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Thread: Charging Batteries through Cigarette Lighter

  1. #1
    Member bhollis's Avatar
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    Default Charging Batteries through Cigarette Lighter

    Recently been thinking about picking up a solar panel for the boat--maybe the kind that can be rolled up when not in use. Thinking that maybe it would allow us more time on the hook without having to start the generator to charge the house batteries.

    Here's the question. Can I simply plug the solar panel into my boat's cigarette lighter? Some of the literature on these panels indicates that will work. Can I also run the boat's 12v devices (refrigerator, stereo, etc) at the same time I've got the solar panel plugged into the cigarette lighter? Or do I need to connect the solar panel direct to the house batteries?

    Any ideas?

  2. #2
    Member JOAT's Avatar
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    Generally the lighter socket is a straight shot to the battery (through your fuse panel, of course). So if you apply a current to the lighter socket, it will go to the battery.

    The size of the solar panel will tell the rest of the story. If you're running anything off the battery while the solar panel is plugged in, the current from the solar panel will be going to the running devices. If you're drawing more than the panel puts out, it will take the rest from the battery. If you're panel is applying more current to the system than the running devices need, then the extra will go to the battery.

    Most of the small solar panels, especially those "roll up" kind, don't put out very much current. So just flipping on a few 12v light bulbs can be enough to take away all your solar capacity. They are more for low level trickle charging than anything else.
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  3. #3
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    Plugging a solar panel into a Cigarette Lighter outlet is no problem.

    A 20 watt rollup solar panel cost $400 and puts out 1.2 amp maximum, in Alaska your looking at around .6 amps. A marine dome lamp draws 10 to 20 watts. You will need several solar panels to keep up with one dome lamp on a sunny day.

  4. #4
    Member bhollis's Avatar
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    Thanks for the input. Very helpful.

    What I was hoping was that the solar panel might be able to significantly offset the power used by our boat's refrigerator--which accounts for our biggest single continuous draw of electricity. We don't use the interior lights all that much, particularly with the long days in the summer.

    The refrigerator draws around 2.5 amps when it's running, which seems to be about half of the time. Which works out to an average of somewhere around 1.25 amps/hour--24 hours a day. If you're correct that the best I could expect from a $400 solar panel in AK is around .6 amps, and probably for only 8 or so hours per day on a clear day, then I suspect you're right--probably not worth the trouble.

  5. #5
    Member jrogers's Avatar
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    The problem you would have going throught the lighter for charging would be voltage drop due to the wire gauge and possibly tripping the breaker, but neither of these would be a problem unless you have a really big solar panel. Another option might be wind. I see the sailboat guys running these little wind generators all the time but I have not looked into them, but I bet they generate a lot more power than solar.

    Jim
    Last edited by jrogers; 04-12-2009 at 23:02. Reason: clarify

  6. #6
    Member GOT TOYS's Avatar
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    Default Wind power

    I've got the 400 watt wind generator at my cabin in the Caribou Hills. It works great for helping keep my eight 100 amp-hour batteries topped off. I wouldn't put one on my boat. You will have to deal with the noise and vibration you are bound to get. I have no problem with either at my cabin because the wind generator is about 60' away and 40' up. And if you're like me, you look for coves without wind to hang out. The generator needs at least 6 mph to do anything, and ideal is about 30 mph. (I just measured 114 mph at my cabin a couple weeks ago.) Southwest Wind Power is a good place to buy off-the-grid power supplies.
    If you have the room and don't mind hauling around another 200#, I would add a couple 100 amp-hour AGM batteries to your house.
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  7. #7

    Thumbs down Need a 'sheet of plywood' sized panel

    I have the solar panel plugged into the cig lighter, it's useless and I will be removing it. It tested at next to nothing, not to mention the lack of sun in Alaska. I guess I kept thinking that as I drifted closer to Hawaii, due to dead batteries, I could eventually use it.

  8. #8

    Default Solar

    To get the maximum power per dollar consider using a hard solar panel and affixe it to the cabin roof. A hard panel costs less than half half what a roll-up panel does and is usually more effecient; Since it costs half you can buy a larger panel for the same bucks.
    Never install a solar panel UNLESS you have a blocking diode in series with the positive side wire going into the battery. Many panels have a diode in the unit lots don't. Thie diode prohibits a solar panel from draining the battery when the sun produces less power than the battery does, nearly all controllers have a blocking diode.
    Most solar panel will produce voltage at 17.5 volts and require a controller to maximize the power made. By converting the 17.5 volts into a true chargeeing 14.4 volts at the proper amperage.The controller therefor increases the chargeing amperage insuring maximumized power, even on days that your panel doesn't produce a chargeing voltage.
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  9. #9
    Moderator Paul H's Avatar
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    Your best option is a small generator, just beware of exhaust and co/co2.

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