Electric outboard drive for small cruisers

  • 13 Mar 2020 20:23
    Reply # 8825935 on 8809939

    I'm not a fan of splices if they can be avoided, why not get an extra Anderson connector and avoid the splices (with their additional resistance and potential failure points).  I'm admittedly a wiring weenie, years of designing and flying electric RC planes before it was popular or easy has left me loath to leave any extra electrons lying around.   Check you Anderson connector size, I linked to a 175A connector.  However the only link I found for Haswing and Anderson was for 50A connectors, but that must be for a smaller motor?

  • 13 Mar 2020 19:34
    Reply # 8825870 on 8809939

    As it has turned out when I tried to install the cables today, the cables supplied with the Haswing are just a little bit too short to get as far as the circuit breaker. It seems easiest to use a pair of splices, and since I have to buy more cable, it might as well be 35mm2. If I buy 1 metre each of red and black, and put the splices near the Anderson connector, I can easily get lengths of 1.1 metres instead of the existing 0.8 metre.

  • 12 Mar 2020 23:11
    Reply # 8824275 on 8809939

    My thoughts on solar were formed largely on our 12V system, your 24V system changes things a bit.  However, it is possible to get boost charge controllers so that it isn't necessary to have the panel voltage above the battery voltage.  My thought was that with the location of your panel, shading from the battens/sail is likely to be a problem and could knock out the output from the entire panel.  Two skinny panels parallel to the centre-line, each with a controller, would make it less likely for most of the solar to be lost with shading.  As usual, a set of compromises.

    The oceanvolt looks marvellous, although the price must be shocking.  I was going to go considerably lower tech.  My take on hydro or wind is that they both don't produce much power at low velocity, so you might as well just optimise them for higher velocity.  Low tech hydro would be a towed version similar to a Hamilton Ferris or Ampair.  For coastal cruising it would seem like something like a WattandSea might be more useful in that it would be easier to kick up and put down.  Perhaps an old trolling motor could be made to do the job.  The Haswing wouldn't have the ideal prop, but maybe it would be possible to get power out of it if you were to turn it backwards (to make the prop more efficient).  It probably has three wires running from the brushless motor to the controller.  If you had a way to disconnect those wires from the controller, and connect them to a rectifier, then you just need a charge controller to the batteries (maybe a cheap solar pwm controller).  Make a neat control box and you could have three modes for the motor 1)Power, 2)out of the water for low drag sailing 3)turned backwards and switched for generating when you're sailing in brisk winds.  It ought to be possible to experiment with a cheap second-hand trolling motor before experimenting with the Haswing.  Of course all of that isn't at a necessary for the first season, or maybe ever.

    I'm not sure about the wire calculator you used.  I usually use the Blue Sea systems Chart for sizing wires and they give a different result.  For 100A and a 7.4m round trip (7.6M on the table) run they would recommend 1 gauge for a 3% drop.  It would be easy enough to measure voltage drop during use and then only change things if it annoyed you.  3% would only be three extra amps lost at full throttle and things would be much better at the lower power settings you plan on using most of the time.  It's easy to be a voltage weenie, on the other hand you paid extra for a brushless motor, which is only about 10% more efficient than a brushed one.  Remember you're also likely to have few percent loss due to connections, resistance of the connectors, resistance of the thermal breaker etc.  By the time you get over 5% loss, it might be enough loss of range and max power to consider a wiring upgrade?

  • 12 Mar 2020 22:45
    Reply # 8824239 on 8809939


    I think my main question is answered in the MPPT controller's manual, pp 3/4.

    Magnetic compass? I have one, but I scarcely ever look at it. Soooo 20th century, my dear! GPS gives me a lot more nav info.

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    Last modified: 12 Mar 2020 22:48 | Anonymous member
  • 12 Mar 2020 21:16
    Reply # 8824123 on 8809939

    David, I'm pretty sure the PV panel gives a certain number of amps, the watts is determined by the battery voltage. I'd be confident that a horizontally mounted panel in British waters isn't going to exceed the controller's rating. Some panels have built in by-pass diodes so they can keep working if some cells are in partial shading, you might be lucky. 

    The wire sizings look fine to me, I'm intrigued to see if 30 to 100 amps through a 25sq mm cable circuit does funny things to your compass! 

    Also, when I've worked out how to clone myself to have time for all the projects I'd like to have a go at making a hydro generator, I've built a wind turbine from scratch so have a few ideas to throw at a DIY outboard genny. 

  • 12 Mar 2020 20:08
    Reply # 8823963 on 8809939

    You raise some interesting points, Darren.

    I chose one large panel because that way I get 72 cells and a quoted max power voltage of  38.9V . I can afford to lose some output, and still stay over the 28V I will need to charge the battery. If I'd gone for two smaller panels in parallel, to get the same wattage, I would have less max voltage to eat into. If I'd gone for two smaller panels in series, the voltage would stay up, as I could get up to 72 cells again, so maybe that would be an alternative. Within the space I have available, I could get the maximum wattage with the single panel.

    Then there's the question of how the controller processes up to 38V and up to the panel's max 10A, to put the maximum power at 28V into a 24V battery. What proportion of the nominal 360 watts will the MPPT controller pass on to the battery? 360 watts at 28V means the current would be 12.8A.

    My intention is to see whether the output of the panel limits me in any way, other than having to have enough patience to chill out at anchor waiting for some power to be generated. That would be good for me, to develop a bit more zen. If I genuinely need more power for safety, my preference would be for a wind generator. Having got rid of the drag of a prop in the water, I'm loath to put one back in for hydro-generation. It seems to me that to get good efficiency they need a variable pitch prop, like the Oceanvolt. That way, when there is full boat speed and an excess of wind power in the sails, the hydro power can be turned up to max, but when trying to make headway against a light breeze, the blades can be set to feather.

