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Electric repower ideas

10202 Views 50 Replies 15 Participants Last post by  Captain Canuck
Hi Guys,

My wife and I have been researching how to repower our boat. This is for a number of reasons.

1) I'm an engineer.
2) We both hate the smell of diesel.
3) We are Chesapeake Bay sailors, so we only need the motor to get in and out of the marina.
4) We like to be eco friendly.
5) Diesel prices aren't ever going to go down, and solar power and regen is free.
6) We like the idea of a maintenance-free motor.
7) Net weight loss (with LiFePo4 or Lithium Ion batteries)

We have a 1987 Hunter 28.5. The 16HP Yanmar Diesel is nice enough, but for the Chesapeake bay it's probably overkill, and I can sell it to help finance the new system.

Here's the setup as I have envisioned it so far:

5 or 10kW DC electric motor w/regen
5 or 10kW DC electric motor controller
Lithium Battery Charge controller
6kWh of Lithium EV batteries
DC to DC converter for house current (negating the need for house batteries altogether)
200W-ish single Solar Panel to top off batteries when not in use (200W of solar should generate 1/2 to 1 kWh per day during the boating season). If my calculations are correct, I won't even need shore power between the regen and the solar panel to keep the batteries charged.
I'm looking at a total weight of about 200lbs, including solar panel, motor, controller, batteries, etc.

If my calculations are correct, I'll only need about 2kW of draw to push the Hunter at no-wake speed to get out of the marina, giving me about 8-10x the power I need to get in and out on any given day, assuming no regen from sailing and no solar.


No maintenance
Motor, controller and belt MTBF exceeds expected boat lifetime
Instant power (or reverse power) at any time, in any weather
Fuel is free, as long as I don't use shore power
Electric system is considerably lighter overall (Lithium batteries are ~1/6th the weight of lead-acid)


Limited battery capacity (though this will only get better as batteries advance, and I can add more later)
Refueling is slow (though if I'm only sailing on weekends, this is irrelevant)
A lot of work to retrofit, but not difficult work, just time consuming. Getting the diesel and tank out is going to be the hardest part.

Anything I've missed?
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Hi Captain Canuck,

You are headed in the right direction with your plans. If you are planning to use lithium it's probably a good idea to use a BMS (battery management system) so you don't run the batteries down too low or charge them too high. When I repowered my 1976 Ericson 27 with electric I hoped the AGM batteries that I used would last 5 or 6 years. At that point I thought I would replace to batteries with lithium. I have yet to make the change (6 + years) but I'm in the process. I didn't see any mention of instruments (I may have missed it). A voltage reading for each battery (down below) and an ammeter/voltmeter at the helm are pretty much must-haves. It's amazing how a very small adjustment in throttle position can lower your current consumption and keep you moving at the same speed. Also the ammeter at the helm is critical for regeneration. I started a description of my system on the Ericson Yachts web site, I need to update it but it may be helpful Ep - Blogs - EY.o Information Exchange
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