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Discussion Starter #1
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.

Advantages:

No maintenance
Motor, controller and belt MTBF exceeds expected boat lifetime
Quiet
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)

Disadvantages

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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RE; #2 Fix the diesel leak? I never smell in on my old tub with it's new fuel system.
RE; #3 Do you row the boat in July and August?
RE; #7 fire danger with Lithium Ion batteries?

add; #8 we have unlimited funds
add; #9 how much and how large copper cables, terminals, etc
 

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I don't see any glaring issues. You seem to be reasonable about expected range and capability which is normally the major problem with these threads.

I would suggest getting a small 2kw honda generator for those times when you need to deliver the boat somewhere, but otherwise it looks reasonable.
 

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Discussion Starter #4
RE; #2 Fix the diesel leak? I never smell in on my old tub with it's new fuel system.
RE; #3 Do you row the boat in July and August?
RE; #7 fire danger with Lithium Ion batteries?

add; #8 we have unlimited funds
add; #9 how much and how large copper cables, terminals, etc
#2: Tried that. It must be a very slow leak somewhere I can't find. It's not fast enough to be obvious, just enough to smell.
#3: I have no idea what you mean by this.
#7: Nope. EV L-Ion batteries have a discharge rate far higher than what I'll need, even at WOT. I don't expect them to ever overheat, but I'll probably put a temperature monitor on them anyway just in case.
#8: Heh. 6kWh of EV batteries is currently about $1400, and almost everything else will be covered by selling the old diesel. It's the labor that kills you on projects like this, but I can do all that myself.
#9: From the batteries to the controller (which is attached to the motor mount) Probably #000. Once I compute the actual load and distance required I'll go one step up from recommended, because overkill is underrated. Same reason I use 20A Nomex in my house for the 15A outlets.

Good questions though. I appreciate the feedback, I might have missed something.
 

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Discussion Starter #5
I don't see any glaring issues. You seem to be reasonable about expected range and capability which is normally the major problem with these threads.

I would suggest getting a small 2kw honda generator for those times when you need to deliver the boat somewhere, but otherwise it looks reasonable.
Point taken about the honda generator. After the system is installed, if I find I'm using more power than I thought, I'll probably get one. Theory can be a lot different than reality...
 

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July August are dead air months not to mention heat and the need for some people to get out of the baking sun rather then sit and wait..and wait... for a breath of air.

I'd dig deeper for the fuel smell/leak. Tank could have seepage in the bottom.

It all seems like allot of work and effort just to get in/out of marinas when you have a perfectly good engine.
 

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You could start the conversion by removing the tanks. Inspect before proceding further. Some means of producing juice to limp home on might decrease the timid factor when venturing afar.
 

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Discussion Starter #10
July August are dead air months not to mention heat and the need for some people to get out of the baking sun rather then sit and wait..and wait... for a breath of air.

I'd dig deeper for the fuel smell/leak. Tank could have seepage in the bottom.

It all seems like allot of work and effort just to get in/out of marinas when you have a perfectly good engine.
Point taken in regards to the dead air months. We'll just have to see how that works out after our first season in a pure electric.

I have a fair bit of experience with ICEs in general, less with diesels, but it could be a small crack in the fuel line somewhere that's leaking just enough to let it smell. $5 says I'll find it when I pull the engine out and it will be somewhere obscure and/or damn near impossible to get to.

In short, other than fuel supply, an electric system is superior in every single way. It's cheaper, easier to diagnose, more powerful pound for pound, the fuel is cheaper no matter what the source, there's no maintenance, etc. Once battery capacity or a small, portable high energy power source is developed, diesels are toast, save for "vintage" folks. I'd prefer to be on the leading edge than the trailing edge.
 

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Discussion Starter #11
Do you foresee ever selling the boat?

Such a modification could really narrow the field of potential buyers...
I plan to keep the boat for at least another few years. I think by the time I sell it, electrics, if not common, will be much better known. Once people in general know how easy they are to handle and how much easier they are to maintain, demand will pick up.
 

