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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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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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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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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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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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Discussion Starter · #24 ·
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...
I was planning to use Nissan Leaf EV batteries. They should be as good or better as any other Lithium battery out there.
 

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Discussion Starter · #25 ·
Well, I'm no expert, but that strikes me as a rather 'optimistic' outlook, to say the least…

:)
When I say "not a lot of cost" I mean "considerably less than it costs today". Between the density technologies that are coming online and the huge spike (as in, double to triple) in global manufacturing expected in the next 5 years, most of which is in the US, I expect domestic prices to drop quite a bit.
 

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Discussion Starter · #29 ·
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?
I understand where you're going with this. You're going to maximum battery lifetime, which is an important consideration most of the time.

However, I'm an engineer, and I like to look at the worst case scenarios. So let's assume I'm not an idiot and use a proper Lithium BMS with a cutoff of 20%. Any lithium battery should be able to discharge from 100% to 20% at least 1000 times, and most advertise far more than this. So, using my proposed setup, I'd have to be at cruise speed for about 2H to get down to 20%. So let's assume I'm an avid sailor and I go out as often as I can, every weekend for 6 months of the year. That's 52 days a year. 1000/52 = 19 years before the batteries are worn out.

I'm told the average engine wear per year is 50H, btw, so even my conservative worse case is an order of magnitude worse than what reality is likely to be.

Hell, if I get HALF that much life out of the batteries, that still gives me 10 years of diesel free sailing.

Please feel free to point out if any of my assumptions are wrong, or if I've missed something. I like to be thorough.
 

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Discussion Starter · #32 ·
^^^^bingo...

Im back in the states, soon to get a boat... Im all in the forklift conversion crowd that has been around for a long time now in the small sedan car conversion industry...

forklift dc motor, reostat...batteries

golf cart conversions are even cheaper, however those motors are more stop and go design and need cooling of some sort.

doesnt get any simpler than that and much cheaper than a complicated ac kit which has the unbenefit of being complicated to replace(especiaally fried controllers and chargers)

however there are some nice kits from electricmotorsport and other places that have awesome ac kits with regen.

my dream still for my future cruising boat despite the range defficiencies is to use 48v solar with portable gen backup, stepped down to house 12v.

48v for the electric inboard and 12house stepped for everything else...

no ac anywhere in the boat, shoreopower or otherwise

I truly hate ac heavy boats...that rely on conversion and inverters more than direct sources, i.e wind, solar....engine...etc...

anywhoo

time will tell
If you get a bigger DC motor than you need and run it at less than it's rating, you'll never have to worry about heat.

I like the Electric Yacht kits here: DIY Kits | Electric Yacht
I met the guys who sell their stuff here at the Annapolis boat show. They were very knowledgeable, and their primary engineer converted his own boat. When the time comes to do my own conversion, I'll probably end up using one of their kits to do it.

I'd also like my boat to be all DC, with a shore power charger if I need it. But I'm not doing a liveaboard yet, I'm still just a weekender. That might change when I move up to my next boat, probably a cat...
 

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Discussion Starter · #46 ·
Hi Guys. I'm purchasing a hunter 29.5, so I'm going to have to rethink my repowering strategy. The good news is the Yanmar diesel in the boat is in pristine condition, so I should be able to sell it for more than enough to do the conversion. Once I have the boat in hand I can start planning out the conversion. I'll probably start once the season ends, I don't want to take away my family's time on our boat during good weather.
 

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Discussion Starter · #48 ·
So why replace it? Electric will both reduce range and resale value. A diesel in good condition will have lower long term running costs than electric's periodic battery replacement I would think as well.
I'm not going to be using lead acid batteries, I'm going to be using LiFePo4 cells. Their lifespan should be at least 10 years, vs 5ish for lead acids. They're also considerably lighter (60lbs for 2kWh vs 400lbs). I'll no longer need a starter battery. I'll have a little honda generator for backup if I need it.

The electric motor will be about 60-70lbs, vs the 250+ for the diesel itself. It doesn't need any cooling, provided you run the motor at or under it's rated power. When under sail, I can regen some power back into the batteries.

So, the benefits are:

Less weight
No maintenance
Instant power (no warm up)
Quiet
No diesel smell
Amortized cost of batteries is low
More batteries can be added later
Power is cheaper than diesel
Regen when under sail
No house batteries, just a DC to DC converter

The downsides:
Up front costs are higher
Lower range (can be mitigated with more batteries later)
Requires an understanding of electricity to build a system, but not to run it.

The way I look at it, battery costs drop about 7% per year. If, at the next of next season, I feel that I need more range, I can drop in another set of batteries and add to the stack. I don't need huge range, I just need to get out of the marina and back. A friend of mine converts boats, and he says a typical monohull of my size runs about 750W of draw to go 3kts, which is about as fast as the marina lets me go anyway.
 

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Discussion Starter · #50 ·
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
I think you're assuming that I'll be running a 12V system. It will be 48V most likely, or 72V if I go with a bigger motor. That changes the cable calculus quite a bit. As a rule, I generally go with one step higher than I think I'll need.

Also, LiFePo4 batteries, amortized over their lifetime, are cheaper than lead acids are now for the same usable charge. Here's the math:

LiFePo4: $500 per kWh x 80% useable = $600 per useable kWh, /10 year lifetime = $60 per kWh/year
Lead Acid: $266 per kWh x 50% useable = $532 per useable kWh, /5 year lifetime = $106 per kWh/year

LiFePo4 batteries don't explode, even under the most extreme conditions. You're thinking of Lithium Ion batteries, which is an entirely different chemistry.

Since I can do the work myself, and sell my existing Yanmar, I can probably do the entire conversion for the value of the diesel on the open market, possibly a bit more.

Plus, I can always add capacity later on if I find I don't have enough battery for my propulsion needs.
 

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Discussion Starter · #51 ·
LiFePo4 batteries have not gone down in price recently - gone up as a matter of fact.

I can understand switching if the diesel is shot but to replace a good diesel with electric and get less range and resale makes no sense.

A well maintained diesel doesn't smell.
Funny, I haven't seen prices go up, and I monitor them pretty closely. Where are you sourcing your batteries? I'm generally seeing them for around $450-$500/kWh for the CALB Prismatics.
 
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