Dual Power TV

Discussion in 'Electronics Q&A' started by bobeast, Feb 19, 2018.

  1. bobeast

    bobeast Dance the Tide SILVER Sponsor

    520
    Oct 22, 2017
    Isleton, CA
    2002 310DA
    350 MPI w/V-drives
    I know some of you have installed a 12VDC TV so you can watch on the hook. It occurred to me, that if you are hooked to shore power or running the gen, you might prefer to have the TV run off of that instead. Our fridges are smart enough to switch over to AC when we plug in, so I figured there must be a way add the same functionality to my TV.

    I don't know how many folks around here can read a schematic, but here's an auto-power circuit I cooked up. Screen Shot 2018-02-19 at 3.43.31 PM.png
    The relay has normally closed contacts which means when shore or gen power is applied, the contacts open up. This disconnects the 12vdc lighter socket from the house bank. At the same time, the wall-wart gets 120vac from shore or gen and supplies +12V to the TV.

    When shore power is removed, the relay contacts close, supplying +12vdc from the house bank to the lighter socket. The diode isolates house power from the wall wart.

    Note, this same kind of setup can be used for other 12v devices, such as a DVD player, DVR, etc. Just make up multiple DC harnesses and and use a multi-outlet lighter socket.
     
  2. Mittens

    Mittens Active Member

    461
    Mar 5, 2017
    Huntsville, AL
    2002 340 Sundancer, All Cherry Cabin, Black Canvas.
    8.1 Mercs, V Drives, 4.5kw Westerbeke.
    Sure would love a box I could feed it 12v, and 110 and it do it all....
     
  3. KevinC

    KevinC Well-Known Member

    Feb 25, 2011
    Long Island, NY
    2004 340 Sundancer
    1988 Proline Center Console - 90hp Mariner/Mercury
    1969 Boston Whaler
    Twin 8.1 V-drives
    Quick question. Why would this scenario be better than going with a straight DC powered TV? I am not try to diminish your solution just wondering if I am overlooking something or if yours would be a better path.

    Personally, I am looking to add a 32" TV and I am planning on using a step-voltage regulator to go 12V->19V to feed the TV. This would eliminate the need to switch power depending on if we are on shore power or generator and would also provide a regulated voltage while feeding from battery/alternator. It would also give me a single power path.

    If I am on shore power or generator then I would be charging my batteries anyway.

    -Kevin
     
  4. bobeast

    bobeast Dance the Tide SILVER Sponsor

    520
    Oct 22, 2017
    Isleton, CA
    2002 310DA
    350 MPI w/V-drives
    Kevin. Good question. I think the main issue is that anything you run off of DC when you are on shore power, steals charge-current from your charger. I'd rather run as much as I can on AC when I'm plugged in or running the gen so the full benefit of my charger is applied to replenishing my batteries. In my case, I have a TV, a BlueRay Player and a TiVo, and they add up.
     
  5. 370Dancer

    370Dancer Member

    696
    Oct 2, 2006
    Florida - Alabama
    1998 370 Sundancer
    380hp MAG MPI V drives
    bobeast comment aside, I'd just use today's inverters, and run them off of 12v even when on shore power. That gets you full time power, so no drops when switching power sources. I run a 3.4 cu refrigerator that way, and am about to add an inverter to the entertainment group for the same reason. full disclosure, we are hardly ever just on 12v without an engine running. No campers in my entourage.
     
  6. bobeast

    bobeast Dance the Tide SILVER Sponsor

    520
    Oct 22, 2017
    Isleton, CA
    2002 310DA
    350 MPI w/V-drives
    Yeah. that can work if you are not one to run your batteries to within an inch of their life. I thought about the inverter route, but for me the math didn't work out.
     
  7. KevinC

    KevinC Well-Known Member

    Feb 25, 2011
    Long Island, NY
    2004 340 Sundancer
    1988 Proline Center Console - 90hp Mariner/Mercury
    1969 Boston Whaler
    Twin 8.1 V-drives
    Personally I would prefer to get a TV with DC input and skip the inverter. A regulator would keep the voltage steady and since most TVs are DC internally today why go ac-dc-ac-dc instead of ac-dc which is more efficient.

    -Kevin
     

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