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can I run a laptop on a 12VDC 'car' battery?

Discussion in 'Power Electronics' started by progenator, Sep 18, 2013.

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  1. progenator


    Sep 18, 2013
    Hi, I read a few threads, mostly a few years old about running laptops from 12VDC 'car' batteries.

    Can it be done? Looks like it, but then the posts were before Li-Ion batteries were common. I understand that Li-Ion batteries have a devoted charging circuit, though this is only what goes around the grapevine?!

    Also, people on this Forum name various computers of the period that worked fine on 12VDC back in 2007. Even then, they described them as 'older computers', so please don't mind me bringing this up again.

    Googling tells me that there are LOADS of boat users who, like myself, are in need of a computer (laptop or tablet) that draws little power and runs on 12vDC without the need for either an inverter (= extra power consumption) or voltage increasers (say to 18.5VDC for many newer laptops). Both are an item extra to go wrong at sea, so a more direct approach without extra electronics is very desirable to us.

    Googling also tells me that there are no, or very few, designated 12v laptops available.

    The aim of the game is to buy 1 or even 2 or more low-spec laptops so that there is always a spare in case one gets 'washed' by accident. The computer is a valuable resource that can run loads of safety equipment on long/short handed voyages.

    So, I have a load of questions really:
    1. Is having a 'modern' Li-Ion battery a problem if one just sticks an average laptop that runs at or near 12vDC straight on to a 'car' battery? (with a fuse) or are there issues with it?
    2. Are there any laptops (specific models) available that anyone knows of that are cheap as chips but reliable, which may be suitable for the job in hand.
    3. Does anyone have any idea why it's not widely known that laptops CAN seemingly (from reading this Forum) run on 12VDC. Because other teccie sites (from the computer point of view, not from the electronics point of view) seem to jump up and down with anxiety at the very idea of trying it.
    4. Is there any advantage in charging the battery seperately rather than running the laptop with the battery in it, practically? How would one do that from a car battery to be sure it doesn't get too much charge too fast?
    5. Most batteries seem to be about 10.8 VDC (mine's 11.1VDC even on this machine wihich has a 18.5VDC output powerpack!). Why is the voltage so different and can I therefore run this machine from a 12VDC battery? Do I need a 'smoother' or controller or the like? Please note that this machine has a 3rd pin in the charger and supposedly uses intelligent charging, whatever that is. Is that a gimmick or does it have real application and does it make any difference to running on 12vdc?

    I know I'm new here and have loads of questions, so please forgive me, there seems to be so much taboo about this, so I am really trying to get to the bottom of it in one fell swoop and hopefully good answers will be able to help loads of other boat (etc.) users.

  2. goldfist


    Sep 18, 2013
    Yes it can be done however I would use an inverter to turn the 12VDC to 120VAC and use the power supply intended for the computer. You can get an inverter to run a laptop for around $20. I have a 750 watt peak, 350 watt continuous that I use during power outages with a 12VDC 750 CA car battery, but I need to upgrade to more watts.

    A car battery is actually a poor choice though for continuous use as for a Marine Deep Cycle Battery is best for charging and draining. Car batteries are only really intended for a quick amperage burst to turn the engine over and start the field in the alternator to generate electricity greater than the draw of all accessories when the engine then spins the alternator.

    To avoid frying your laptop, I would get an inverter and plug the laptops external DC power supply to the outlet on the inverter.This inverterw will take 12VDC and make 120VAC, and then the power supply intended for the laptop will then take the 120VAC and make the 18.5VDC
    Last edited: Sep 19, 2013
  3. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
    I would actually look to see if something like an IPad would do the jobs required.

    There are 12V chargers available for these, and they are small, light, and cheap enough to have some spares.

    In addition you may be able to get some sort of bag to seal your ipad in so that it will be safe from splashes (but possibly not total immersion).

    Other than that, I have an old Acer eebox that runs directly from 12V, but you need 240V to run the monitor.

    I'll try to get back to you on some of the other questions later if nobody else does...
  4. Deigh


    Apr 26, 2011
    I've just purchased a Samsung computer which is 12v. I have ordered a cigarette lighter plug-in device on the internet which should run it. Unfortunately it is coming from Australia and hasn't arrived yet. I have tried several inverters but they do not work with the existing battery setup in the computer. Up till now I have had to rely on the battery's memory to get me through the times when I'm freedom camping and there is no 240v available:D

    Will let you know how successful it is when it is to hand.
    Last edited by a moderator: Sep 20, 2013
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