electric motor outboard conversion

Discussion in 'Propulsion' started by Archangl7, Aug 5, 2017.

  1. Archangl7
    Joined: Aug 2017
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    Location: clearwater, fl

    Archangl7 Junior Member

    I plan on making a 14ft skiff i have solar/electric powered using a existing lower unit from a older jonson 9hp with a locked up powerhead. I do plan on making many of these in the future, but i have to get a design down. I have a 300w solar panel, and will be using 6 (of the 24 i have) 12v 100AH batteries. I was planning on using a golf cart motor, but i just discovered that the drive shaft end is open and not supported by a bearing. The idea was that they are readily available, but i dont know if i want to go through the headache of making the mods for that to work. So, i turn to you all for suggestions!
     
    Last edited: Aug 5, 2017
  2. Mr Efficiency
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    Mr Efficiency Senior Member

    What is the HP rating of the golf cart motor ? And when you say "open", you mean what ?
     
  3. Rumars
    Joined: Mar 2013
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    Rumars Senior Member

    He means the motor does not have a faceplate and bearing at each end. One end is open and ends with a female splined shaft without a bearing. It is designed to bolt directly to a transmission as a integrated unit.

    I would be more concerned about weight. 24 12V batteries in 14ft skiff? I hope you did't had any hopes of planing. I suppose he solar panel is just for show, keeping the batteries topped up not for driving around? For the motor look at some PM motors, like the Mars.
     
  4. Archangl7
    Joined: Aug 2017
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    Location: clearwater, fl

    Archangl7 Junior Member

    Thanks for the replies so far, and i just realized i misspelled conversion, lol. I did edit what i could to state that i am only going to be using 6 of those 24 for a single boat. Maybe 3 if i can get the performance i wish for. The solor panel is for charging only, but will be permanently fixed on the boat. Are all the mars motors so expensive? I can get a complete setup from a golf cart for $150, and that 2HP.
     
  5. alan craig
    Joined: Jul 2012
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    alan craig Senior Member

    6 x 12v 100Ah batteries will weigh about 360lbs as leisure batteries, much more as deep cycle batteries. Coincidentally I have just launched my own 14ft electric/rowing skiff; picture attached. I used 2 x 12v 100Ah leisure batteries and they weigh 27kg (about 60lbs) each. I used a 3hp Evinrude leg and attached a large brushless motor to it from the model airplane hobby. There is a thread about it on here. It takes about 25 to 30 Amps (500 to 750 watts) maximum to go faster than you can continuously row. Even more coincidentally, I plan to add 300Wp of solar power so I will be very interested to see how you get on.
    The hardest part of making the electric conversion was waterproofing the controller and the motor.
    edit: image added. p.s. pic shows boat with 54Kg of batteries on board.
    P1000465 - Version 2.JPG
     
    Last edited: Aug 6, 2017
  6. Archangl7
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    Location: clearwater, fl

    Archangl7 Junior Member

    The batteries i have are not fullsize, they are about 40lbs each, not much of a difference, but some... Could you link that thread? Is it this one Brushless Outboard https://www.boatdesign.net/threads/brushless-outboard.57088/? When i started reading that one i kind of jumped for joy finally seeing some discussion and answers. The main reason i wanted to do this was the crazy prices i have seen on other electric outboards. I build arcade machines from scratch for a living, and i do so to keep costs far below anyone elses. I have a degree in electronics and want to do this real bad.
     
  7. Mr Efficiency
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    Mr Efficiency Senior Member

    It would be beyond my ken to accurately match up electric motors to old outboard legs, with prop sizes and gear ratios adapted to internal combustion engines. You also have a small issue with the area where the exhaust exited, this could create a little bit of drag, though a tapered cone would help that.
     
