electric Seawind 1000 XL2

[CatLove]

Originally Posted by toolbar

Ignoring range/capacity(!), the weight difference in weight does not seem that big.

2* Yamaha 9.9HT 90kg
2* Mechanical Throttle Control, Push/Pull cables 8kg
2* empty plastic tanks, gas tubes, 8kg
2* a bit of fuel 10kg
2* starter batteries 30kg
-> 143kg
(throw in a watt+sea generater at 9kg to get the hoped-for regen...)


2* Epropulston Evo 6, 72kg
1* 48v 280ah battery bank, 90kg
1* cables+electric control, 2kg
1* battery cable 5kg
-> 168kg

(only the major weight were researched, others are guesstimates)


I know about the TRT that reverted to burning fossils. But I wonder what the problem was.

Paul

Which Epropulsion battery bank is that ? Looking at their website none of the models could be combined to achieve 280Ah and 90kg weight or come close to it. They show 175Ah, 163, 80, 60 and 40Ah.

Do they have different battery models in Europe than here in the US? If so, I hope they will make these available here as well , especially if they're lighter weight.

[Statistical]

Originally Posted by CatLove

Which Epropulsion battery bank is that ? Looking at their website none of the models could be combined to achieve 280Ah and 90kg weight or come close to it. They show 175Ah, 163, 80, 60 and 40Ah.

Do they have different battery models in Europe than here in the US? If so, I hope they will make these available here as well , especially if they're lighter weight.

Pretty sure he is using his own (non epropulsion) batteries. While EP will happily sell you batteries all but their smallest model work with any battery of sufficient capacity and proper voltage.

[CatLove]

Originally Posted by Statistical

Pretty sure he is using his own (non epropulsion) batteries. While EP will happily sell you batteries all but their smallest model work with any battery of sufficient capacity and proper voltage.

Not really, unless by "work" you mean only propulsion but no regen. Given cat speeds regen is important as it can match or exceed a relatively large solar panel array.

[Statistical]

Originally Posted by CatLove

Not really, unless by "work" you mean only propulsion but no regen. Given cat speeds regen is important as it can match or exceed a relatively large solar panel array.

Good point although yeah I think that is the case. Pretty crapp for ePropulsion to do that. There is no good reason well no good technical reason. The motor controller will almost certainly be capable of regen so they are just locking it down for sales.

[donradcliffe]

Originally Posted by CatLove

Not really, unless by "work" you mean only propulsion but no regen. Given cat speeds regen is important as it can match or exceed a relatively large solar panel array.

Don't waste as much time and money on regen as Jimmy Cornell did.

https://cornellsailing.com/2020/12/electric-shock/

[Statistical]

Originally Posted by donradcliffe

Don't waste as much time and money on regen as Jimmy Cornell did.

https://cornellsailing.com/2020/12/electric-shock/

I think he just had asininely overly optimistic targets likely goosed on by the manufacturer to lock in a premium contract. He hit 500W of regen on the first leg and averaged 350W over the route.

350W * 24 hrs = 8.4 kWh produced per day. 99.9% sailors would be beyond estatic about that. That is like almost 2 kW of solar panels.

Even his targets show a naive misconception of basic math. The targets were 600W @ 6 knots and 800W @ 8 knots. Neither were hit but the two numbers together are completely impossible. Power generation is at the cube of velocity. If 800W @ 8 knots is correct it would only be 800 * (6/8)^3 = 337W at 6 knots. We aren't even getting into implementation details that is just basic math.

They also chose to go with only one servoprop and were encourage by early overly optimistic short trial runs. Had they gone with two servoprops instead by my math they would have averaged 550 instead of 350W. That would be 13.2 kWh of generation daily.

In fairness to Outremer I must point out that CEO Xavier Demarest, general manager Stephane Grimault and head of the design office Stephane Renard all advised me to have an auxiliary generator, even if only to be used in an emergency. But I refused, as it would have defeated the very concept of a zero emissions sailing boat. Only now, with the wisdom of hindsight, do I see that what they regarded as a possible emergency situation, sooner or later would have become the norm.

100% electric may not be viable but had he listened to people a mostly electric system likely would have been. A bit more solar, being lighter on the motor use and having a generator to provide sosme of the power it would be perfectly viable. Granted not the headline producing around the world with zero emissions but still impressive.

[aybabtme]

I'll address multiple posts at once.

• Jimmy Cornell: I'm not in his camp of trying to do it with just regen. I think he didn't put enough solar at all, and should have had at least a small genset.
• Weight: I'm using my own pack because the ePropulsion ones are not the right shape, and too heavy. This comes up to about 90kg total. In addition, the old AGMs were taken out. Overall the weight is reduced from the original 2xY9.9 at this time, and I have a lot more power storage than before. The waterline is slightly higher than before, but not for long as I'm going to replace the two tiny 2x200W panels with 4x470W. I have an out of date weight-and-balance sheet at https://docs.google.com/spreadsheets...it?usp=sharing.
• Power and speed: I can go faster with my electric outboards (7-8 kts, weather varying, but 6.5 in the graph I shared in a short trial) than with the Yamahas, but of course not for as long (only 1h). Also I have a lot more control authority with the electric outboards. The dang Y9.9 struggled to put me to a stop to avoid a collision in a marina. Meanwhile the electric outboards are really toying with my boat.