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Discussion Starter #12
You could start the conversion by removing the tanks. Inspect before proceding further. Some means of producing juice to limp home on might decrease the timid factor when venturing afar.
We'll see. I don't anticipate having many problems getting home most of the time. Someone suggested having a small honda generator for an emergency, which is a good idea. I'll probably pick one up after the conversion is complete, just in case.
 

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Point taken in regards to the dead air months. We'll just have to see how that works out after our first season in a pure electric.

I have a fair bit of experience with ICEs in general, less with diesels, but it could be a small crack in the fuel line somewhere that's leaking just enough to let it smell. $5 says I'll find it when I pull the engine out and it will be somewhere obscure and/or damn near impossible to get to.

In short, other than fuel supply, an electric system is superior in every single way. It's cheaper, easier to diagnose, more powerful pound for pound, the fuel is cheaper no matter what the source, there's no maintenance, etc. Once battery capacity or a small, portable high energy power source is developed, diesels are toast, save for "vintage" folks. I'd prefer to be on the leading edge than the trailing edge.
The major problem with electric conversions is the range. Make no mistake about it, there is no technology we have or is even in the pipeline that will make electric vessels capable of storing more than a few percent of the usable power available in fossil fuels.

The useful energy density of batteries just isn't anywhere close to that of fossil fuels. To get the same range under power, for every pound of diesel fuel you remove you need to add back fifty pounds of batteries. This very quickly hits a practical limit of just 1-2 gallons of diesel fuel.


The reason I said you seemed to be reasonable is that your plan assumes just motoring in and out of the harbor. Much more than just this is a very different question.
 

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The major problem with electric conversions is the range. Make no mistake about it, there is no technology we have or is even in the pipeline that will make electric vessels capable of storing more than a few percent of the usable power available in fossil fuels.

The useful energy density of batteries just isn't anywhere close to that of fossil fuels. To get the same range under power, for every pound of diesel fuel you remove you need to add back fifty pounds of batteries. This very quickly hits a practical limit of just 1-2 gallons of diesel fuel.
...
This is exactly what stopped us in the end. When I asked questions I got quite a few snide comments along the lines of "but it's a sailboat!" Our reality right now is that we have to be at work on Monday morning. Having a limited range where we sail would mean we couldn't sail up the many tributaries of the bay and wander too far from our marina and risk getting "stuck" on Sunday morning when there was no air. We just can't decide on the fly to wait two days to be able to sail out. The manufactures backed what Stumble said about the ability to recharge enough to do a potential 6-8 hour motor. It won't happen with the solar or wind technology that's available. And it didn't make sense to us to use up the limited room left with a diesel generator. Plus it kind of canceled out the reason for going electric in the first place. Might as well just get a diesel engine. So we did.

That said, I understand that electric motors are more popular on the west coast.
 

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Discussion Starter #15
The major problem with electric conversions is the range. Make no mistake about it, there is no technology we have or is even in the pipeline that will make electric vessels capable of storing more than a few percent of the usable power available in fossil fuels.

The useful energy density of batteries just isn't anywhere close to that of fossil fuels. To get the same range under power, for every pound of diesel fuel you remove you need to add back fifty pounds of batteries. This very quickly hits a practical limit of just 1-2 gallons of diesel fuel.


The reason I said you seemed to be reasonable is that your plan assumes just motoring in and out of the harbor. Much more than just this is a very different question.
I couldn't agree more. Here's some quick math:

Current diesel consumption: .43GPH at cruise. 11.5 Gal tank = 26.7 hours continuous cruise
@ $4 per gal, $1.72 per hour cruising
Refuel time, 4-5 mins plus however long to get to the diesel pump and back.

Projected energy consumption of replacement motor at cruise: 2kWh
Required battery bank for 26 hours of cruising: 52kWh
@ 12.5c per kWh, 25c per hour of cruising
Refuel time, ~ 14H on 30A shore power, assuming no regen or solar while cruising

Is it possible to put 52kHw of Lithium batteries on a boat? Sure. At 24lbs per kWh it would take 1248 lbs of batteries, for a net add of about 800 lbs (the diesel, tanks, fluids, cooling, etc run about 500ish lbs). It would just be very expensive to do it at the moment.

