Using 12v System to Directly Power Computers and other DC Eq.

Discussion in 'OnBoard Electronics & Controls' started by JPC, Nov 1, 2006.

  1. Hank Rosendal
    Joined: Oct 2006
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    Location: West Australia

    Hank Rosendal not old enough for some things, too old for others

    I think "Marchmat" hinted earlier on, why not stick to the mains (110/220/240) voltage with an (DC/AC) inverter? It means a lot less boxes and converters of many kinds, it remains flexible for future equipment. By all means, use the 12 Volt battery power for the equipment which uses that Voltage, otherwise use the DC/AC inverter. I have used normal (non-marinised) desktop computers on my yacht for 10 years, none have 'rusted out'. I only upgraded them to keep up with the speed. Right now I have a Shuttle: fast, small and virtullay silent.
    The only drawback is that the bigger (LCD) screens, we love for the charts, are also the ones which use most of the power.
     
  2. Tim B
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    Location: Southern England

    Tim B Senior Member

    Because converting from 12 volts to 240 wastes power if there's no need to do it. and when on a boat, power is the second biggest electronic problem you'd rather not have.

    Tim B.
     
  3. SeaSpark
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    Location: Holland

    SeaSpark -

    240 volts

    I know it is common practice nowadays but i still think installing any 240 equipment on a yacht is ridiculous if only for the watery environment.
     
  4. TerryKing
    Joined: Feb 2007
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    TerryKing On The Water SOON

    "Boat"Size/Electrical power

    Boats are unusual in that there is such a range of sizes. Smaller boats can run everything on 12V, and I'd personally want everything "important" for safety to be 12V. But at the high end, you need higher voltage to run the little extras like the A/C,the freezer and the system that runs the buttons you push to call the steward. And 220 volts and 50Hz is approaching a worldwide common 'standard'.
     
  5. alan white
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    Location: maine

    alan white Senior Member

    We won't ever give up our 120 volts or our extra ten cycles, Terry. We need them in case of terrorists attacking our appliances. They don't know how to hook up their dastardly timing devices to them.
    Our president, by the way, has as much as said that one day the whole world will be set up for 120v at 60 hz. Even if we have to go in and do it ourselves.

    A.
     
  6. TerryKing
    Joined: Feb 2007
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    Location: Topsham, Vermont

    TerryKing On The Water SOON

    His pronouncements on subjects in which he has little apparent expertise are having less and less effect every day. Even in Washington.

    However,I've been back in the USA for less than 24 hours, and my brain may not yet be phase locked to the predominate signals...
     
  7. alan white
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    Location: maine

    alan white Senior Member

    No hurry. Enjoy that lovely weather. A bit cold tonight--- perfect sleeping weather. That is, if you're back in Vermont?

    A.
     
  8. Frosty

    Frosty Previous Member

    Proper boats dont have salt water inside of them. 240 volts is a very sensible way to go.

    The only 12 volt stuff I have on board is the nasty marine crap that I have to buy because its not available in 240 --toilets.

    Power or sailing have different opinions on this. I understand different expectations of power consumption.

    With engines running ( and I have to- to move) I have 2.5 KW invertor wired to the ring main.


    2 fridges 80 watts and an entire kitchen with rice cooker and micro wave is usable-- (with deviation in mind).

    Fans and lap top load is minimal and is almost un-measurable.

    Most boats spend 80 % or more in a Marina. Why not wire it up for such use.
     
  9. SeaSpark
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    SeaSpark -

    Proper yachts

    Proper yachts with engines running all the time do not exist in my vocabulary :)
     
  10. Portager
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    Location: Southern California

    Portager Senior Member

    This discussion is bordering on becoming ridiculous.

    It is more efficient to power DC loads off DC power even if you need a DC to DC converter. It is absurd to convert DC power to AC with an inverter to power an AC power supply which produces DC power to run a computer. If you want to count boxes then DC wins two to one, unless you don't count the inverter and the power supply inside the PC.
     
  11. StianM
    Joined: May 2006
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    StianM Senior Member

    That is exstremly funny:D It would actualy be perfect if US switched to 230V while Europe switched to 60Hz.

    Higer voltage make the machines smaler while higher frequensy enable you to use less iron in transformers.

    I think a DC to AC inverter make more sence since you might want to use the AC power to other things than just laptops running 12VDC. Maybe you have a cellphone charger running 9VDC. Or maybe the wife just have to bring hear hair dryer;)
     
  12. Tim B
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    Tim B Senior Member

    There are certain cases (primarily hairdryers) where 240V AC is handy (I have an inverter so I don't double the kit I have) but remember that this thread is primarily about computers, and lately about on-board (ie. built-in or embedded) computers 240VAC is just wasting energy at that point.

    As for standard power, 240 volts, frequency wouldn't really matter between 50 and 60 Hz would it?

    Tim B.
     
  13. StianM
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    StianM Senior Member

    Converting 12VDC to 240VAC and back wont cost that mutch energy, probertly less than a candle produce. Even if you at the moment only think about computers there will allways be a time when 240VAC turns out to come in handy. For 12VDC for computer use I would be suprised if there is not posible to buy car chargers for nootbooks.:confused:

    50 and 60 is really only interesting in transformers since a increase in Hz will lower the nead for iron and therfor making the transformer lighter. Not really off anny practical interest.
     
  14. Portager
    Joined: May 2002
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    Portager Senior Member

    As I said, "It is more efficient to power DC loads off DC power even if you need a DC to DC converter." The hair dryer is an AC load and therefore falls outside this statement. Most cell phones offer a car adapter which runs off 12/24 VDC power and this is basically a DC/DC converter that converts 12/24 VDC to the voltage that the cell phone requires. Typical power conversion efficiency of these devices is in the 90% to 93% range. Inverters convert DC power to AC power and they can achieve 90% to 96% efficiency, however when lightly loaded their efficiency drops to 80% to 85%. For an AC to DC power supply, assuming it is specially designed for the load, can have an efficiency of up to 95% but typically it will be 85% to 90% (especially for low cost consumer grade power supplies). Taking the produce of the lightly loaded inverter efficiency and the consumer grade power supply efficiency yields an overall efficiency of 68% to 80% while a dedicated inverter and high quality power supply will range between 85% and 91%. Note the general purpose inverter and consumer grade power supply is far less efficient than the DC/DC converter. Only a dedicated inverter and a high quality power supply can come close to the efficiency of a DC/DC converter. This equates to longer running time on the battery bank and less waste heat in the cabin and it proves my point.
     

  15. StianM
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    StianM Senior Member

    I don't understand why you bring up this efficensy problem:confused:

    The DC converter for my computer has a output of 4,74A(at both 100 and 240V). So even a efficensy off 50% would mean nothing. The power lost is so minimal that it's not interesting.

    Cell phones nead 9V, Computers nead 12V so I just don't understand why annyone would not want a AC inverter instead and get more freedom in what equitment they can use.

    I know what I would do, but everone have to find out what make sence to them.
     
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