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Old 11-12-2018, 19:12   #1531
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Re: Oceanvolt Hybrid Motor

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Originally Posted by john61ct View Post
Personally I want to know fuel per mile.

Real world, pushing 8-10k lbs displacement monohull, say 20 miles over eight hours.

Direct drive vs genny+EP

And how heavy does the battery need to be to do that for say three of those hours?

And how costly for the EP vs the old-school direct drive?

And finally, how much solar panel wattage would be needed to contribute say 25% of that power, in a clear tropical solar day?

Sincerely would love to see those numbers.
You can easily do most of that yourself with a little web-surfing. But I'll kill some time.

I'll start by saying that to me EP is a lot less compelling on a monohull. The weight advantages aren't as meaningful or as significant when you're getting rid of one diesel instead of two and you don't have any room for solar.

Let's go with a Beneteau Oceanis 41.1 then. Smack in the middle of your tonnage.

So you've specified a cruising speed of 2.5kts. Let's assume no current. For that size of boat I would guess you'd probably get there with... oh something real small. 4kW? Let's use the Torqeedo Cruise FP 10.0 then. Underpowered for the boat in general, but it'll do the job you've asked of it and Torqeedo's site is easier to navigate.

Now you want to cruise at 4kW for 3 hours on battery alone. Let's throw in three Torqeedo 48-5000 batteries then. That's 109.5kg.

You're up to 143kg total now and about $24,600 out of pocket. Whatever existing generator you have will probably supply the 4kW you need, but let's say you'd prefer to be able to provide 80% of peak demands. You need 10kWh per hour then so an 8kW generator. With a full battery you'd have 15kWh / 2kWh == 7 hours of wide open throttle available then. I think I'd probably consider anything over 4 hours "continuous" enough for me, so I'd probably go with a smaller unit but weight, cost and fuel efficiency would be the deciding factors overall.

That math disregards solar input, but I think it's fair to plan around your worst case requirements. Assume you head out in the evening.

Battery weight isn't much of a concern unless you absolutely insist on LiFePO4. I think that's a bad idea for several reasons but this isn't a battery thread.

Like I said though, I wouldn't count on solar. You're asking for 3kWh (4kW * 3 hours * 0.25) of solar input. With 4 hours of good unshaded shine you'd need to pack 750w of solar in addition to whatever you needed for other loads. That's not a big number for a multihull, but I'm not sure it's a reasonable ask of most monohulls.

Your requirements here seem pretty reasonable and realistic overall to me. Except I'd want more power/speed. I'd probably go with an ElectricYacht 20kW motor on this boat recognizing I'm probably dropping my max speed to about 7kts. That changes the generator and battery only runtime of course, but still within comfortable margins if you're willing to slow it down a bit when running on pure battery power. I'd probably kick the generator up to 10kW. Maybe I'll do 5kts. Maybe 1.5kts going uphill with a drained battery in open water. As long as I'm still making headway.

It's not going to be the "budget" option anytime soon that's for sure.
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Old 11-12-2018, 19:19   #1532
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Re: Oceanvolt Hybrid Motor

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Originally Posted by transmitterdan View Post
Who cares if a 15HP EP can "cruise" at max HP. So can a 15HP ICE. But if you think electric motors and the inverter drive and genset can run flat out max HP in cruise mode for days on end and last forever then you have a rude awakening in your future.
Unfortunately, that is not correct. A normal 15HP ICE cannot cruise for longer than it's duty rating allows (warranty), and at that rpm and WOT is burning massive quantities of fuel.

EP can run at it's rating continuously, at least the manuals and spec's I have read support this. Elco is the only one I've seen that publishes a separate continuous and peak.
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Old 11-12-2018, 19:25   #1533
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Oceanvolt Hybrid Motor

Ok, let's stipulate a 20HP continuously rated ICE running at 15kW continuously. It will last thousands of hours. And where do you get the "massive quantities of fuel" by running at continuous rated HP? It should be near max fuel efficiency should it not?
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Old 11-12-2018, 19:30   #1534
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Re: Oceanvolt Hybrid Motor

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Originally Posted by bridaus View Post
Unfortunately, that is not correct. A normal 15HP ICE cannot cruise for longer than it's duty rating allows (warranty), and at that speed is burning massive quantities of fuel.

