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Laptop powered via cigarette lighter?

Discussion in 'LEDs and Optoelectronics' started by Rsmo, Aug 24, 2011.

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  1. Rsmo

    Rsmo

    6
    0
    Jul 22, 2011
    Hi,

    I have a power inverter, about 300 watts, that I use with my car's cigarette lighter to power my cell phone charger.

    I have a Laptop that uses about 60 watts, maybe 75 at peak power.

    Do you guys think my cigarette lighter can safely power the laptop without blowing a fuse?

    Thanks
     
  2. davelectronic

    davelectronic

    1,087
    12
    Dec 13, 2010
    lighter socket power

    Hi there.
    Don't see why not, use the correct fuse for the laptops power, the fuse in the lighters plug, laptop power in watts, divided by its supply voltage, and thats your fuse, 20mm i expect, choose a quick blow type, 500ma above the laptops power should be ok, peak that is. Dave. :) PS the lighters plug top normally unscrews, your find the fuse in there, choose a fuse to match the laptops power requirements.
     
    Last edited: Aug 25, 2011
  3. Resqueline

    Resqueline

    2,848
    2
    Jul 31, 2009
    Car cig. lighters draw approx. 4A (50W) meaning the car fuse & wiring is at least 8A, most likely 10 or 15A, so you can safely draw at least 100W from it.
    How well the inverter behaves with the added load (& hence some extra voltage drop) is another matter. Just try it out, it won't blow anything.
     
  4. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,497
    2,839
    Jan 21, 2010
    Well, maybe.

    I blew the fuse in the car when I was running my laptop from the cigarette lighter.

    It was fine until we stopped and I was running on battery for a while. The additional load to power the laptop *and* charge the battery was too much.
     
  5. poor mystic

    poor mystic

    1,074
    33
    Apr 8, 2011
    So was there a brown-out, where voltage fell, and the inverter began to draw a lot of current? I'm wondering which fuse blew?
     
  6. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,497
    2,839
    Jan 21, 2010
    Car running, laptop battery charged. Inverter supplies power to laptop -- All OK

    Car stops. No power to inverter. Laptop battery supplies power -- All OK

    Car starts. Power to inverter. Inverter supplies power to run laptop *and* charge laptop battery. Car fuse to cigarette lighter blows.

    Moral of the story is that a laptop draws significantly more power while charging its battery (which is kinda obvious, but...)
     
  7. Rsmo

    Rsmo

    6
    0
    Jul 22, 2011
    I finally tried this today. The inverter made a loud, continuous beeping noise and shut off power to the laptop, so that tells me the laptop was drawing too much power.

    I made 100% sure the laptop's battery was fully charged due to what you guys said.

    So now that I know the cigarette lighter is not an option I am getting an inverter that can draw power from the battery terminals of the car.

    This is the one I'm getting:

    http://www.walmart.com/ip/XO-Vision-600W-DC-to-AC-Power-Inverter/15779978
     
  8. Resqueline

    Resqueline

    2,848
    2
    Jul 31, 2009
    Connecting the inverter to the car before or after connecting the laptop PSU may give different results. I've seen some of them being a little tricky in getting started.

    I'd rather buy a 12V to 19V inverter supplying the laptop directly with just one unit, to avoid the complex, bulky & inefficient step via mains voltage.
    Unless you need the mains & USB outlets for other purposes too of course.

    Steve, do you remember how big that car fuse was? Did you notice if it blew when you turned the ignition on or when the engine started? Could the car starting have defeated some soft-start function in the inverter?
    Some cars supply the cig lighter independently of ignition and some shut it off with ignition.
     
  9. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,497
    2,839
    Jan 21, 2010
    It was quite a while ago.

    As I recall, the fuse blew a short while after the car was started again. It was a "slight overload" failure rather than a sudden gross overload.

    I think it was a 10A fuse. The same circuit also powered a number of other accessories (which is what made me less popular)
     
  10. sktan

    sktan

    3
    0
    Feb 27, 2015
    Got a picture?
     
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