running a generator with my own boat motor ??? Please read and give me some ideas!

Discussion in 'Electrical Systems' started by clctrader, Jun 15, 2010.

  1. clctrader
    Joined: May 2006
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    clctrader Junior Member

    I currently have a Luhrs 25' Pilothouse powered by a Perkins 240HP turbo diesel. I dont have space for a generator after I remodeled the boat.

    Is there any way that I could buy a generator motor, (just the elect. generating motor) and drive it using the crankshaft of my current diesel engine to produce electricity? That way I wont have to give up one of my livewells???

    If anyone has seen this done before or have any ideas, please help me out...
     
  2. WestVanHan
    Joined: Aug 2009
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    WestVanHan Not a Senior Member

    Mount another alternator or two (up to 350 amps each)...sized according to battery capacity
     
  3. CDK
    Joined: Aug 2007
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    CDK retired engineer

    What is the purpose of the generator and how much electrical power do you need?
     
  4. capt littlelegs
    Joined: Apr 2010
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    capt littlelegs New Member

    That's a big lump to run an AC alternator and although possible there will be issues of a fixed alternator speed and engine speed control to overcome. Not the most efficient or practical way to do it. Another way is to fit a large DC alternator or maybe your existing will do for charging batteries and powering a suitable inverter if you need AC power and a sufficiently sized battery for quiet running. How big these things are depends on what power you need.
     
  5. kapnD
    Joined: Jan 2003
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    kapnD Senior Member

    You first need to figure out how much power you need.
    On a 25' pilothouse, it cant be much unless you are running heavy commercial gear and refrigeration.
    Changing out the alternator to a high output unit and running an inverter is probably your best bet.
     
  6. apex1

    apex1 Guest

    Yepp,

    thats the "cheap trick". Stick with DC and a proper sized alternator***, then let "Victronenergy" do the rest for you. (stay away from cheap inverters)

    Regards
    Richard

    ***http://www.zena.net/htdocs/alternators/mar_alt.shtml#Top
     
  7. erik818
    Joined: Feb 2007
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    erik818 Senior Member

    Once we solved a similar problem for a land vehicle in my company. There wasn't enough space around the engine to mount the generator in the normal location. We solved it by using a hydraulic transmission from the engine power shaft to the generator. This way we were free to locate the generator where there was an empty volume in the vehicle.

    Another positive effect was that the hydraulic transmission allowed us to run the generator at the best speed regardless of engine speed. The generator could charge with maximum current also with the engine almost at idle speed.

    Erik
     
  8. tunnels

    tunnels Previous Member

    This is the best and logical answer i have seen for a long time !Well done
    :)
     
  9. apex1

    apex1 Guest

    Hmm,

    I dare to contradict.

    Though possible, it is rather expensive, noisy and inefficient.

    The alternator replacement is by far the easiest solution!

    Regards
    Richard
     
  10. CDK
    Joined: Aug 2007
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    CDK retired engineer

    Clctrader hasn't responded yet, but I think he needs a generator that provides him with 110 V. 60 Hz. Because a constant rpm of 3600 or 1800 would be necessary, mechanical power take-off from an engine with variable rpm is no option unless a cvt is used. That is possible, efficient but expensive, so only worth thinking about if the power demand is considerable, say 5 Kw or more.

    Hydraulics at the rpm needed have poor efficiency, I estimate around 60%. Multiplied by the generator's 80%, the overall value will be 48%.

    Or in other words 1 hp will generate a modest 350 Watts......Plus noise and excess heat.

    A belt driven alternator with a solid state inverter is the cost effective solution. I believe there are even alternators where the inverter is integrated.
     
  11. apex1

    apex1 Guest

    What I say................
     
  12. erik818
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    erik818 Senior Member

    I support the idea to use the main engine instead of a separate diesel generator, provided that the main engine has no problems with running on idle for long times. One system less to maintain.

    I don't really think that the lower efficiency with hydraulics + AC generator compared to DC generator + inverter is a great issue considering a 240HP engine is running on low rpm to provide the power.

    I see no point in arguing that the hydraulics solution should be used if a larger DC generator + inverter will do the same work for a lower cost and with less complexity. A hydraulic transmission is a possibility to consider if there isn't a better solution given the restraints in this particular case.

    Erik
     
  13. apex1

    apex1 Guest

    Concur........:)
     
  14. Typhoon
    Joined: Mar 2009
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    Typhoon Senior Member


    You can always fit an electric clutch to the alternator and size the pulleys so you get the correct alternator speed at the rpms desired, then de clutch when rpm becomes too high.

    Regards, Andrew.
     

  15. CDK
    Joined: Aug 2007
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    CDK retired engineer

    That is hardly a solution Andrew. There is only one correct rpm for an AC generator, so the clutch should disengage for any speed above and beyond that. If I have an AC socket, I want to be able to use it whenever I need electricity and it should supply what I expect. Not 90 v @ 45 cycles or 145 v @ 75 cycles because that would be lethal for some of the equipment.
     
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