Electric Sailboat Conversion


New Member
May 11, 2022
Hello everyone, I am new to this amazing forum and just want to quickly introduce myself and my project.
My name is Christof and I am located in Vancouver B.C Canada. For the last 2-3 years I have completely rebuilt my storm-damaged 36' Sailboat and removed everything that was bolted on including the whole Diesel system. After exploring many options on propulsion we have decided to go electric.
And that's why I am here.
I am looking for some guidance and help to finalize my onboard electronic specifically the 48volt side of it, i have roughly sketched out (attached) what the system is going to look like and all the components in the drawings are on hand. The 20kw Electric propulsion system is made by Electric Yachts and is very straightforward, they have provided all the info and components to make the propulsion work.
The big question marks are wire gauge sizing as well as sizing the breakers and integration of a 12-volt house battery bank past the DC/DC converter.
We have 12x 100ah Battle Born Batteries which are paired in 3x groups to make 300ah @ 48volt. 4x Batteries are wired in series connected with 4/0 battery cables to make 48-volt and I am wondering if I can use 2/0 to parallel the 3 battery banks. How big does every Pre-Battery fuse size need to be i am assuming 100amp?
Is there an easy way to calculate breaker sizes and cable gauges?

Thank you in advance for any sort of info that comes my way I really appreciate it and I am looking forward to an amazing discussion around this topic.
I am very open to alternative solutions and ideas to improve the system.

If you are further interested in the major refit project you can DM me and I am happy to share the process.


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New Member
Oct 2, 2021
While I don’t have the knowledge to answer your questions Christof, I am very interested in your project. I have a 1976 36’ sailboat as well that will require a repower one day soon. I feel like cruising in the PNW is full of long passages without wind and so have thought the electric range is just not possible (we are further north up Vancouver Island). I’d be very curious to hear more about your plans and capabilities. What model of sailboat is it?


Solar Addict
Feb 11, 2021
Is there an easy way to calculate breaker sizes and cable gauges?
There are 2 considerations, current carrying capacity, and voltage drop.
For current carrying capacity, you add up or otherwise determine the maximum current you will pull. The motor manufacturer should be able to help there. Then find a chart that gives wire size vs current. That gives you a minimum wire size. The fuse needs to be smaller (in amps) than what the cable can support, so the fuse will blow before the wire fails.

The second consideration is voltage drop. Longer wire runs will cause a larger drop in voltage, and thus need to be sized to a larger wire. Tables for 48 volts are hard to find, but here is an explanation, and the formula to calculate it.