I replaced a wonderful old WWII GM 271 stink-shaker with an old DC GE 120v 23hp/100peak motor on my 17 ton 55' Marco Polo, though with no generator and no parallel diesel ICE. Great for silent tacking assist, quiet morning marina maneuvering, and plenty of thrust, but even with 20 6v deep cycle lead acid batteries (12kWh bank), I did not have the luxury of distance (10 slow miles in calm conditions).
I also joined others in worrying about providing a continuous source of ignition (the DC brushes) down where explosive gasses could congregate.
I also lamented the comparative inefficiency of feeding hungry field coils on my DC motor, versus DC and AC motors with permanent magnets.
If you are going to leave the dock with only a quart of fuel (your 11.5kWh bank 70% discharged down to 30% remaining) you might as well use that fuel efficiently. AC travels through wires much much more efficiently, and the bonus of not exploding is pretty sweet too. Plus electrocution is much much more survivable with AC.
So the old industrial DC motors are great, but the newer AC ones (and similarly the permanent magnet DC motors with very short cable runs) go much farther with a higher probability of arriving alive.
Mark Stafford, e-GEO, e-scooters, e-kayak, e-sailboats, e-Leaf
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Posted by: mstafford@natca.net
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