EP can run at it's rating continuously, at least the manuals and spec's I have read support this. Elco is the only one I've seen that publishes a separate continuous and peak.

So, as reported above, my ICE can cruise continuously at 89% of rated output. So a 17hp ICE can cruise at 15hp continuously. An EP running at 15hp requires a 17hp ICE to turn the alternator to deliver 15hp to the drive train.


Fuel burn is a loading issue, you'll burn more using ICE to power EP.



What is your argument?
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Old 11-12-2018, 19:34   #1535
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Re: Oceanvolt Hybrid Motor

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Originally Posted by transmitterdan View Post
Ok, let's stipulate a 20HP continuously rated ICE running at 15kW continuously. It will last thousands of hours. And where do you get the "massive quantities of fuel" by running at continuous rated HP? It should be near max fuel efficiency should it not?
20HP = 15kW, that's max. Keep going. What duty rating are you proposing?

In addition max fuel efficiency is at low RPM lots of throttle, so you will keep having to reach there too.

The reason you can't get here from there is the OEM's are not dumb, they are not making mistakes. They are sizing the engine optimally for their buyer's cruise profiles while marketing the max HP. They are not doing it wrong, they are just selling a product optimally.
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Old 11-12-2018, 19:36   #1536
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Re: Oceanvolt Hybrid Motor

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Originally Posted by 44'cruisingcat View Post
We're saying you'd size a diesel for CONTINUOUS HP.

It's just that some are claiming that continuous HP is about 1/2 the rated output. This too, has been proven to be dishonest. (It might be true for very large engines, but not the sizes we use in sailboats.)
I only care about HP inasmuch as I need a particular number to meet my cruising goals. From there it's totally unimportant.

The 1/2 rated output comes not because EP horsepower is "worth more" than diesel horsepower (whatever that's supposed to mean other than derating a bit for duty-cycle). It comes from the idea that a fuel efficient generator will provide the energy I need much more efficiently than a Diesel engine connected to the props rated similarly.

Because the diesel engine's rating is peak power where its very inefficient, while the generator should be producing it's rated power at its most fuel efficient.

I don't know how many more ways that can be said.

Either you understand that, but don't agree with sizing your power requirements like that. Which is totally your prerogative and doesn't make you wrong. Don't take it so personally! Powerboats aren't for me. That doesn't make them "wrong".

Or you're having trouble understanding it, but would agree with the premise. Or you don't understand it and I can't make you understand it. If that's the case, I'm sorry, but I don't think I have the vocabulary to help you out. It's me, not you.


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Originally Posted by 44'cruisingcat View Post
The EP faithful
"faithful". Comes off a bit whinging don't you think?

Quote:
Originally Posted by 44'cruisingcat View Post
1: That you can only run a boat motor continuously at about 1/2 power. Or less.

2: But if that same motor was bolted to a generator, then all of a sudden it's fine to run it at 90+% power continuously.
I'm pretty sure I've seen no one say that. I mean, the engines I used as an example earlier have almost 1L between them. Unless your goal is producing the most horsepower per liter I think you're a bit lost.

Quote:
Originally Posted by 44'cruisingcat View Post
3: That even though marine diesels are supposedly only good for 1/2 their rated power, you can replace them with electric motors of 1/3 the rated power because you can run the electrics at 100% all the time.

4: Then you can size a generator that might only allow the electric motors to run continuously at around 50-60%, (with the genset flat out) and STILL get equal performance.
No, that's obviously not the case. You could size up your generator, and still be more efficient, but I wouldn't. 50% seems about right to me. If I can run at WOT for a few hours I think that's a good benchmark. From there I'd be happy to run continuously, and fuel efficiently, while backing off a couple knots.

Quote:
Originally Posted by 44'cruisingcat View Post
So basically, they're claiming that a 12-13 kW diesel is equal to TWO 30 kW diesels, IF instead of connecting it directly to a propeller, you connect it to a generator which is connected to electric motors.
So I can choose to believe you've got some serious reading comprehension problems, or I can just accept you're just ungodly stubborn and no amount of explanation will ever satisfy you and I'm wasting my time.

