current wisdom on electric

Discussion in 'Hybrid' started by Anatol, Dec 22, 2015.

  1. Anatol
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    Anatol Senior Member

    2016 in a couple of days. Electric cars etc advancing rapidly. Several (numerous) commercial sailboat edrive packages available. What is the current wisdom on DIY solutions for a heavy displacement cruising boat?

    Halcyon is heavy but slim, slips through the water nicely. I'm intending to replace my aging atomic 4 before it rusts through. It was rated at 30 hp 50 years ago, I doubt I get 20 now :) I'd use the existing prop shaft but change prop...?

    Brushless motor is recommended for safety reasons and permits regen (very nice). 48-72 volts. Lead acid batteries. What about reduction and prop style?

    Thinking about a diesel or gas gen set for backup.

    Where are appropriate take-out motors turning up? Are, ie Leaf motors appropriate, or build up from basic components? The diy electric car folk talk about golf buggy motors and forklift motors...

    Big amps flying around the bilge is a scary as gasoline...and omg - the electrolysis potential!

    interested in any (useful) comments.
     
  2. gonzo
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    gonzo Senior Member

    First, why are you replacing the Atomic 4 for an electric setup? 72 V will kill you, so the insulation and installation needs to be done properly. Lead/acid batteries are not to efficient. Lithium Ion are better, but have some problems too that need to be addressed. Cobbling a siystem together with old golf cart parts, etc. is not a good solution. The whole system needs to be matched. Also, the power of the electric motor has to be the same as whatever the gas engine was producing. A replacement diesel engine will be cheaper.
     
  3. Anatol
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    Anatol Senior Member

    because, much as I love it in principle, its had salt water running thought it for 50 years and will rust through any day, its smelly, inefficient, ecologically unsound and requires more labor than its worth. Annual carb rebuilds are getting old.

     
  4. PAR
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    PAR Yacht Designer/Builder

    Well the math is pretty simple, so work up a wattage schedule for a 22 KW motor. After you wake up from fainting over the price (compared to an Atomic 4 repower), we can talk.
     
  5. FAST FRED
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    FAST FRED Senior Member

    Electric cars do not have the same power requirements as a boat.

    If you want to spend thousands making a very inefficient statement , have fun , but don't ever expect to sell the boat.

    Coal or nuke powered boats (your power source) have limited range .

    If you just want to do the best you can , a new smaller gasoline or diesel run on bio fuel (no winter operation) would be better choice.

    Perhaps someday when a battery weighs the same as 10gal of fuel , and holds the same energy content, it will be an option.

    We have been waiting for 120 years for this battery , keep the faith!
     
  6. gonzo
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    gonzo Senior Member

    The most important difference between lead/acid and Lithium Ion batteries is the duty cycle. Lead/acid should be charged at 1/10C for durability, while Lithium Ion can be charged at 10C. That is 100 times the charge rate (1/100 of the time). Lithium Ion can accept shorts burst of charge, like when there is a wind gust and the wind generator produces more power. Also, lead/acid batteries can only be discharged to about 65% of their capacity before the voltage is too low to be effective. That also shortens their life. Lithium Ion, depending on the chemistry, can be cycled to 15% or less.
    What makes you think the Atomic 4 will rust through any day? If it is not leaking water into the oil, a heat exchanger will be a cheap and effective way to make it last for decades to come. A rebuild kit is not too expensive either; maybe $400.
     
  7. cmckesson
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    cmckesson Naval Architect

    Works for me

    Our boat was originally offered with an Atomic 4, and for the past ten years or so has had 72V DC electric drive, with lead-acid batteries. Works for me, I am quite satisfied. Are there downsides? Yes, sure. They're just different from the downsides of a combustion engine.

    Chris McKesson

    (Err, because it might matter in this case, that's:

    Dr. Chris McKesson, PE, P.Eng
    Naval Architect)
     
  8. gonzo
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    gonzo Senior Member

    Have you done an economic analysis? Compare $400 to the thousands invested in an electric system. I don't see any fuel savings considering all the losses on charging and discharging either. If you use solar and wind charging, there may be some savings, but the initial cost increases too.
     
  9. daiquiri
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    daiquiri Engineering and Design

    Folks, if the guy wants to use electric, let him use electric. He seem to be aware of the financial drawbacks, or it is perhaps just my impression. :)

    Anatol: for what it's worth, the following articles by Nigel Calder could be a good start (in case you haven't read it yet):
    http://www.passagemaker.com/articles/technical/power/hybrid-science-part-1/
    http://www.passagemaker.com/articles/technical/power/the-science-of-hybrid-propulsion-part-2/
    http://www.passagemaker.com/article...cience-of-hybrid-propulsion-the-great-debate/
    http://www.oceannavigator.com/January-February-2011/Battery-revolution/

    Some other points of view (read them wisely between the lines too):
    http://www.powerandmotoryacht.com/boats/engines/hybrid-engines-for-boats
    http://www.yachtingmagazine.com/sea-greener
    http://www.proboat.com/solar-powered-one-design.html,
    http://www.proboat.com/nimbus.html

    And then, there is this excellent thread in this forum: http://www.boatdesign.net/forums/boat-design/batteries-new-battery-technologies-21869.html

    Hope these articles will give you a sufficient info for the start.

