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Old 23-08-2018, 11:30   #1306
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Re: Oceanvolt Hybrid Motor

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Originally Posted by ssmoot View Post
I agree.

Except "44hp" is purely marketing if you don't actually use it. Hooning about aside, how often, for how long, are cruisers, out of necessity, running their boats at redline?

Because that's the only time you've got a "44hp" engine.

When taking the lumpy torque curves into account, it's my suspicion that most cruisers would be served perfectly fine by an EP system rated for a much lower peak output as it would have a much more usable powerband.

My 125kw EV (Chevy Bolt) is almost as fast....
The automotive comparison doesn't hold up when talking about sail boats.

As you indicated, car HP is driven not by cruising speed power need but by acceleration from a stop. In city driving where you go from 0 to 40mph and back to 0 evey 30-60 seconds, brisk acceleration is a nice performance feature and the instant torque from zero rpm allows you to spec a lower peak HP electric motor and get similar performance to an ICE

A cruising boat that comparison quickly breaks down.
- Your average cruising boat under power gets up to 5-8kts cruising speed....and it stays there often for hours. Assuming they didn't muck things up in design, the engines will be running at or near their ideal output at those speeds so the torque advantages go away.
- Starting and stopping unlike a car where there is a direct correlation between power and acceleration giving the EV an advantage off the line...on a boat, the prop will initially slip thru the water allowing the engine to quickly spin up to higher RPM where it produces more power before the prop really hooks up and starts pulling...but acceleration really isn't a big priority in displacement boat engine sizing in the first place. When you see someone firewall the throttle docking with a cruising boat...it's usually already gone to poo.

Now I will give you credit that most of the time a 44hp engine is not putting out 44hp but it would be odd to spec an engine that runs at only 25% of it's rated output. Typically, I would expect something more on the order of 50-75% at normal cruising speed. Of course, when conditions get bad, what happens...
- You can take the tractor approach (fairly typical for EV boats), they put on a big low pitch prop. Like a tractor it will keep the boat moving against adverse conditions but slowly. The down side is when conditions are more modest and you would like to get up near hull speed...it isn't possible. You can do the same thing with a smaller diesel and reduction gears to turn the bigger prop. This is a running gear issue that has nothing to do with what is turning the prop shaft.
- If you leave the prop standard, there isn't enough power with the EV to maintain the same speeds in normal conditions and you lose speed in adverse conditions.
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Old 23-08-2018, 11:34   #1307
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Re: Oceanvolt Hybrid Motor

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I agree, 11HP does not equal 44HP and I can't read anywhere in #1283 that suggested the Lipari was at full power.... But I think some are missing the point. Surely the purpose of a propulsion system is to assist your sailing? If the OV system could push my boat away from a danger in a 40knot headwind and rough seastate I'd be happy. Me being me I'd try to avoid such weather in the first place or if I was a better sailor then maybe I'd just pick an alternative safe line of sailing that missed the danger ahead of time. I'm sure the OV is not all things to all people but for JaJapami & many (me included) it would be fine as our style of sailing suits it. This is exactly why some of us here love cruising cats, others wouldn't touch them with a barge pole... These choices are ours. I am personally very grateful for this thread and JaJapami's input as it gives us knowledge for personal consideration.
As has been stated multiple times...if all you need is power to get in and out of harbor and will sail the rest of the time, EV is very much viable now...

The vast majority of cruisers are not that purist about sailing and if you are that purist, the fuel savings are negligible anyway...so it becomes down to some sort of moral imperative that you are following.
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Old 23-08-2018, 11:36   #1308
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Re: Oceanvolt Hybrid Motor

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Originally Posted by BigBeakie View Post
Well perhaps I have misread JaJapami's comments on this in post#1283 and a previous post.

As I understand it he in his FP Saba 50 with OV SD15kW (22 HP) was in company with a FP Lipari 40 that had 40HP diesels motoring against a 28-32 Knot headwind with 1.5 to 3 meter seas and they were doing about same SOG at about 3 knots.

His motor controllers were only allowing about half power to be used in his 15kW motors and he had alot of hull growth.