I'm going to go with stubborn. You built your own boat after all right? That's pretty impressive. It's served you well. But I think I'd rather hash this one out with a brick wall at this point.
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Old 11-12-2018, 19:39   #1537
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Re: Oceanvolt Hybrid Motor

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Originally Posted by bridaus View Post
I can answer this one. About 50hp of diesel to match 15kW of EP at cruise.
Ah yes, that sad old Yanmar 4JH5E that is barely running at its lowest 1600 RPM while it only delivers 25 KW at the shaft is a good match for the 15KW EP. Gonna be a little rough running it that slow, but that's the least it can do.
Have you seen the gap between it's typical prop power curve and it's shaft power curve? You seem to be missing the fact that direct drive diesels are typically connected to FIXED PITCH props that meet up with the engine at max speed. This is so you can USE that extra power if you need to. Yes, a Leopard 46 is overpowered with two of these.
This feels like Groundhog Day.
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Old 11-12-2018, 19:40   #1538
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Re: Oceanvolt Hybrid Motor

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Originally Posted by OldMan View Post
So, as reported above, my ICE can cruise continuously at 89% of rated output. So a 17hp ICE can cruise at 15hp continuously. An EP running at 15hp requires a 17hp ICE to turn the alternator to deliver 15hp to the drive train.

Fuel burn is a loading issue, you'll burn more using ICE to power EP.

What is your argument?
If by continuously you mean for 30 minutes every 8 hours, then sure. Continuously. I guess words don't matter anymore. Please read the manual.

You'll be using so much fuel that you won't notice your engine melting anyway. Check the fuel consumption for that engine at that HP/RPM. Good luck.
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Old 11-12-2018, 20:05   #1539
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Re: Oceanvolt Hybrid Motor

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Originally Posted by ssmoot View Post
I only care about HP inasmuch as I need a particular number to meet my cruising goals. From there it's totally unimportant.

The 1/2 rated output comes not because EP horsepower is "worth more" than diesel horsepower (whatever that's supposed to mean other than derating a bit for duty-cycle). It comes from the idea that a fuel efficient generator will provide the energy I need much more efficiently than a Diesel engine connected to the props rated similarly.

Because the diesel engine's rating is peak power where its very inefficient, while the generator should be producing it's rated power at its most fuel efficient.

I don't know how many more ways that can be said.

Either you understand that, but don't agree with sizing your power requirements like that. Which is totally your prerogative and doesn't make you wrong. Don't take it so personally! Powerboats aren't for me. That doesn't make them "wrong".

Or you're having trouble understanding it, but would agree with the premise. Or you don't understand it and I can't make you understand it. If that's the case, I'm sorry, but I don't think I have the vocabulary to help you out. It's me, not you.




"faithful". Comes off a bit whinging don't you think?



I'm pretty sure I've seen no one say that. I mean, the engines I used as an example earlier have almost 1L between them. Unless your goal is producing the most horsepower per liter I think you're a bit lost.



No, that's obviously not the case. You could size up your generator, and still be more efficient, but I wouldn't. 50% seems about right to me. If I can run at WOT for a few hours I think that's a good benchmark. From there I'd be happy to run continuously, and fuel efficiently, while backing off a couple knots.



So I can choose to believe you've got some serious reading comprehension problems, or I can just accept you're just ungodly stubborn and no amount of explanation will ever satisfy you and I'm wasting my time.

I'm going to go with stubborn. You built your own boat after all right? That's pretty impressive. It's served you well. But I think I'd rather hash this one out with a brick wall at this point.
Once you start with the personal **** you've lost the argument.
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Old 11-12-2018, 20:14   #1540
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Re: Oceanvolt Hybrid Motor

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If I may offer a suggestion, it may help the conversation here to have a set of working assumptions that you copy and paste into each post so everyone understands the context the comments are made within.

Then the focus can be on the actual discussion and not a lot of clarifying and back forth.