If I needed to cruise the boat for longer than a couple of hours, I would bring aboard a small generator with a 30A connector and run that every couple of hours to recharge the batteries. I don't see myself needing that very often, but it's a lot cheaper to buy a $1200 generator than an additional $10,000 in batteries.

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.
 

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Discussion Starter #16
This is exactly what stopped us in the end. When I asked questions I got quite a few snide comments along the lines of "but it's a sailboat!" Our reality right now is that we have to be at work on Monday morning. Having a limited range where we sail would mean we couldn't sail up the many tributaries of the bay and wander too far from our marina and risk getting "stuck" on Sunday morning when there was no air. We just can't decide on the fly to wait two days to be able to sail out. The manufactures backed what Stumble said about the ability to recharge enough to do a potential 6-8 hour motor. It won't happen with the solar or wind technology that's available. And it didn't make sense to us to use up the limited room left with a diesel generator. Plus it kind of canceled out the reason for going electric in the first place. Might as well just get a diesel engine. So we did.

That said, I understand that electric motors are more popular on the west coast.
I completely understand your point. Also, at the time you were looking, the technology was less robust than it is today. Your only option at the time would have been lead-acid batteries, which are finicky, have crappy capacity and are very heavy. Lithium batteries are much more robust and the prices have dropped by about half in the past couple of years, which changes the equation quite a bit. In the system I'm looking to install, I'm actually going to save weight on top of everything else. I still won't have diesel range, but I will have at least a couple of hours at cruising speed, and I can have a little (1600W) honda generator for the times I get becalmed should I need it. Hopefully, by the time I sell the boat, capacities and prices will be as such that a simple battery retrofit will get me much closer to diesel range for not a lot of cost.
 

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I completely understand your point. Also, at the time you were looking, the technology was less robust than it is today. Your only option at the time would have been lead-acid batteries, which are finicky, have crappy capacity and are very heavy. Lithium batteries are much more robust and the prices have dropped by about half in the past couple of years, which changes the equation quite a bit. ...
This was two years ago. We would have used Lithium batteries.
 

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Discussion Starter #18
This was two years ago. We would have used Lithium batteries.
Two years ago lithium batteries were around $800-$1000 per kWh.

Today, they can be had for ~$300 per kWh if you know where to find them.

I expect them to drop below $100 per kWh in the next 3-5 years, making them as cheap as lead-acid.
 

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theres a guy at my yacht club that purchased a brand new catamaran with 2 electric powered motor for propulsion in and out of the harbour. lets jsut say after 2 year i never seen anyone rip something out so quick. It may look good on paper but when it comes together you might have some issues. I would defiantly look at one of those new inverter generators that creaats enough power to run the electric motor because it will never charge your battery bank quick enough. have it run so you can switch it from charge to direct power. you can actually moun them in your engine compartment and weld up an exhaust to vent it. If your looking for wire. Consider using welding wire. It comes in every size and is pure copper.
 

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Canuck,

You need to redo your consumption numbers. The correct comparison between a diesel burning .4gallons/hr is about 6.7kw, not 2 (the actual number is 18hp/gallon). This is why renewables for propulsion power just don't work. Moving a multi ton vessel around just burns more power than any reasonable renewable setup can produce.

This is why it's critical when considering an electric setup that usage patterns change. You have to accept that you will go slower, with less range, and have almost no reserve power. So long as you are realistic about this it is fine, but fudge these numbers and you will be greatly disappointed.


As an addendum, there is no battery technology on the market, or even in laboratories today that come close to resolving this dilemma. The best laboratory battery I know of has an energy density of about 5% that of diesel fuel. This would still only provide a fraction of the power available most boats consider minimal. At the rate battery technology is going a realistic timeframe is probably more like 50 years (absent a real breakthrough).
 
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