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Charging a deep cycle battery from cigarette lighter socket

  1. May 13, 2008 #1
    I'd just like some advice on how best to charge a 70 amp hour deep cycle battery from a cigarette lighter socket. I use the battery to run my 35 litre waeco fridge when I'm camping for a couple of days, but would then like to charge the battery while travelling. I'm guessing a flat 70AHr battery will draw too much current from the car's circuit. Is there a current regulating device available for this purpose? My car has no room for a full RV style dual battery system.
    Thanks in advance,
    Ian. S.
  2. jcsd
  3. May 13, 2008 #2


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    Welcome to PF, Ian.
    My first step would be to check the fuse panel and see what the rating for the lighter socket is. In any vehicle that I've owned, the lighter was on a circuit all to itself.
  4. May 13, 2008 #3


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    Maybe you should just buy a lighter-plug trickle charger.
  5. May 13, 2008 #4


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    Yes, a flat battery that size is going to draw too much current to plug directly in the cigarette lighter socket.
    The other issue is that you don't want the battery in the passenger area.
    There is always the possibility of explosion from accumulated gasses vented off in charging.

    Another problem is that if you use current limiting then it's going to take a very long drive to charge it up.
    A minimum of 8 hours with the 10A limit of most cigarette lighter sockets.
    You took 70amp hours out with the fridge. You gotta put at least that much back in.

    You might want to reconsider the RV type dual charger.
    The dual diode setup is very small, so all you really need is a place to put the battery while you're driving to charge it.
    The dual diode setup doesn't require the 2nd battery to be in place so you can take the battery out if you want without removing the circuitry.
    It's still going to take an hour or two of driving to give it a fair charge.

    You might want to check out some car audio places doing high power amps.
    I suspect some will have experience and the necessary hardware to set this up for you.
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