Sunday, November 2, 2014

Power Supply

I'm still not happy with our electric motor. Well, the motor is great, but storing electricity to run it is a pain in the neck. Whoever can engineer a more energy-dense storage method for a reasonable price will surely make a Brazilian dollars, some of them mine.

We bought a power supply box from an electrical supply store, and had it shipped to Sipsey's apartment in the city. This box, about a foot long, 3 inches thick and 5 inches wide, takes 120vac in and makes 48vdc out. Our little suitcase generator makes 1.6 kW, so we get about 30 amps of 48vdc power. There is an adjustment screw on the power supply, to adjust the output voltage.

We ran an exterior grade 12awg extension cord from the 120vac plug on the generator to the power supply. Then from the 48vdc we go to a switch. The switch has inputs from the battery bank and the power supply. The switch outputs to the motor.

Somehow the dealer for this product doesn't include the mounting brackets with the box itself. They are sold separately, cost $.50 each, and were out of stock when I ordered. Argh! So instead of having the perfect parts for $1.00, I bought a stick of aluminum for $12.00 and had to make it myself. Grrr. The stick of aluminum wasn't quite big enough, so I had to use extra nuts as spacers to get the bracket to hit both the wall and the mounting holes in the power supply. They are held on by bits of tape so they'll hold still while we install it.
Heaven forbid, I actually put it together correctly (though I won't show you the final installation until I fix a few cosmetic errors that a real electrician would have a fit over). We fired up the generator, and it made the motor work! Though, of course, I had the voltage up too high (still well within the motor's limits), and overloaded our poor little generator. That was kind of exciting, since we started drifting towards the mooring field. We switched it to battery power, picked up one of the tons of free moorings offered by Port Washington, and troubleshat. I shortly decided the power supply was asking for more power than the generator could create, and the generator stopped making power. So we simply restarted the generator and all was well. I also found out that if I drop the throttle quickly it turns off the power supply, but if I bring it down slowly it's fine.

This is the lowest cost option for long duration motoring on our boat. We have considered many options, and this is probably not the longer term solution, but it is sufficient for right now. Other options have included more batteries, lithium batteries, an outboard, a 2nd generator, a diesel generator, or a new diesel engine. Does anyone have a different option we haven't considered? I"m pretty sure we've got the pros and cons of these options pretty clear.

Moore Better Later


  1. Phew!! I'm exhausted! ..need a "nap" after catching up on your last few posts! (and I still remember asking ...what will you be doing to pass the time?...LOL!!) I remember my trip to Lady Liberty on the Ferry..very busy out there!!! WOWIE!! is right!! you guys are to be congratulated for your navigation skills!...with currents dictating your movement, yes, you are truly "Living in the moment"....Much Love...Aunt Bev

  2. Nate, I liked hearing about your new power supply. I also liked your comment regarding "other options considered" and, reading between the lines, that no further advice is desired on that score! My recent input may have had something to do with the comment, so...point taken! All the best, Dana

  3. Hi Nate, I vote Diesel generator. It's something I've given some thought with your electric motor setup. Here's why ... assuming you have your boat for a while, and assuming the future of boat motoring is electric (I think it is, because the torque curve of electric motors are exactly what displacement hull boats like yours need) then it's basically a waiting game for the efficiency/cheapness of batteries, photovoltaics, wind buggers, etc., to catch up to the efficiency of the electric motors. So it makes sense to stick with electric drive, BUT the generator gives you the stopgap solution. Diesel over gasoline because it's so much more stable as a fuel, I hate gasoline on boats. The volatiles boil off, gasoline is not good for long-term storage. You can put in a big diesel tank, fill it up with the cheapest diesel you can find (maybe even kerosene, depending on the tax-status and rules) and then not have the headache of having to row around five gallon jerry cans of gasoline for the rest of your cruising life. You also won't need to worry about a gasoline fire. I used to have gasoline on my boat, and it was a constant worry, the fiberglass hull of boats traps the vapor, again, so much lower vapor pressure than diesel/kero.

    The other options are difficult. A good diesel generator, controller and fuel tank may only set you back less than $3k. That will barely pay for a twitchy outboard strong enough to move a boat your size. Repowering is big, big bucks and then you lose the beauty of that electric drive system.

  4. I very much like this post! Thanks for sharing, I have one bought from