Those whoo spend lots of time aboard, generator question?

Discussion in 'Boat Design' started by parkland, Aug 21, 2013.

  1. parkland
    Joined: Jul 2012
    Posts: 700
    Likes: 6, Points: 18, Legacy Rep: 40
    Location: canada

    parkland Senior Member

    I was just thinking about this today.
    We know there are gas and diesel powered generators,
    we know there are batteries, solar panels, even wind generators.

    Is there such a thing, as a small 2 - 5 hp diesel engine generator, that runs a 12 v alternator to charge batteries, that will start automatically?

    I'm just thinking, if I do actually ever buy or build or aquire a boat in some fashion,
    I think I'd have a few solar panels, batteries, and a generator that would automatically start if
    the batteries got low, and shut down when they were full.

    Does something like this exist; or has anyone built one from scratch?
     
  2. gonzo
    Joined: Aug 2002
    Posts: 14,449
    Likes: 640, Points: 123, Legacy Rep: 2031
    Location: Milwaukee, WI

    gonzo Senior Member

    It is a fairly straightforward system. A switch is actuated by voltage. You can set the voltage at which the generator starts and stops. It would make more sense to use electronics, but you can use an old style voltage regulator too.
     
  3. michael pierzga
    Joined: Dec 2008
    Posts: 4,862
    Likes: 115, Points: 0, Legacy Rep: 1180
    Location: spain

    michael pierzga Senior Member

    Ive never heard of it.

    You can wire a generator for auto start on supply demand then run off a timer switch to stop. .

    Why would you want such a complex silly system on a simple boat ?
     
  4. CDK
    Joined: Aug 2007
    Posts: 3,324
    Likes: 147, Points: 63, Legacy Rep: 1819
    Location: Adriatic sea

    CDK retired engineer

    For such low power levels nobody uses a diesel. Auto start diesel generators above 10 KW are available, packed in a soundproof "coffin", water cooled. Intended use is power generation in luxury yachts, so the prices are staggering.

    I once built an auto start generator with 350 Amps 14V output. Sounds easy but becomes quite complicated because of the many requirements for a fail safe performance. Oil level, coolant, temperatures must be checked before starting and during operation and you don't want the diesel to start whenever the inrush current of a fridge causes a voltage drop.

    For my own backup system I use a small 4 stroke petrol engine and a 1:4 belt driven 90 Amp alternator. The brand new Chinese engine costs $150, for the whole project I spent less than $300 including flexible engine mounts and a stainless exhaust.
     
    1 person likes this.
  5. tunnels

    tunnels Previous Member

    There's clever people that could make what you are looking for ! :D:p
     
  6. FAST FRED
    Joined: Oct 2002
    Posts: 4,519
    Likes: 109, Points: 63, Legacy Rep: 1009
    Location: Conn in summers , Ortona FL in winter , with big d

    FAST FRED Senior Member

    A small 3-5 hp engine will not be large enough to charge much more than 2 6v batts , wired for 12v , in a modest run time.

    IF your house set is much more than 100lbs of lead , a truck 135A (about $135-$150 ) and external 3 stage regulator will shorten the noisemaker on time a great deal.

    Here is an auto-start,

    http://www.backwoodssolar.com/magnum-auto-generator-start-module

    They also have a car alt and small engine kit.
     
  7. Tad
    Joined: Mar 2002
    Posts: 2,303
    Likes: 185, Points: 73, Legacy Rep: 2281
    Location: Flattop Islands

    Tad Boat Designer

  8. FAST FRED
    Joined: Oct 2002
    Posts: 4,519
    Likes: 109, Points: 63, Legacy Rep: 1009
    Location: Conn in summers , Ortona FL in winter , with big d

    FAST FRED Senior Member

    That is interesting and expensive , yet from their literature I am not sure if the best part of using an engine /alt /inverter is done.

    That is the ability to operate at a variable speed which will load the engine far better at light loads.

    Variable speeds will allow the engine to burn less fuel per KW produced , and make loads less noise while operating at reduced RPM.

    Welding equipment has been using variable speed for 60 years.
     
  9. parkland
    Joined: Jul 2012
    Posts: 700
    Likes: 6, Points: 18, Legacy Rep: 40
    Location: canada

    parkland Senior Member


    It would have to be smarter than that, otherwise the engine would start with each power surge, and immediately shut off.
    Although, I suppose if you had a relay, and big capacitor, you could engineer a minimum run time.
     