    Cheers
     
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  10. Anatol
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    Anatol Senior Member

    Boatowners know, or find out, that dreams of resale value are false. Anyway, I doubt an electric system would reduce the value over a rusted out A4 :)

    Yes, gasoline packs a a huge punch. But you can't speak of gasoline or diesel without acknowledging the vast and polluting infrastructure of wells, supertankers and refineries. Compared to that, coal fired power plants are a lesser evil, maybe. in any case, as noted, regen is the big draw. A diesel auxiliary can't make any of its own power.

    And of course, there was a time when sailboats didn't have auxiliaries. Most of human history, in fact.

    Batteries are a storage technology, not an energy source. Energy storage, like will never be 100% efficient, asking for 50% is optimistic. But the case for any energy conversion, including explosions in reciprocating cylinders.

    My question was not: is an electric system 'better' or 'cheaper'? I simply asked what the best options are in 2016, understanding that technologies change and this one is moving fast.

    Diesel electric systems are the energy efficient choice for giant trains. An efficient diesel genset backup, where the engine runs at optimum revs, feeding into the battery bank, seems like an optimal compromise.
     
  11. PAR
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    PAR Yacht Designer/Builder

    There are several considerations with the electric options currently available. Diesel/gas to electric arrangements are less efficient than more conventional arrangements, with conversion losses, costs and complexity. These systems only become viable with very large electrical load requirements, such as hundreds of cubic feet of refrigeration or other high load needs. In these cases propulsion requirements are typically a small fraction of the total electrical requirement, which is what makes them the better choice.

    In pleasure craft, systems are coming around, decreasing costs somewhat, but still are difficult to justify weight, complexity and loses, with propulsion being the the primary need, especially in smaller sizes, such as your Atomic 4 replacement.

    I did just as you wish a couple of decades ago, replacing my Atomic 4 with a 24 VDC washing machine motor and a belt to my shaft. I just needed to motor up a river, out to the local racecourse and back at the end of the day. Total traveling time was just over 2 hours and I was near the end of battery capacity as I pulled back into the slip. An overnight charge was all I needed to be ready again, but 2 hours range is an awful penalty to pay, just to have an electric setup of similar weight. Since then, I could likely improve the range a bit, for the same weight, but not by enough to consider it a true A-4 substitute, though for my needs at the time, good enough.

    This is where you're at, having to access your wattage requirements and plan a system to accommodate this need. If cost isn't a consideration, you have lots of choices and reasonable range, though still nothing compared to diesel/gas replacements, in terms of weight and complexity. When you compare everything, electric still has some way to come, so it all depends on your needs and intended uses. If intermittent electric propulsion is all you need, it might be fairly viable, but if you have a high propulsion requirement, the gap between diesel/gas to electric
    widen quickly.

    As to specifics, for your needs, well you have to make the assessment, so the element routes you can take can be researched.
     
  12. FAST FRED
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    FAST FRED Senior Member

    " An efficient diesel genset backup, where the engine runs at optimum revs, feeding into the battery bank, seems like an optimal compromise."

    True but the engine loads must be maximized between the heaviest charging the batts can accept and having some left to push the vessel.

    Its just as efficient to simply use the small engine in a gen set to just push the boat.

    The hassle is energy conversion , creating DC , charging the batt , then using DC has costs in the 25% to 50% area.

    So powering for an hour while charging , running on DC for 15 to 30 min and charging again for an hour will burn far more fuel than simply operating a small diesel with transmission loss in the 3% loss range.
     
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  13. gonzo
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    gonzo Senior Member

    Anatol: diesel electrics are expensive setup that are justifiable when you need precise speed control, like for example in a survey ship, a train, or a tug. In commercial use, the life of batteries can be amortized because of the amount of use. Lead/acid batteries, because of their slow rate of charge, can't make use of burst of surplus energy. That is why they are not used on hybrid systems. If you are looking at $/amp ratio, it is going to be poor compared to rebuilding your existing engine or even replacing with a new one. It seems like you decided to have a hybrid system because it is cool and fashionable and now want to find a justification for it. If you want to tinker and have the money and time, it can be an entertaining hobby.
     
  14. philSweet
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    philSweet Senior Member

    I think diesels are getting better faster than e-power is getting better. The gap is widening. Most of the decisions with e-power revolve around the recharging of the batteries. Get a handle on your recharging requirements, and then look at the costs of chargers and BMSs that can do what you want. You can easily spend more on just the charging hardware and BMS than on an rebuilt A4.
     
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  15. gonzo
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    gonzo Senior Member

    An electric motor alone without controls or wiring costs several times the cost of rebuilding a gas engine
     
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