  8. Rumars
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    Rumars Senior Member

    I don't know what your goals are but if you can get the complete setup (motor, controller, throttle, contactors, fuses, etc.) from a golf cart for 150$ then it is worth making an endplate for the motor. It's not rocket science but you usually do need access to a lathe. As for the crazy prices, yes those are retail prices for new motors. You are comparing new to used.
    I don't want to discourage you but making a business out of such conversions is not gonna make you money. You can do it as a sideline for a hobby, but I would not plan on living of it.

    The electric motor rpm needs to match the original outboard motor rpm range in order for the prop to work. So look up the outboards and electric motors specs.

    Have you never wondered why nobody puts a big solar panel on a small electric boat? Let's see: your setup of 6 12V 100Ah batteries is 7200Wh. With a 50% DOD that means you have 3600Wh to use. Replenishing that with a 300Wp panel would take 12h under laboratory conditions. In real life it might take 3 days. And is enough for 2.5h of driving the motor at rated power. Solar only works if you have a boat with lots of space and small power requirements.

    Here is a video about adapting such a golf motor.
     
  9. Mr Efficiency
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    Mr Efficiency Senior Member

    Why would people change golf cart motors, if they are good to go ? Or are these "wreckers" ?
     
  10. Archangl7
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    Location: clearwater, fl

    Archangl7 Junior Member

    There are golf cart salvage places near me. I live in clearwater FL, and there are tons to choose from. As for the comment about the hours its will last, that would be fine, 2.5 hours would do great for what i want it for. What are you refering to with "DOD" and the great loss in capacity? I had watched that video before i posted here. I typically do a lot of searching around before i post anywhere.
     
  11. Mr Efficiency
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    Mr Efficiency Senior Member

    Florida the golf cart capital of the world ? Oh well, you may be able to perfect something that works.
     
  12. Rumars
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    Rumars Senior Member

    DOD means depth of discharge, or how much are you able to regularly discharge a battery before it dies from abuse. Deep cycle applications like the ones for a golf cart have 80%DOD and it tapers down to about 20%DOD for starting applications. So depending on what type of battery you have you are hauling around more or less dead weight.
    Batteries have a nominal capacity rated at C20 that is the current given over 20 hours. So 100Ah capacity battery is able to deliver a 5A current for 20 hours. If the batteries have to deliver more than that the usable capacity diminishes and if less it increases. The manufacturer gives a table with the available values for different C ratings.
    So for your planned 6x12V batteries and 2hp motor asuming series connection and nominal motor power you have 1500W / 72V = 20.83A. For 100Ah batteries that is a C5 rating. So you look up what capacity actually exists at C5 and what DOD is recomended and calculate how much energy is actually available to you before taking into consideration any conversion losses (controller + motor).

    As for the golf cart motor I repeat myself: if the price is for the whole cart then making a endplate and bearing is worth it even if you have to pay market price for the machining. If it's only for the motor it depends on how much you pay for the endplate.
    If you want similar motors with an endplate you can look at accessory drives from electric forklifts or pump motors.
     
  13. alan craig
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    alan craig Senior Member

    Archangl7, yes, that is my thread you linked to a few posts above! I am just about to add a bit more info to it.
    Yes, you are limited strongly by total energy (not power - it is easy to make a powerful electric vehicle or vessel using brushless motors) if you use lead batteries, but there are examples around such as planing wakeboarding boats, where the weight creates a bigger wake. But they still need many hours to recharge.
    The less power you use to travel the easier it becomes; and because of the scaling law, a smaller vessel becomes more realistic to be fully charged by solar power.
     
  14. Archangl7
    Joined: Aug 2017
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    Location: clearwater, fl

    Archangl7 Junior Member

    I was wrong the battery is a FIAMM FLX200 and the datasheet is here http://keyitec.com/FLX200 Data Sheet.pdf
    I got these for an amazing deal and paid around $17 each and got a rack to go with them for free.
     

  15. alan craig
    Joined: Jul 2012
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    Location: s.e. england

    alan craig Senior Member

    Amazing price, surely they must be secondhand? If you look carefully at the data on the pdf it shows what Rumar said, basically you get much more energy out if you discharge at a low rate and less if you discharge at a high rate.
     
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