Perhaps the Lipari engines were just ticking over? But, I doubt it.
Actually quite likely. Bashing into short steep waves at high speed is uncomfortable and hard on the boat. Backing off will often make the ride more comfortable and ease the stress on the boat.
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Old 23-08-2018, 12:55   #1309
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Re: Oceanvolt Hybrid Motor

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I seldom run my 50HP Yanmar at top RPM. Most of the time I get by at not much more than a fast idle, since I'm trying to stay efficiently below hull-speed for maximum range.
I'm guessing a Yanmar 4JH5E?

So on that engine there's a small knee in fuel consumption around 1750 RPM. Maximum torque is actually around 1600 RPM. Yanmar's specs don't show SAE units so 155Nm is about 114lbft. At 1750 RPM that's 38hp.

Which is a lot more than I expected looking at other Yanmar and Volvo Penta engine's torque curves. Your engine seems to have especially robust low end output.

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None of which proves that an electric HP = 3x diesel HP. But that is what some people have been claiming.
I think it's fairer to say that many people aren't interested in inefficiently running at redline. And that if what they really want is a 38hp engine with maybe some extra breathing room 99% of the time, then a straight swap from a 4JH5E to a 38kW motor would be ridiculously overpowered and not really comparable considering you'd have significantly more power everywhere in the rev range except where they meet at redline.

Put another way, saying that only a 38KW motor can replace a 50hp engine is the same thing as saying "only redline performance factors into my engine sizing decisions". Which, if that's the case, that's totally up to you. But I get the impression that how people actually end up using their engines is at odds with that.

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Locomotives need zero-RPM torque, and that's one reason they use electric motors. Boats don't need that torque characteristic.
I'm no train engineer. I don't doubt that's a good point. But I suspect running the generators at their most fuel efficient RPM is the primary reason. But my theory may not hold water.
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Old 23-08-2018, 14:03   #1310
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Re: Oceanvolt Hybrid Motor

Trains use electric motors because of high torque at low RPM without the need for a mechanical transmission. The generators have load bank resistors for wasting power to keep the genset engines happy at low speeds and for electronic braking. Trains spend 95% of their life at cruising speed and that’s where they are most efficient. But they can’t get up to cruise speed with any realizable mechanical transmission.

We have heard some details here about EP systems in the field. The issues vary from predictable to surprising. The controllers overheat. The big blade, slow turning props create high structural stresses during heavy wave action. The electric motors run really hot (>100C). All of that is by design so they can get lowest cost, max efficiency and low weight. Over time we will hopefully learn if there are other unforeseen design trade offs that arise.

Meanwhile, 99% of sailors run their engines at 80% of max HP when cruising under auxiliary and are operating the engine cool (80C) and comfortable with a small prop that doesn’t get ripped off the strut by a big wave. And they are the ones too stupid to see the advantages of EP. Most cruisers are seeking a destination, not happy to be sailing no matter the weather. They want to get where they are going comfortably and efficiently. In many cruising grounds there is way more motoring than sailing.
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Old 23-08-2018, 14:46   #1311
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Re: Oceanvolt Hybrid Motor

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Originally Posted by valhalla360 View Post
The automotive comparison doesn't hold up when talking about sail boats.
Then diesel electric shipping? That's not considered new or experimental at this point right?

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Originally Posted by valhalla360 View Post
the instant torque from zero rpm allows you to spec a lower peak HP electric motor and get similar performance to an ICE
The instant torque definitely helps the "peppy" factor, but EVs are actually torque-limited at low speed for drivability. So I think it's fair to say the torque curve more important than the 0RPM delivery.


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- Your average cruising boat under power gets up to 5-8kts cruising speed....and it stays there often for hours. Assuming they didn't muck things up in design, the engines will be running at or near their ideal output at those speeds so the torque advantages go away.
This is exactly my argument. That people don't (or probably shouldn't be, however you want to slice it) sizing their diesel propulsion based on the ridiculously thirsty redline horsepower. They should be sizing it for cruising RPMs.

Fuel consumption on a 4JH5E when actually producing 50hp is near enough 3gal/hr. If you're pushing both engines you'll run out of fuel on a Helia in 20 hours. You'll also be pretty far outside it's continuous use ratings for that RPM IIRC, but that's another conversation maybe.

