Electric Motor Questions

Discussion in 'Functional Gear & Equipment' started by birddseedd, May 31, 2016.


  1. birddseedd

    birddseedd Monkey

    anyone know about electric motors?

    i'm wanting to power a houseboat with one. I was thinking a fork lift motor. i'm looking to be the equivalent of a 60 horse around 4200 rpm. and run it off of solar.

    watchya think?
     
    UncleMorgan likes this.
  2. Tevin

    Tevin Monkey+

    Hmm well I don't think you'll get too far with that idea

    Firstly, I don't think there are any 60 horsepower forklift motors. A motor of that size would weigh well over a ton. And you'll need a lot of batteries too.

    Second, 60 horsepower equals roughly 44,100 watts. With even the largest panels putting out around 250 watts in strong sun, that means you would need about 175 solar panels, each being about 5'x'5. Do the math. You better have a really big boat.
     
    Tully Mars and UncleMorgan like this.
  3. BTPost

    BTPost Old Fart Snow Monkey Moderator

    You are in a fantasy world if you think you can power a 60 Hp Motor from a Solar/Battery Setup... Do the Math, and see for yourself...
     
    Tevin and UncleMorgan like this.
  4. MountainMariner

    MountainMariner Clearly Ambiguous

    175 solar panels would make a great sail though...
     
  5. BTPost

    BTPost Old Fart Snow Monkey Moderator

    Would make the vessel a bit Top Heavy, and unstable, don't you think....
     
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  6. MountainMariner

    MountainMariner Clearly Ambiguous

    Easy. Add lead ballast in the keel to offset the solar sail. Let me plug some numbers in my stability calculator...
     
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  7. kellory

    kellory An unemployed Jester, is nobody's fool. Banned

    Use the battery back as ballast at the keel (inside of course) and keep the motor low and use a set of drive gears and chain to drive the prop. It should be much more stable that way, no matter what type of motor you use, just less efficient in power transfer.
    Let the engineers have some real numbers to go by, and they can be of more help.
     
    UncleMorgan likes this.
  8. birddseedd

    birddseedd Monkey

    They do look to be pretty heavy, just under half a ton. tho that's only about 3x what a full load of gasoline would be.
     
    UncleMorgan likes this.
  9. kellory

    kellory An unemployed Jester, is nobody's fool. Banned

    You have to go huge, high dollar, and high efficiency to go solar.
    This is the Solar Sailor. [​IMG]
     
    UncleMorgan likes this.
  10. birddseedd

    birddseedd Monkey

    I think iv got enough room for the panels that are on the front of it. maybe not the top without doing something similar.

     
    UncleMorgan likes this.
  11. kellory

    kellory An unemployed Jester, is nobody's fool. Banned

    Good luck, but I would suggest you allow the solar experts, and engineers, both time and real numbers to work with, before spending a dime.
     
    UncleMorgan likes this.
  12. birddseedd

    birddseedd Monkey

    im sure it can make a boat go. but its seemingly not going to work without a lot of panels. the same with cars, they go, but have to have something more powerful to charge the batteries with.
     
    UncleMorgan likes this.
  13. Airtime

    Airtime Monkey+++ Site Supporter

    So, 60 HP is 44,760 watts of power. The motor is roughly 85% efficient converting electrical energy to mechanical energy which means you need to supply about 52,000 watts to the motor to get 60 HP to the prop drive system.

    There are batteries such as lithium-polymer but those would be quite expensive. A more affordable battery would be lead acid deep discharge.

    A group size 27 deep discharge battery has a capacity of about 90-100 amp hours but you shouldn't discharge below 50% and ideally not below 75% if you want decent life. If you pull 50 amps from it you can get about 550-600 watts for about an hour before hitting the 50% discharge limit. So you would need about a hundred batteries for an hour of cruise time. A 27 battery is generally about 50-54 pounds. So you are looking at about 2 and a half tons of batteries to be able to run 60 HP for one hour for fewer than 1000 discharge cycles and only half hour run time if you want several thousand recharge cycles.

    Now the size/number of solar panels to recharge all that is similarly large. One decent panel is 250 watts. With say 10 hours of good sun, 90% efficiency for the charge controller and 90% efficiency in the battery for energy storage and subsequent energy dissipation, you'd need at least 26 panels totalling over 200 square feet to recharge all your batteries.

    So, that all sound reasonable for a boat?
    Have fun.
    AT
     
  14. techsar

    techsar Monkey+++

    A common conversion is 3/5...a 3 hp electric is comparable to a 5 hp gasoline engine, so if you take 60x3/5=36...36 hp electric. Several on fleabay in the 40 horse range ~ various voltages, but most are in the 1750-1950 rpm range...and either 240v or 440v/3ph. Not sure that's a good idea on the water ;)
     
    UncleMorgan likes this.
  15. birddseedd

    birddseedd Monkey

    How are cars able to do it with much less than that?
     
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  16. techsar

    techsar Monkey+++

    Many hybrid vehicles run 400-600 volt motors, 52,000(watts)/500(volts) and your looking at around 100 amps+/- . As the vehicle nears cruise speed, power requirements tend to drop, might only need 25 hp for cruise (40 amps?)..plus the engine helps during periods of high load.
     
    UncleMorgan likes this.
  17. ghrit

    ghrit Ambulatory anachronism Administrator Founding Member

    You may wish to check the water you intend sailing in. If you put the batteries down as keels, you are going to draw a lot of water.
     
    UncleMorgan likes this.
  18. birddseedd

    birddseedd Monkey

    folks make them out of fork lift motors. they have even used 2 of them to run bigger (compared to cars) trucks. Havn't done it myself, so hard to really say what it takes and what they get out of it.
     
    UncleMorgan likes this.
  19. techsar

    techsar Monkey+++

    Add salt water to lead-acid batteries, and you can get some really nasty (as in deadly) gas forming, too.
     
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  20. Airtime

    Airtime Monkey+++ Site Supporter

    They need much less than 60 HP at cruise. They have regenerative braking systems. They generally use Li-Po batteries that are much lighter and have higher power density but cost a lot more. Interesting it is because of the limitations of purely electric vehicles that leads to hybrid designs.
     
    UncleMorgan likes this.
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