    With the batteries under the aft end of the cockpit, the weight distribution is very similar to how it was with the Tohatsu, and with that, there was a tendency to go bows down, with water collecting at the forward end of the cockpit. As I carry more ground tackle than normal, for cruising, and as the hull was designed to race with three up, I'm probably a bit light at the stern. I wouldn't want to put the batteries further forward.

    The Haswing comes with 4AWG/25mm2 cables, with a length of about 1.9metres built into the motor, then an Anderson connector, then a further 0.8 metre with ring terminals for the battery connection, in the normal open fishing boat usage. I will put in a 150A circuit breaker at that point, and  then I need a further 1 metre to reach the batteries under the cockpit. That 3.7 metres sounds like a reasonable length to me, for 25mm2 cable, and I'll hold off going up to 35mm2 for the moment. The voltage drop at full power is 2.64% according to this calculator.

  • 12 Mar 2020 20:05
    Reply # 8823958 on 8809939

    I don't know how this boat will sail and, for that matter, I don't know if my mental attitudes will have changed much in the five years that I will have been building her.  I might want to motor for more than 2 hours; I might want to motor sail.  I am watching with interest and, as ever, am astonished by your ever-agile brain, David, but for me I still see it as too much input and not enough out.  The time will undoubtedly come when I shall happliy convert to electric, but I don't believe that the technology has come of age.  For that matter, it's hard to justify buying all these new goodies, which have used a lot of resources to make.  I would have to use a lot of petrol to produce the equivalent carbon footpirnt.

    However, I can understand the intellectual challenge and the simple curiosity to see how it will work.  I am following this story with great interest!

  • 12 Mar 2020 19:19
    Reply # 8823850 on 8823175
    Jim wrote:

    Oh dear, what have I done!? well, David, we will be watched. :-)

    It doesn't make economic sense to me either. I just feel compelled to do it. I think it's hard-wired in my DNA.

    For both of us it's an interesting project, rather than an essential change. You had a working diesel, I had a working outboard.

    Hey, someone has to be first! Not so long ago, electric cars were rare, and not very good. Now, the Powers That Be want everyone to be driving one within a decade or two. Boats will go the same way, as the technology improves.

  • 12 Mar 2020 17:03
    Reply # 8823559 on 8809939

    This looks like another interesting project David, I've been playing it though my head as I work on Leeway.  I have two thoughts, largely related to the projects I've been working on, rather than of real importance to what you're doing.

    On a boat Weaverbird's size it is difficult to fit a lot of solar and one large panel might be as good as any compromise.  We just finished purchasing solar and I came to the conclusion that the number one problem was shading, even just a few shaded cells essentially knocks out the entire panel.  The flexible panels and controllers we looked at were also largely priced by watt, such that several smaller panels and controllers were the same price as one equivalent large one.  Smaller panels and controllers allow you to dedicate a single MPPT controller per panel.  Thus, if one panel gets slightly shaded, the other still has full output.  Controllers used to be much more expensive, the drop in price makes this kind of system more attractive.

    It would be nice to be able to generate power under sail in addition to solar.  You don't mention a wind or water generator, given your extensive experience you probably have a reason for this.  I don't really care for the noise of wind generators, and their of limited use if you like protected anchorages, but I wonder if there might be some merit in a water generator to ensure that you arrive with more charge in the batteries?  It doesn't look like the Haswing would be easy to turn into a generator, and that might be just as well given the backwards prop is going to be fairly inefficient as a generator.  Before the advent of cheap solar, water generators seemed to be more popular.  Do you have any thoughts on their utility?  I have a half-baked plan to make one out of a hoverboard motor and use some photogrammetry to mirror a prop with the 3D printer to see if I can make an efficient matching prop.  Admittedly, a good part of the motivation for this project is to have an interesting build with my sons.

    We had a Hurley 20 that came with a 80lb, 9.9hp power motor, when it died we temporarily used a featherweight 2hp evinrude and then a British Seagull.  The boat was far happier with either of the two lighter motors on the stern.  If it weren't for the cloud of smoke, I'd of been entirely happy with the Seagull. In many ways, the Haswing is an electric British Seagull.  It might be beneficial to mount the batteries far enough forward to keep the weight out of the stern.  I wonder if it might make more sense to put the batteries under your setee berth.  Although batteries close to the motor is nice, some heavy gauge cable can overcome distance and it would be nice to take the weight out of stern, maybe less so with the broader stern of a Hunter Duette than I experienced with the Hurley 20.  Although tinned cable is best, I pulled a lot of old untinned welding cable out of Leeway during the refit.  Despite some shoddy installation practices, it was all in excellent condition.  Sealed with some glue-lined heatshrink, welding cable might make an inexpensive way to move the weight of the batteries  out of the stern.

    Looking at the photo of the Haswing, it looks like they might have done what so many manufacturers do, which is to put wires that are too small for the rated current (sized by max ampacity of the wire, rather than for a low voltage drop) in order to save a few bucks in production.  I'd check the wire size and maybe it would be worth replacing the wires on the Haswing while you're still in the comfort of home.  Sizing for 3% voltage drop will give you higher output power, less wasted power and make you less likely to damage the motor (amperage increases as voltage drops which risks overheating).

    Looking forward to hearing your results.

  • 12 Mar 2020 14:24
    Reply # 8823175 on 8809939

    Oh dear, what have I done!? well, David, we will be watched. :-)

    It doesn't make economic sense to me either. I just feel compelled to do it. I think it's hard-wired in my DNA.

       " ...there is nothing - absolutely nothing - half so much worth doing as simply messing about in junk-rigged boats" 
                                                               - the Chinese Water Rat

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