6 4x4
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  • MikeDawn265
    MikeDawn265 Member Posts: 29
    I'll keep ya'll posted on this.
    I leave tomorrow morning for a 10 day, 3 location trip, the first 7 days are non electric. I hope it will not be necessary to do this  :)
    Wisconsinites 2020 T@B 320 S - 2021 Dodge Durango GT Plus TV
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  • ScottG
    ScottG Administrator Posts: 5,655
    Experience is the best teacher. Good luck!
    2015 T@B Max S (320)
    2015 Nissan Frontier SV V6 4x4
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  • MarkAl
    MarkAl Member Posts: 509
    Hadn't thought about that, just unbolt the negative terminal on the trailer battery and connect your spare to the solar port (verify the polarity before you connect it!).
    Snohomish WA, 2015 Diesel Grand Cherokee
    Sm@ll World: 2021 320S Boondock, 6V Pb-acid
    Shunt, Roof & Remote solar & 30A DC-DC Chargers
    managed by VE Smart Network
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  • pthomas745
    pthomas745 Administrator, Moderator Posts: 4,542
    I've figured out my "solar port", checked it with a multimeter  I've rewired SAE cables to have a 12V plug coming from the port.  With a small inverter plugged into the 12v plug,   I've realized there are many things the port can be used for:  running lights around the trailer, power to those little digital antennas, using the little plug in voltmeters for battery monitoring...... It can be a great accessory plug if you think the connections through.
    2017 Outback
    Towed by 2014 Touareg TDi
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  • Denny16
    Denny16 Member Posts: 5,431
    That works, if the port is connected directly to the battery circuit.  If their is a solar controller between the port and battery than you can only use it for solar panel connections.
    cheers
    2018 TaB400 Custom Boondock,  Jeep Gladiator truck, Northern California Coast.
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  • Sharon_is_SAM
    Sharon_is_SAM Member Posts: 10,061
    Just confirmed with Creed that the solar port wires are 10 gauge.
    Sharon / 2017 T@B CSS / 2015 Toyota Sienna Minivan / Westlake, Ohio
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  • Denny16
    Denny16 Member Posts: 5,431
    edited September 2020
    Grand, than the wires can carry the current OK, as long as you are not running a larger inverter, or other heavy load source.
    cheers
    2018 TaB400 Custom Boondock,  Jeep Gladiator truck, Northern California Coast.
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