[omeriko]

Hello friends
True, this is not a car, but still, i think this is the forum to talk abuot it.
My brother and I decided to buy a boat as a pension way off life ..
me:
50 years old, looking for an adventure, a mechanic and a car electrician understand my way in electronics computers act.

After a few searches, we decided to buy a riverboat more than a century old
60 feet long and 11 feet wide
Currently with a DAF diesel engine ???hp, over 40 years old which take 7 liters per hour, and looks verry tired, expensive trip...
the conclusion?
we thought of converting the boat to an electric motor, and sailing relatively quiet.
Here I'm a little lost, which engine? Speed controller? Bank type batteries
I'm on a $3000- 4000$ budget
aimed for 7 knot sailing ability for 8 hours
Would love to work with second hand equipment
* What is your professional opinion?
Is this possible in this budget?
where to start?
thanks
Gunga & omeriko

 

[MattsAwesomeStuff]

60 feet long and 11 feet wide...
Currently with a DAF diesel engine ???hp, over 40 years old which take 7 liters per hour, and looks verry tired, expensive trip...
I'm on a $3000- 4000$ budget
aimed for 7 knot sailing ability for 8 hours
Is this possible in this budget?

Sadly, I'd say no. Not by a long shot.

I can't imagine moving a 60 footer at 7 knots for 8 hours on a battery pack you could buy for $4000. Let alone everything else.

Just doing some ballpark math...

1 - Your engine uses 7 liters an hour, and you want equivalent to 8 hours of range. So, 56 liters of diesel. That's an average-ish sized tank for a car.

2 - An average-ish car might get ~600 or so km on a tank that size. An average-ish car uses around 9L/100km.

3 - An average car converted to electric might use around 200 watt-hours per km. So to get 600km of range on an average car, you'd use 120,000 watt-hours of energy, so that's how big a battery pack you'd need.

4 - 120kwh battery is going to blow your budget by 5-10x.

5 - 120kwh / 8 hours = 15kw motor. That's your steady draw for your motor, so your motor should be at minimum sized for 15kw continuous duty.

6 - That's if you can charge 120kwh overnight every night, does river-way electric infrastructure support this?

7 - You don't mention where you're getting power from. Batteries store power, they don't generate it. Were you thinking solar? 60x10 = 600 square feet of boat ceiling. A solar panel makes about 15 watts per square foot, so 9,000 watts in peak noon sun. You need 15,000 watts continuously for 8 hours.

8 - Most places in the world have around 4-5 peak hours a day of solar. So, if your boat has a ceiling and you'd cover the entire ceiling in solar panels, you'd reach 40kwh of energy captured during a 24 hour period. You need 120kwh to get the range you want. So, even fully solar is only 1/3 of your energy needs (and at best 60% of your power needs, at noon, i.e. you'll never hit 7 knots ever, when directly driven by solar).

...

So, I'm not sure what you're imagining how you'll get power (shore or solar), and how much power you want to store, but, I'd say your budget is off by at least 10x.

That's not even counting motor and controller and all the accessories.

The good news is that if you're willing to give up some range, your costs will decrease about linearly with howevermuch range you want to give up.

And if you want to give up speed, your costs will decrease exponentially (quadratically?) with speed. I.E. Going 1/2 the speed uses 1/8th the energy.

 

[oren]

Thank you for your detailed answer.
Yes, a bank of 120kwh is out of the question
So, taking your recommendation for reducing speed and duration :
for cruising at 3-4 knots for 2-3 h a day we will need a bank of about 10-20 kwh ?

(btw, i don't know yet to what speed to expect from a continuas 15kw. but let's stay with that number for now).

As for recharging, We will likely stay off grid most of the time, and would like to charge with solar panels + a small generator. we have about 150 sq feet of roof.

 

[drother]

You might look around and pick up an entire EV for this conversion. Maybe a wrecked Nissan Leaf or Chevy Volt (would still need to source a motor is doing a Volt).