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Typically, I would expect something more on the order of 50-75% at normal cruising speed.
Seems closer to 50% typically (the Yanmar 4JH5E is a monster, but the 4JH45 where the most efficient RPM, around 1600, gets you about 20hp), but right. That's all I've been trying to say. IMO, when trying to compare these particular apples and oranges, using a peak hp rating is not incredibly relevant.
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Old 23-08-2018, 15:24   #1312
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Re: Oceanvolt Hybrid Motor

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We have heard some details here about EP systems in the field. The issues vary from predictable to surprising. The controllers overheat. The big blade, slow turning props create high structural stresses during heavy wave action. The electric motors run really hot (>100C). All of that is by design so they can get lowest cost, max efficiency and low weight. Over time we will hopefully learn if there are other unforeseen design trade offs that arise.

Meanwhile, 99% of sailors run their engines at 80% of max HP when cruising under auxiliary and are operating the engine cool (80C) and comfortable with a small prop that doesn’t get ripped off the strut by a big wave. And they are the ones too stupid to see the advantages of EP. Most cruisers are seeking a destination, not happy to be sailing no matter the weather. They want to get where they are going comfortably and efficiently. In many cruising grounds there is way more motoring than sailing.
I don't think anyone's stupid for choosing diesel. At least I hope not. I'm probably going with diesel on my own boat.

As you've pointed out, Oceanvolt is building a, being generous, mixed reputation for reliability. I personally don't understand why Torqueedo gears have to sound like they're eating themselves. There aren't a ton of "off the shelf" options in this tiny market that look really compelling. They're expensive for what they are, the engineering seems unproven.

What I personally have an issue with is letting that characterize EP as a whole. It's a proven tech, applicable to boats, with a lot of benefits. Intermediate, low hours usage? Perfect! High torque? Ideal. The trades in weight mean you get a lithium house bank that's anywhere from 3X to 8X as big as most? Who wouldn't want to only have to charge a tenth as often? You might even produce power under sail? Can't hate on that. Instead of two diesels and a generator, you could go with one large generator for your house/propulsion bank, or two smaller ones, and get right of a generator? Sounds great right? Low/No maintenance? You betcha!

So what's the catch? Right now, if you want a supported, out-of-the-box solution, they're a bit pricey. And the reputation of the companies selling these systems is an open question.

Though going back to price, I don't think it's as far apart as might be assumed. I've had a real hard time finding online pricing for generators and diesels personally, but it seems like a pair of "big" Yanmars and a ~10kW Onan generator might easily hit over $50,000, and that doesn't include your house bank. That's not exactly pocket change.

But reality is most builders don't seem real open to the idea. And they're getting a deep discount on the Diesel engines. So even if yes, environmental concerns are a personal priority, it's not a slam dunk decision.

Personally I hope that changes in the next 5 years or so.
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Old 23-08-2018, 17:18   #1313
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Re: Oceanvolt Hybrid Motor

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Originally Posted by ssmoot View Post
I'm guessing a Yanmar 4JH5E?

So on that engine there's a small knee in fuel consumption around 1750 RPM. Maximum torque is actually around 1600 RPM. Yanmar's specs don't show SAE units so 155Nm is about 114lbft. At 1750 RPM that's 38hp.

Which is a lot more than I expected looking at other Yanmar and Volvo Penta engine's torque curves. Your engine seems to have especially robust low end output.
I actually overstated the HP, it's more like 38 HP. I have a Yanmar 4H3E, naturally aspirated. The torque curve shows a peak at 2000 RPM, which probably doesn't change your observations very much.

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Originally Posted by ssmoot View Post
I think it's fairer to say that many people aren't interested in inefficiently running at redline. And that if what they really want is a 38hp engine with maybe some extra breathing room 99% of the time, then a straight swap from a 4JH5E to a 38kW motor would be ridiculously overpowered and not really comparable considering you'd have significantly more power everywhere in the rev range except where they meet at redline.

Put another way, saying that only a 38KW motor can replace a 50hp engine is the same thing as saying "only redline performance factors into my engine sizing decisions". Which, if that's the case, that's totally up to you. But I get the impression that how people actually end up using their engines is at odds with that.
Bur deciding where that redline should be is kind of the point. If you want it, you need to design for it even if you seldom operate there.

I'm pretty happy with my engine. I run it at low power for long periods when transiting the wastelands of a dead-air high-pressure system, and occasionally around 3000 RPM when I need to make it through a pass before the current turns. Engine redline is 3800. I think I've briefly taken it to 3500 just to see what happens.

