Running a lap top efficiently?

Discussion in 'OnBoard Electronics & Controls' started by DennisRB, May 21, 2010.

  1. DennisRB
    Joined: Sep 2004
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    Location: Brisbane

    DennisRB Senior Member

    I want to run a lap top in a yacht with a limited ability to supply power on extended trips.

    Right now I can plug it into a 500W inverter which is on the verge of overloading requiring the dimming of my screen just stop the inverter shutting down. Now including the losses in the inverter this must be drawing a huge current on the order of 50A, or about 600W from the batteries. The power pack says 240V AC @ 2A.

    The thing is, on the DC side of the power pack laptop lead, the current draw is 3.16A @ 19V DC which is 60 watts, or about 10 times less than the power it is drawing from the house batteries when you include all the wasted power in the voltage conversions.

    How accurate does the 19V DC supply to the lap top have to be?

    Is there a common way of gaining efficiency here?

    DC - DC converter for 12 - 19V?

    What about 2 x 24v batteries in series regulated down to 19V?

    Should I just get a lap top that requires 24 or 12v? (if there are any)

    Should I be buy a specific laptop for this application?

    Cheers, Dennis. :)
     
  2. DennisRB
    Joined: Sep 2004
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    Location: Brisbane

    DennisRB Senior Member

    I just got a cheap car charger thing for it off ebay for $17. It has a input rating of 11-14V and a range of outputs and plugs.

    See how it goes :) I hope its efficient.
     
  3. SheetWise
    Joined: Jul 2004
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    Location: Phoenix

    SheetWise All Beach -- No Water.

    I would do a Google search for a 12v UPS for a fail-safe solution ... I know this subject came up recently and I provided a couple links. Not hard to find. Avoid application specific solutions -- this is a generic problem.
     
  4. apex1

    apex1 Guest

    That sounds like a faulty inverter. By no means can a laptop charger pull a 600W inverter down when everything is ok.
    Have you tried to connect other loads to the inverter?

    Regards
    Richard
     
  5. SheetWise
    Joined: Jul 2004
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    Location: Phoenix

    SheetWise All Beach -- No Water.

    If you're talking about the $17 eBay solution -- I agree. Again, look for a UPS which will provide a conditioned uninterrupted power supply as well as act as a buffer and storage.
     
  6. WickedGood

    WickedGood Guest

    Go get a little APC UPS system. About $150 at Sams Club, BJs Club and a 700-800 watt inverter about under $100 .

    Add a couple Deep Cycle Marine Battteries prior to the inverter and keeep them chared using your boats eniges alternator & a Solar Panal about $150



    Youll have enough power for the Laptop & A Margeritta maker for short money. Under $1,000.

    If you would like me to do the electrical work? Bring the boat to Maine . My works not cheap but qulity never is.

    WickedGoodOUtdoors@maine.rrr.com
     

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  7. SheetWise
    Joined: Jul 2004
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    Location: Phoenix

    SheetWise All Beach -- No Water.

    COMMENT: ;)

    Dutifully extended to at least five characters.
     
  8. DennisRB
    Joined: Sep 2004
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    Location: Brisbane

    DennisRB Senior Member

    Thanks for the responses guys. For now I just got this unit. It may not be the most expensive solution out there but it is designed exactly for my application of powering a laptop from 12V, so it can't be all bad?

    http://cgi.ebay.com.au/Universal-No...ccessories&hash=item335c8c139b#ht_10721wt_939

    The inverter is a an old 240 volt 500w unit that came with the boat. I said its probably drawing 600W from the battery to include losses as these things are never 100% efficient.

    In either case, using any inverter is going to waste a massive amount of power since there is a huge power loss in the laptop lead AC to DC power pack anyway. The power pack input is 240AC @ 2A which is up to 480 watts if its running at full capacity. Where the output is 19V @ 3.16A which 60w. Its no wonder the 500w inverter was struggling with 480w on it. I haven't measured these currents directly but the relationship is clear. I think this inverter is a bit suspect though.

    The inverter seems to run other items fine. I would guess its not a sine wave unit though. However I have another 300W inverter which has an even higher tendency to shut off when powering a laptop so laptops do use a lot of power when connected via the AC-DC power packs that come with them. My aim was to eliminate the AC-DC power pack to gain efficiency.

    Thanks for the offer on the work. I'm in Brisbane Australia. I'm also an electrician. :)
     
  9. marshmat
    Joined: Apr 2005
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    Location: Ontario

    marshmat Senior Member

    Inverters are never 100% efficient, but a good one should be well north of 80%. The only laptops I've ever seen that can draw more than 100 watts are those high-end four-core gaming machines. If your laptop is causing a 500W inverter to crap out, the inverter is a P.O.S. Laptops have an internal UPS in the form of their battery and its protection circuitry; add the filtering in the laptop's power supply, and there shouldn't be any problems running one on a *good* stepped-square-wave inverter.

    Let us know how your new DC/DC converter is working out.... under $20 for such a device is a hell of a deal if it actually works.
     
  10. jonr
    Joined: Sep 2008
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    Location: Great Lakes

    jonr Senior Member

    If the inverter is drawing 500+ watts and the laptop is only drawing 60, all of difference is going into heat which will be noticeable. More likely is that the inverter doesn't like the harmonic load that the laptop power supply presents. A DC/DC converter should work better. Or get a smaller, newer laptop that draws less - mine draws about 12W at 12V.
     
  11. CDK
    Joined: Aug 2007
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    Location: Adriatic sea

    CDK retired engineer

    DennisRB, the Chinese laptop charger is all you need. It is very efficient: it hardly warms up, even when switched on for hours.
    The only flaw is the set of adapter plugs included, most of them do not have the exact dimensions and make poor contact to the central pin. The Chinese who did the measuring needs reading glasses.

    I use the plug from the original AC charger. Cut the wire in half and soldered cinch plugs on the ends and one on the Chinese charger as well.
     
  12. Guest62110524

    Guest62110524 Previous Member

  13. CDK
    Joined: Aug 2007
    Posts: 3,324
    Likes: 148, Points: 63, Legacy Rep: 1819
    Location: Adriatic sea

    CDK retired engineer

  14. Guest62110524

    Guest62110524 Previous Member

    thats what I said CDK, twice as many amps 110 as 230
    God I learn from bitter exp when yacht I designed with USA systems, ran 60 amps to start the freezer compressor, single ph, was a severe test for the trace inverter which was 4000 watts spike 8ooo, once started it ran 9 amps I can nEver come to terms with WHY usa RUNS 110 60 hz
    You get a boat in any port outside NA and shore power becomes an issue
    i am zonked too tired think properly, just came back 10 weeks Germany, how are you?
     

  15. CDK
    Joined: Aug 2007
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    Location: Adriatic sea

    CDK retired engineer

    I only passed through with the camper van, mostly avoiding highways because the right hand lanes are clogged with trucks wherever you go. Turks, Bulgarians, Hungarians, Bosnians, Russians, Western Europe seems to be very popular at the moment. Pensioners like I am are better off driving "Bundesstrassen".
     
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