 

[MattsAwesomeStuff]

So, taking your recommendation for reducing speed and duration :
for cruising at 3-4 knots for 2-3 h a day we will need a bank of about 10-20 kwh ?

Very very roughly, and I don't know my boat stuff that well, I've only ever had this kind of chat with a boat engineer once...

Cruising at 3.5 knots instead of 7 knots should cut your power requirements down to 25%, and your energy requirements down to 12.5%.

So, cutting speed in half an instantly you only need 15kwh.

If you're only travelling 2 hours a day instead of 8 hours a day, linearly cut that to 25% again. So 3.75 kwh. There's E-bike batteries that big.

But also keep in mind you've cut your speed in half and travel duration to a quarter, so you're only getting 1/8th the distance in a day.

As for recharging, We will likely stay off grid most of the time, and would like to charge with solar panels + a small generator. we have about 150 sq feet of roof.

I'd say there's no point in running a generator if you already have a diesel engine. You might as well directly push the boat with the engine instead of run a genny to charge a battery to feed a speed controller to run an engine.

With 150 square feet of roof you can fit about 2250 watts of solar. With 4.5 peak hours a day, you'll have 10kwh of energy a day to play with. That's still 3x your energy needs for the day (meaning you could travel 3x as many hours [6], or, at efficiency loss, travel slightly faster). If you choose to travel for more time, you've taken your range from 12.5% of your goal up to 37.5% of your goal.

Another option is just directly driving the motors from whatever the panels are generating, not storing it or having batteries at all. (Or, indeed, having only 3.75kwh, so you can kick it a bit when you need to).

Perhaps it would be good inspiration for you to watch a million videos on Jamie Manzel's youtube channel. He's built 4 solar boats now, himself, generally from materials and garbage, with very few tools, in the middle of Panama. He is foolishly and deliberately ignorant about electronics and batteries (and boat design, and propellers), half due to arrogance that he knows better than the rest of the world, and half due to him just wanting to discover things for himself, so do not copy anything he does or take advice from him. He's often just flat out factually wrong, he refuses to listen to anyone's advice on why things don't work. Like, he refuses to use a charger (because electronics just break), he only wants to direct charge batteries from solar panels, and then applies lead-acid knowledge to lithium batteries, only ends up charging them 20%, and then spends a year building a whole new boat because he's not satisfied with his battery arrangement. Instead of buying a $40 charger.

But, just in terms of capability, you can see what he's doing. He has sworn off gasoline and be pedal-powered boats a trip to "town" is like 8 hours round-trip, and not too much faster with solar help.

https://www.youtube.com/user/JMEMantzel/videos

For help searching, his 3 boats are:

1 - "Shark Slicer", a heavy-ish barge-like boat to haul gravel and concrete for his projects (which he figured would be paid for in a year with how much cheaper it was to not pay for delivery). It's not even all that slow, but it is a bit clumsy.

2 - "Zombie Chopper", the smallest, a light boat that's supposed to be the fastest, to get to town and back as fast as possible instead of taking the previous one. It holds two people, but barely, and doesn't have much left over for cargo afterwards.

3 - "Solar Snailer/Sailer/Boat Chips", a rebuilt version of his first solar boat with a swivelling roof that didn't really work. Now has a trifold solar roof with a paddlewheel meant as a fast-ish 2-4 person craft for moderate cargo, since the previous boat wasn't practical once he started having other families settle near him. He's almost done this one.

Just for casual mention, he also built a mini-bulldozer, an island castle, a 6-legged walking 12' tall walking robot, a videogame, a 4 story geodesic dome with the third floor being a giant trampoline, tons of interesting stuff.

 

[theonetruerat]

Jamie Manzel is a fascinating dude.

 

[GregShay]

Matt posted a great set of ballpark math... Except for the fact that old diesel engine can be very inefficient. Using the energy equivalence of the fuel, is probably way too high.

I would start with some basic figures of power required to move boats (which I admit I know nothing about. But I imagine is readily researchable.).

Historically, (slow) water transportation is low power. A solar eBoat with some battery storage, *should* be in the ballpark of possible, I would think.

Greg