Update on electric C-Dory

Tom Hruby · Posted: Thu Jan 09, 2025 3:27 pm Post subject: Update on electric C-Dory

Now that the boat is on its trailer for the winter I wanted to pass on notes to for those interested in converting to electric propulsion.

1. The four 48V 100AH batteries (in two banks) are charged by a 20A charger I placed in the "shelf" in the cockpit. I have found that chargers in a boat need to be at least IP66 rated. The one I have is IP 67. Chargers that have internal fans rather than exterior heat sinks fail within a year because of humidity even if they are in a cabin.

The charger plugs into an exterior grade power supply I wired into the "spare" circuit in the power panel installed under the starboard seat. Since I have two battery banks I plug each one separately into the charger using a 50A Anderson Plug. Wires from the charger to the batteries is 10 gauge. I have posted a photo in my album (WATT NOW) The red power cord is the 120 V line coming in from the shore power in our RV lot.

I have also added solar panels and the charge controllers are in the other shelf on the starboard side. I have two separate panels, one for each battery bank. The panels need to be manually plugged into the controllers so there is no chance of accidentally charging using both solar and shore power at the same time. Photo also added to album. The white box in front holds my Dometic fridge. [/img]

Tom Hruby · Posted: Thu Jan 09, 2025 3:31 pm Post subject:

chromer · Posted: Thu Jan 09, 2025 4:19 pm Post subject:

roverfanatic · Posted: Mon Mar 31, 2025 2:34 pm Post subject: Speeds/Range?

This may have been discussed already, but what speeds are you seeing with those outboards? Very interested in this project as we look for our first C-Dory.

Tom Hruby · Posted: Mon Mar 31, 2025 3:26 pm Post subject:

I have two 3kW motors which can easily get me to hull speed. I cruise at about 5.1-5.2 mph using about 2 to 2.1 kW. I posted a graph of my speed vs. power consumption in my album (WATT NOW). Maximum speed is 6.8 mph which uses 5.8 kW of power (my max). Since I have 20 kWh of energy in my batteries my range is about 45 - 50 miles on a charge. The slower I go, the more distance I can travel. Using the equations in Dave Gerr's propeller book I estimate I would need about 11- 12 kW of power to get on a plane.

The electric motors are much, much, more efficient than a gas outboard. Travelling at 5 mph I estimate that I use only 0.4 kWh of energy per mile. Using some of the numbers available on this site I estimate that someone travelling at 5mph using a gas motor would use at 4.0 kWh of energy per mile (assuming a consumption of 8 miles/gallon of gas).

Tom Hruby · Posted: Mon Mar 31, 2025 3:36 pm Post subject:

P.S. I see you live in Bellingham. If you are ordering a new C-Dory from NMI (in Bellingham) be sure to tell them you are interested in electric. They were very helpful and I was able to customize my build to accommodate the electric. For example, I was able to get a reduced price since I would not be needing fuel tanks, the hydraulic steering, and the other things needed for outboards. They were able to put in a cable steering at a reduced price. I installed by own throttles and gauges that came with the motors. The only extras I ordered were the shore power connection and the "high top" cabin.

The also helped me install the outboards when I brought them to the factory. There are pictures of this in my album.