Maybe even state, roughly, a couple of real systems to compare or use as a starting point?
Later on this evening I'll have some time to put together a basic use case, which the more learned people can add to, and that might help this thread stay on track and get everyone talking a common language?

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I'm sure there will be breakthroughs, but will we live to see them? I'm not sure.
Hi Dockhead, thanks for contributing. We're probably not as far away as some might think. There's lots of factors at play but growth at the beginning is always slow. If I may, I sent you a PM about a missing post, could you please spend a quick minute to reply? Thank you.
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Old 11-12-2018, 21:14   #1541
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Re: Oceanvolt Hybrid Motor

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Originally Posted by bridaus View Post
No you cannot, the engines will die during warranty, but they will not be fixed under warranty.
Sorry, but you can run at more than 50% of the HP rating and they will still cover it under warranty...of course, it's extremely unlike to need any warranty work anyway.

Others have posted and quoted....continuous duty is usually around 80% of peak HP...unless the engine has been derated, in which case it's even higher.

I know this is discussion is geared more towards diesels but your average bass boat use is either at idle or the throttle is fire walled. Never heard of anyone having warranty claims (or denied warranty claims) because they ran at full throttle most of the time.
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Old 11-12-2018, 21:44   #1542
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Re: Oceanvolt Hybrid Motor

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Originally Posted by valhalla360 View Post
Sorry, but you can run at more than 50% of the HP rating and they will still cover it under warranty...of course, it's extremely unlike to need any warranty work anyway.

Others have posted and quoted....continuous duty is usually around 80% of peak HP...unless the engine has been derated, in which case it's even higher.

I know this is discussion is geared more towards diesels but your average bass boat use is either at idle or the throttle is fire walled. Never heard of anyone having warranty claims (or denied warranty claims) because they ran at full throttle most of the time.
Come on. Do you seriously think you know more about your engines than someone who.... um doesn't actually know what engines you have?
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Old 11-12-2018, 22:14   #1543
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Re: Oceanvolt Hybrid Motor

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Originally Posted by 44'cruisingcat View Post
Come on. Do you seriously think you know more about your engines than someone who.... um doesn't actually know what engines you have?
I had a diesel that said this in the manual:
"Volvo Penta recommends a cruising speed in the range 500–1000 rpm lower than maximum rpm at WOT."
Then the warranty book (with the 5 year warranty terms) refers to that manual.
The only gotcha was that I had to use it for leisure and not for commercial use.
I always bring flip-flops and beer, so leisure=yes.
It seems funny to me that someone in this thread thinks that such treatment would make the engine "die under warranty".
Weird.
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Old 11-12-2018, 23:00   #1544
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Re: Oceanvolt Hybrid Motor

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Originally Posted by cyan View Post
I had a diesel that said this in the manual:
"Volvo Penta recommends a cruising speed in the range 500–1000 rpm lower than maximum rpm at WOT."
Yeah, but what would they know?
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Old 12-12-2018, 01:14   #1545
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Re: Oceanvolt Hybrid Motor

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Originally Posted by transmitterdan View Post
Ok, let's stipulate a 20HP continuously rated ICE running at 15kW continuously. It will last thousands of hours. And where do you get the "massive quantities of fuel" by running at continuous rated HP? It should be near max fuel efficiency should it not?

Max efficiency for most diesels is about 70% to 80% of rated power. This assumes -- and this is important -- that the engine is operating at the best RPM and throttle condition for the given power output. At max rated power efficiency will be down by about 10%, but this also depends very much on the particular engine -- some of them can overfuel at high load and RPM and then fuel consumption goes up a lot more than that.


But assuming you don't push the engine into an overfueling condition, the hit is about 10%, about the same you get from running the engine at 40% or so of it's rated power.


To run a sailboat in real life conditions you need varying power output. A tiny bit of headwind or sea can easily require double the horsepower for the same speed which might be a required in a dead calm and flat sea. A bit of tailwind, or for God's sake, motorsailing, can require a bunch less.



Therefore, chasing this 75% sweet spot is not a real life thing. In reality, whatever type of drive you have, you will be using the engine above and below the sweet spot most of the time.
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