Right now I'm not planning on adding a generator, but I'm on the fence about getting one anyways in case I need to motor for a long while. After I turn on regen and put the 4x470W of solar, I'll see if I need a genset. I have friends who so far are doing it 100% electric, and have a diesel genset and it's collecting dust. I'm not as much a purist as they are, but I also don't want to have "the easy way out" of just motoring whenever things aren't perfect. I really enjoy how much more I sail with the electric drives than I used to. So all in all if I end up getting a genset, it'll be a small portable gas one like the Honda EU3200i. With a genset, my goal would be to be able to motor at 3.5 to 4kts continuously. Math suggests that a EU3200i would give me more range than the original Y9.9s, mostly due to better overall efficiency. If you add solar to it, then I don't doubt it.

[catsketcher]

Hello Antoine

Congratulations on your setup. I really liked looking at your graph on speed and power use. I have always been interested in electric but still use petrol outboards.

I was wondering if you tried to increase the size of your props to improve efficiency. One of my slight bugbears about my nice Yamaha big foot outboards is that they swing only 12 inch props. If I could swing a 17 inch prop it would sweep double the area, so I would only need to push the water half as fast backwards. That is more efficient because the amount of kinetic energy is the mass x velocity squared.

I think this is one reason why diesel boats get much better fuel economy than petrol outboards. Anyway, my thoughts were, did you try to go far down this road and use really big props at low, but still high torque (because electric have high torque at a wide rpm) speeds?

cheers

Phil

[sailingharry]

Nice writeup! And congratulations on not buying the bs about electric HP being better than ice HP. HP is HP, and you installed very close to what you took out.

[donradcliffe]

[QUOTE=Statistical;3773721] Power generation is at the cube of velocity. If 800W @ 8 knots is correct it would only be 800 * (6/8)^3 = 337W at 6 knots. We aren't even getting into implementation details that is just basic math.

/QUOTE]


Power usage is also the cube of velocity, so it would be very interesting to plot the cube root of the data in post #1. Unfortunately, I am stacked up with other projects today.

[Statistical]

[QUOTE=donradcliffe;3774696]

Originally Posted by Statistical

Power usage is also the cube of velocity, so it would be very interesting to plot the cube root of the data in post #1. Unfortunately, I am stacked up with other projects today.

Not sure what you mean by the cube root but his data does pretty close track the hypothetical.

At 3.6 knots he uses 2kW.

So using the cube law in theory at 6.6 knots he should use
(6.6/3.6)^3 * 2kw = 12.3 kW which is roughly what his observed data shows (12 kW).

As a hypothetical if he wanted to go faster and bought larger motors how much power would it require

At 8 knots it would require
(8.0/3.6)^3 * 2 kW = 21 kW.

While power goes up by the cube of velocity you are also going faster so energy consumption per mile goes up by the square.

At:
3.6 knots = 550 Wh/nm
6.6 knots = 1877 Wh/nm
8.0 knots (projected) = 2743 Wh/nm

This is largely why it is only sailing vessels that are just barely getting to the point where EP can work (with some accepted limitations). First some portion of mileage is by wind which helps. How much depends on the sailor but it isn't 100% by propulsive power. Second is sailboats are relatively slow and energy consumption increases by the square. Even if wetted area and displacement were identical a motor yacht doing 20 knots isn't using 4x the energy per mile as a sailboat doing 5 knots it is using 16 the energy. It would need a battery bank 16x as large for the same range.

[PineyWoodsPete]

[QUOTE=Statistical;3774706]

Originally Posted by donradcliffe

Not sure what you mean by the cube root but his data does pretty close track the hypothetical.

At 3.6 knots he uses 2kW.

So using the cube law in theory at 6.6 knots he should use
(6.6/3.6)^3 * 2kw = 12.3 kW which is roughly what his observed data shows (12 kW).

As a hypothetical if he wanted to go faster and bought larger motors how much power would it require

At 8 knots it would require
(8.0/3.6)^3 * 2 kW = 21 kW.

While power goes up by the cube of velocity you are also going faster so energy consumption per mile goes up by the square.

At:
3.6 knots = 550 Wh/nm
6.6 knots = 1877 Wh/nm
8.0 knots (projected) = 2743 Wh/nm

This is largely why it is only sailing vessels that are just barely getting to the point where EP can work (with some accepted limitations). First some portion of mileage is by wind which helps. How much depends on the sailor but it isn't 100% by propulsive power. Second is sailboats are relatively slow and energy consumption increases by the square. Even if wetted area and displacement were identical a motor yacht doing 20 knots isn't using 4x the energy per mile as a sailboat doing 5 knots it is using 16 the energy. It would need a battery bank 16x as large for the same range.

The cubic relationship here has to do with prop dynamics: specifically, the power needed to spin the prop in water (Prop. Demand, or PD), which increases by the cube of the % increased or decreased. Eg, 2X RPM = 2(cubed)=8 when the engine speed is doubled, and if by 1/3rd, by 1.33-cubed=2.35X; or reduced by 1/3rd, 0.66 cubed = 0.29X. This is purely a calculated relationship, and depends only on knowing your motor RPM @ WOT and lesser speeds, regardless of reduction ratio. It correlates quite well with fuel consumption, or in electric motors, I assume kW draw.

[Icarus]

Good for you...

[toolbar]

@aybabtme: any update on the regen-front?

Paul

[aybabtme]

I was working on it while also upgrading my solar, but finished the solar upgrade first and it's generating so much extra power that I lost motivation to finish the regen part.