I guess I am going that way, two identical drives, one heavy boat runs great, newer one at 1/2 the weight and same power, batts. Cruise, (forgot GPS!) is about a brisk jog, figure 5 hrs. at 20 ish amps, conservatively. Will publish more when done and have both on the water at the same time. Not exact of course, but could provide interesting data concerning weight and hull shapes. This all by accident of buying two power kits, and being a boat builder, building boats designed to be EV efficient is great fun.
later, Cal
Sent: Saturday, February 27, 2016 9:57 AM
Subject: [Electric Boats] Re: Efficiency
I believe your challenge to be somewhat unreasonable - who has two boats (or two drive systems) to dedicate to proving what they think they already know?
Something you have not thought about, is that resistance goes up rapidly with a rise in temperature, and temperature goes up with current, All things being equal, if your system uses a lower voltage to produce a similar power, it will draw more current, and run hotter. It will then be necessarily less efficient since it is wasting electricity to produce heat (which increases resistance, sometimes in a deadly run away effect).
Although electric motors produce decent torque at low RPM, they will run hot doing so. Your motor is rated at a certain continuous current based on its "ideal" RPM - in other words, its ideal effective voltage. Running the motor outside its sweet spot in terms of RPM for long periods will result in greater heat generation, and lowered efficiency.
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Posted by: "cal" <h20dragon@centurytel.net>
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