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Shore power w battery removed?

JennyMJennyM Member Posts: 1
in Battery/Electrical & Solar
If I take the 12 V marine battery out to replace it w a new one can I leave my TAB 320s plugged in to shore power for the peripherals?
many thanks!
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Comments

  • westernstateswesternstates Member Posts: 15
    I had my battery switch off today when I was hooking up my truck.
    I noticed the lights were working so I now know that the Tab gets power from the truck even with the battery switch off.
    I know this doesn’t answer your question but now I have one more thing I want to also find out.
    I wonder if the battery charger pushes 12 volts directly to the system regardless of the battery.
    2021 T@B 400
    2021 Ford F150 2.7 turbo
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  • pthomas745pthomas745 Administrator, Moderator Posts: 4,473
    edited 5:41AM
    @JennyM The "converter". when on shore power, distributes power to the 120V and the 12V items in the trailer, even with no battery in the trailer, or when the battery switch is off.  With the battery switch off, the converter will not charge the battery.  If you have installed solar, the solar setups are wired directly to the battery, so solar will always charge the battery when the sun is on the panel and the battery needs charging.  When towing the trailer: you need a battery installed, with the battery disconnect switch on.  The trailer's "emergency break away brakes" are powered from the trailer's battery, so the switch needs to be on.
    Welcome to the Forums!

    @westernstates I think you are asking the same basic question: if there is no battery in the trailer, or the battery switch is off, the WFCO will distribute power to the 12V items in the trailer.
    What you discovered with the "12V working in the trailer with the tow vehicle connected and the battery switch off" is that you do have a "charge line" from your tow vehicle battery to the trailer's WFCO.  That doesn't necessarily mean that your tow vehicle can actually charge the battery successfully, due to a lot of different factors.  What you should check for, however, is what happens when you turn off the tow vehicle ignition.  If the lights in the trailer stay on with the 7 pin connected and the ignition switch off, that would mean that if the trailer battery switch was on, the two batteries would be connected together....and the two batteries will begin to "balance each other out".  The problem would be the tow vehicle battery being drawn down to a state of charge that might not start the tow vehicle engine.  
    This question comes up when owners ask about "do I have to unplug the trailer from the tow vehicle when I'm parked?"  "Back in the day", the problem of a tow vehicle battery being drawn down from a trailer battery was apparently pretty common.  In modern vehicles, with so many battery hungry devices, many vehicles now have "isolation relays" that prevents any draw from the vehicle battery when attached to the trailer.  
    So, you need to work on one more test to "know" what might happen with your tow vehicle connected.  The thread below explains this in a clearer way (I think!) and it includes a short test to determine if your vehicle has an "isolation relay".
    Find Mousketab's comment in this thread.
     PS:  Some owners have made "7 pin plug adapters" to use the 7 pin to add extra battery power, or attach a solar controller to charge the battery.  When I use my "adapter" with my "spare" battery, I leave the battery switch off, and my "spare" runs the trailer. When I want to charge the trailer battery through the 7 pin, I leave the battery switch on.
    2017 Outback
    Towed by 2014 Touareg TDi
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  • ScottGScottG Administrator Posts: 5,643
    Yes. (But I suggest UNPLUGGING shore power when disconnecting or reconnecting a battery.)

    Also, note that if you tow without a battery, your emergency breakaways brakes will not function in the event of a total trailer separation.
    2015 T@B Max S (320)
    2015 Nissan Frontier SV V6 4x4
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  • HoriganHorigan Member Posts: 838
    In addition to unplugging shore power while disconnecting, if you have solar, those battery leads will be hot, so tape over the positive wire terminal so you don't short out your solar controller.  Have the battery switch off so you don't risk shorting the converter.
    Rich
    2019 T@b 400
    2025 Toyota Highlander 2.4L Turbo
    Bellingham WA
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