update on power consumption for electric 22' C-Dory cruiser

Tom Hruby

The summer is pretty much over for us and I have put WATT NOW "to bed" for the winter on its trailer. We spent a total 19 days on the water this summer of which 11 days were overnight. This has given me a good idea on how much electricity I use under a variety of conditions. With just my wife and myself, we cruise at about 5.1-5.3 mph and use 2.0 - 2.2 kW of power (~1 - 1.1kW per motor). Maximum speed is 6.8 mph at 5.8 kW total. With my entire family (4 adults and two kids) and their camping gear we were using 2.4 kW and traveling at 5.3 mph in calm conditions.

This confirms the estimates I made at the beginning of the season. The most energy I have used in a single day before recharging is 35% of total capacity (ended with 65% SOC -state of charge). I was able to recharge this amount in less than 4 hours from shore power.

My batteries hold a total of 20kWhours of energy so my initial estimate of 45-50 miles on a charge at cruising speed has held up.

Roamad · Posted: Sat Oct 12, 2024 8:11 pm Post subject:

Thanks for the update! Can we assume this is based on running both motors? What sort of speed/range might you see with just one motor?

Tom Hruby · Posted: Sun Oct 13, 2024 3:33 pm Post subject:

Yes the data I report are based on using the two motor simultaneously. When I run at 5 mph I am putting 1 kW into each motor. Since each motor is rated at a maximum of 3kW I could potentially cruise at 5 mph by putting 2 kW into only one motor. I have not tried it but I expect that it would be less efficient to do so. First, the motors are offset from the center line so if I was running on one motor I would have to slant to the motor to compensate for its off-center position. Second, running at 2kW would increase the rpms of the prop, and at slow speeds the efficiency of the prop drops as the rpm rise.