Charging batteries without generator or shore power.

Discussion in 'OnBoard Electronics & Controls' started by B33RND, Aug 22, 2009.

  1. B33RND
    Joined: Jul 2009
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    Location: Netherlands

    B33RND Member

    Hello,

    I am building a 17 meter boat without generator for charging the battery bank of 1000 Ah. The main engine of 200 hp is the only power source and will run 4 to 5 hours daily in which the battery bank need to be charged for the forth coming night. My daily consumption will be 500 Ah when sailing and 250 Ah when not sailing.

    My question is if somebody see possibilities how to practically fulfill those requirements and what the objections are...

    Thanks in advance,

    Berend
     
  2. WotEver
    Joined: Aug 2009
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    Location: Nuneaton, UK

    WotEver Junior Member

    Hi Berend,

    Ideally you'd be looking for 200A (maximum) from your alternator(s), and this would get the bank into acceptance pretty quickly (2.5 hours for 500Ah usage). However, a total running time of 4 to 5 hours would not get them up to 100% charge. That's not unusual, most folk only cycle batteries between 50% and 80% SOC even if they don't realise it.

    Here's a (UK) link for some high current alternators: http://www.prestolite.com/pgs_products/n_alt_results.php?item_series_id=100&series_name=4800-4900

    Hope that helps,
    Regards,
    Tony
     
  3. B33RND
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    B33RND Member

    Hello Tony,

    Thanks for your reply. But in that case I'll probably need two pieces of alternators on one engine. Because the maximum amperes of alternators are only 140A/24V as I have seen.

    Are there objectives to your approach? Are there other options as well?

    Thanks,

    Berend
     
  4. WotEver
    Joined: Aug 2009
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    Location: Nuneaton, UK

    WotEver Junior Member

    Hi again,

    That link I gave in my first post showed several 200A 24V alternators.

    Other approaches:
    1. Ideally, work out how to reduce your consumption
    2. If you're still going to be drawing 500Ah then you'd be better off with a 1500Ah battery bank as you'd only drop them to around 70% SOC which would be easier to replenish in your short timescale. You could (should) then add a second 100A alternator.

    As a rule of thumb, your maximum charging current should not exceed around 20% of your battery capacity or you risk the chance of damaging the batteries (buckling the plates).

    Oh, and you'll need some SERIOUSLY large cables for efficient charging at those currents - 150mm sq or thereabouts. You could use smaller cables (many do) but you'd then HAVE to have a battery sensing alternator controller to counter the voltage drops.

    If you have a lot of time to spare and you REALLY want to understand a lot of what's involved in battery charging then check out the techical information at this site.

    Regards,
    Tony
     
  5. CDK
    Joined: Aug 2007
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    Location: Adriatic sea

    CDK retired engineer

    B33RND with 500 Ah daily power drain, a capacity of 1000 Ah is a bit small.
    Batteries have a much longer service life when cycled between 75 and 100%, unless you install deep cycle types for which you have to pay a lot more.

    And what are the objections against mounting a 2nd generator? You could even wire the 2nd to be used only when necessary.
     
  6. Guest62110524

    Guest62110524 Previous Member

    cdk, I had approx 875 batts on my last
    we used only a 75 amp/ht 24vdc alt , was plenty
    sailing yacht
    of course you would double this for 12 volts
    one thing , you probably arer aware of anyway, make sure you load the crank , side loading evenly
    then you could have assist wind gen and towed gen, and solar panals etc etc
     
  7. CDK
    Joined: Aug 2007
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    Location: Adriatic sea

    CDK retired engineer

    Nothing wrong with that.
    But this "B33RND" has something very special in mind because he expects to draw 500 Ah at 24V every night. A lightship perhaps?
     
  8. WotEver
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    WotEver Junior Member

    Desalination plant? :)
     
  9. B33RND
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    B33RND Member

    Thanks for the posts guys.

    Well, I am just building a average 17 mtr power boat, not a light ship:p . I am planning to use Traction batteries but, CDK, you are right that either the 1000 Ah battery bank is to less, or my calculation of power consumers is wrong :confused: . I think the last is the case. My actual load according my calculation is currently 425 Ah which is also according WHOOSH very much.

    May I ask in that regard your idea of power drain from: Radar, AIS (send and receive), GPS and Depth Sounder? All of them are 24 V.

    Another question: Is there a difference in power drain of lights of 24V and lights of 220V? And how much power do designers usually count for a average 24V ceiling light?

    CDK, the reason I at least want to try without generator is the simplicity of the whole engine room: no generator (often bad quality), no additional dry exhaust (I don't like wet), much less hull penetrations (potential dangers), only one keel cooler, a single power source (so easier electrical installation), fuel polishing, and more of that kind of cons compared to just one single engine.

    I am building a seaworthiness boat, and I consider boats with wet exhaust not as very seaworthiness because of the exhaust to close to sea level and the amount of hull penetrations and the potential danger of drowning the engine. Everything is fine as long as the boat will not go deeper than her designed waterline. As soon as that will be the case by some reason at sea, your boat with engine becomes useless and it's the best to disembark :) .

    Thanks in advance ,

    Berend
     
  10. WotEver
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    WotEver Junior Member

    Hi again, Berend.

    220V lamps will mean an inverter which will have an efficiency (at best) of 95% - so for that reason they'll actually draw more power than 24V lamps for the same light output.

    If you can source 24V LEDs they will reduce your power consumption considerably as opposed to incandescent lamps.

    As a rule of thumb, CDK was spot on when he said that you should aim for a battery bank 3 times your expected daily usage. It's the same point that I made in Post #4. So once you know your daily usage, you know the size of battery bank. Once you know that, divide by 5 to get the ideal size of alternator(s).

    As for all the sea-going questions I won't pretent to know anything about that subject and will allow others to comment :)

    Regards,
    Tony

    Edit to say that when I wrote "If you can source 24V LEDs" I meant "If you can source 24V LEDs for your fitments". There are plenty of 24V LED lamps around.
     
    Last edited: Aug 24, 2009
  11. yipster
    Joined: Oct 2002
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    yipster designer

    deep charge bat's nowaday's cost 10/20% more and wouldnt really call that a lot
     
  12. WotEver
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    WotEver Junior Member

    But do you truly get 20% more life out of them? Plenty of folk say no, but I have done no tests myself so can't state either way.

    Has anyone got any proof (other than manufacturers' claims) that a deep cycle battery will last longer than a traction battery if never discharged below say 65%?
     
  13. B33RND
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    B33RND Member

    Yipster, thanks for your comment. Can you motivate it?

    Thanks in advance,

    Berend
     
  14. yipster
    Joined: Oct 2002
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    yipster designer

    after reading up on the net on deepcycle batts i bought these delphi's after a to heavy, big and expensive mastervolt gel batt turned bad after neglect
     

  15. tkk
    Joined: Jul 2009
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    tkk Junior Member

    Are you running all that stuff also when you are not running the boat? If not, it should be taken into account in your calculations.
     
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