  10. parkland
    Joined: Jul 2012
    Posts: 700
    Likes: 6, Points: 18, Legacy Rep: 40
    Location: canada

    parkland Senior Member

    I suspect so, and I even had a few ideas.
    Didn't want to think about designing something from scratch, if a cheap option already existed.
     
  11. parkland
    Joined: Jul 2012
    Posts: 700
    Likes: 6, Points: 18, Legacy Rep: 40
    Location: canada

    parkland Senior Member


    I'm not an electronics expert; but what about the reference voltage is fed to a capacitor through a diode, so that the starting relay won't engage until xxx minute below xxx voltage, and then when it starts, it uses the second capactior to determine a minimum run time, and also activates a relay with a resistor, so that the reference voltage needs to be 14.5 volts or so before it will shut off.

    :rolleyes:

    There are lots of 3 - 6 hp diesels for cheap, I thought this would make a lot of sense, but it is completely possible, that once again, I am totally wrong, lol. ;)
     
  12. gonzo
    Joined: Aug 2002
    Posts: 14,449
    Likes: 640, Points: 123, Legacy Rep: 2031
    Location: Milwaukee, WI

    gonzo Senior Member

    Switches can be set at a minimum and maximum voltage, with a delay for actuation. The delay prevents the generator from starting each time there is a power surge.
     
  13. parkland
    Joined: Jul 2012
    Posts: 700
    Likes: 6, Points: 18, Legacy Rep: 40
    Location: canada

    parkland Senior Member

    Well that sounds like a simple and elegant setup!

    How could one take care of the fact though, that as soon as it starts charging, the voltage will be higher than a full battery, even if it's low still?

    For EG, roughly,

    a 12 V battery, empty is what, 12.2 v or so? Full is 12.8 v or so?
    Charging, 13.4 is empty, and 14.4 is full roughly?

    So how could one account for that?
    Maybe make it so it runs for 10 minutes, disconects alternator from battery, checks voltage, then decides if it should run and charge more, or shut off ?
     
  14. philSweet
    Joined: May 2008
    Posts: 2,326
    Likes: 186, Points: 63, Legacy Rep: 1082
    Location: Beaufort, SC and H'ville, NC

    philSweet Senior Member

    As CDK pointed out, and I want to repeat, There are a lot of problems that are introduced when you do this. I worked with some remote power systems in the forest service. Ostensibly campground water systems with an over-sized storage tank. The tank was because it was a fire cache for tanker trucks. Onan generator fully auto to maintain a full tank. I manually disabled one of these things three times after the Onan service tech "fixed" it three times. Eventually, out of frustration, I spent a day on it and figured out what was wrong. There was tremendous complexity to the control system, and a sensor ended up on the wrong output of a relay. To give you one example of the sort of problem common to these. Engine runs low on oil. Oil sensor shuts down engine. Demand sensor restarts motor because the oil sensor is disconnected during the starting process for 30 seconds. So engine runs half a minute and shuts down. This continues until the battery dies or the starter pukes. If you ever get a call on one of these - take a starter and a pair of new batteries. I've never seen one not kill the battery, and the starters take a beating on virtually any fault. It's also harder than you might think to figure out how to provide a switches for maintenance that disables autostart without someone forgetting to reengage it or lets you manually test all the features after maintenance.

    So be prepared for some elaborate troubleshooting and realize that a dead battery or dead starter isn't the problem with the broken motor, it is only the symptom. Otherwise you'll be back the next day to put another starter and battery on it. The USFS/Onan systems ran off programmable Siemans industrial controllers. They were tied to the fuel tank, the water tank, and the genset with maybe 20 inputs and quite a few pages of ladder code.

    There are battery monitor systems that can send an auto start/stop signal to virtually any genset to control battery charging. But knowing how to feed the signal onto the generator without defeating the genset's own safety protection circuits takes some experience as far as the level of risk from different problems. Buy one with an auto start/stop terminal. This is often an option now.

    http://www.cumminsonan.com/autostart/
     

  15. michael pierzga
    Joined: Dec 2008
    Posts: 4,862
    Likes: 115, Points: 0, Legacy Rep: 1180
    Location: spain

    michael pierzga Senior Member

    This system would cause the generator to start everytime a high load dc circiut is energized and the dc voltage drops.

    The correct system would monitor the AMP hour capacity of the bank. 1000 amp hour bank..when the bank discharges to something like 750 amp hour the charge circuit is activated.

    What is the reason for having this complex auto system ?

    I live with a generator , off shore power, for 200 days per year and have never found the need.
     
Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.