SailNet Community banner
  • SailNet is a forum community dedicated to Sailing enthusiasts. Come join the discussion about sailing, modifications, classifieds, troubleshooting, repairs, reviews, maintenance, and more!

Electric repower ideas

10225 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?
See less See more
1 - 2 of 51 Posts
Of course, this is based on today's prices. Lithium battery prices are falling like rocks, and with the new Tesla battery factory coming on line next year, I expect they will fall still further. So far, in fact, that lead acid batteries will be extinct if there's enough capacity to replace them by then. Certainly the technology will dead-ended by then, at the very least.
I have been pretty involved in the LFP marketplace for a number of years at both the build & install level, and US marine standards level, and I can say that the prices have not budged on quality prismatics.

What we do have now are a lot of el-cheapo Alibaba, unknown quality batteries coming out of China that you would not catch me dead installing on a boat.

You need to compare known quality brands of prismatic cells with known measurable histories such as CALB, Hi Power, GBS, Winston etc. If anything the quality brands are stagnant in pricing, or going up slightly. I used to be able to buy a 400Ah CALB SE cell for about $440.00 today the CALB SE cell is running over $500.00 & the 400Ah CALB CA cell running about $570.00...
I was planning to use Nissan Leaf EV batteries. They should be as good or better as any other Lithium battery out there.
Good luck with that.... Which BMS do you plan to use with those cells? These are proprietary cells which were designed for PSOC operation ? How are you going to mange cycling in the middle range for best cycle life?? How often between full recharges? How many PSOC cycles?
1 - 2 of 51 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.