Everyone should take a look at the propeller power curves (my Yanmar spec has them). They show the power a correctly-designed prop uses at varying RPMs, and how that matches up with the engine output at redline. As the RPM drops the diesel can deliver much more power than the propeller can accept. Looking at electric motor power curves, the mismatch seems pretty similar.

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I'm no train engineer. I don't doubt that's a good point. But I suspect running the generators at their most fuel efficient RPM is the primary reason. But my theory may not hold water.
Transmitterdan described what I've heard elsewhere about locomotive engines. The big advantage is eliminating the fancy gearing that would be needed to get the train rolling from a dead-stop. Electric motors are perfect for that application
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Old 23-08-2018, 23:34   #1314
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Re: Oceanvolt Hybrid Motor

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Please don't mistake my insistence on being realistic as an attack on the concept of electric drive. I am quite impressed by the efficiency improvements and power density of modern electric propulsion system components. I just don't think that magical thinking helps in the long run. It leaves people disappointed (the early Lagoon electric systems) and doesn't help advance the technology. I wish that battery technology were even close to being on parity with diesel fuel when it comes to energy density, but it isn't, and I see nothing game-changing on the horizon. Even if solar panels were to somehow become 100% efficient, most boats (like mine) would not be able to carry enough to cover my electric propulsion needs (or to be honest, my desires).

Other people, other boats, may find these necessary compromises (or reductions in available power) to be entirely appropriate for their needs. I will continue to follow their progress with great interest.
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Old 23-08-2018, 23:54   #1315
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Re: Oceanvolt Hybrid Motor

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I agree.

Except "44hp" is purely marketing if you don't actually use it. Hooning about aside, how often, for how long, are cruisers, out of necessity, running their boats at redline?

Because that's the only time you've got a "44hp" engine.

When taking the lumpy torque curves into account, it's my suspicion that most cruisers would be served perfectly fine by an EP system rated for a much lower peak output as it would have a much more usable powerband.

My 125kw EV (Chevy Bolt) is almost as fast (0.7s slower 0-60) as my previous gas/turbo vehicle (Volvo S90 T6) with twice the horsepower off the line. It also has a lot more usable power as it never has to worry about suboptimal shifts, warm or cold starts, turbo lag, etc.

The price you pay is that it's geared to give you all that power up until it's "redline" at 90mph. So you're not gonna be blazing down the Autobahn at 150mph.

The gas engine needs 316hp not because it needs 316hp, but because it spends the vast majority of it's life outside of it's powerband and you can't increase the low-end without increasing the top-end number. Between 2,000 to 4,000 RPM it's actually an 80hp to 200hp motor.

Which then explains how the EV can be so competitive. Within the range they're actually used, the vehicles (~3,600lbs and ~4,100lbs respectively) have very similar power to weight ratios.

Ah, but the EV doesn't have the peak, top-speed performance of the ICE vehicle.

That's true. But on a boat we're talking about a ~20% difference in top speed perhaps? And again, for how often and for how long?

As a former motorcyclist, I can't count the number of times someone tried to tell me "power" saves and was able to get them out of a squirrely situation. On the road at least, the only power that factors into safety is the power of your brakes/tires. You can try to use a contrived example to demonstrate hp saves, but guaranteed that same hp also encouraged you to put yourself into more dangerous situations as well. There's a reason insurance adjusters don't give you a discount for opting for the bigger engine.

So, I have very little on-water experience. When I hear that you need that (peak only!) horsepower to run from weather or something, it may be unfair, but I mentally put that into the same category as the 20yo sport-bike rider telling me that what saved him from that truck about to t-bone him was the 150hp between his knees. When it's much more likely defensive driving, brakes and a well maintained bike would come out on top 99% of the time.

tl;dr: "hp" is a marketing number that only refers to peak performance, and I feel like there's an over reliance on it in these conversations. Guaranteed your new 45hp Yanmar has much more usable power with a flatter torque curve, better response, better power-to-weight ratio, reliability, (MTBF, not some story about how bullet-proof the block may be) long etc than some 50 year old engine with the same peak rating as well, but to read these conversations you'd think the only thing that mattered was a peak rating that's (I suspect) almost never used, even in the worse conditions. Because who thinks a bad storm is a great time to test running at redline for hours? But that's just me speculatin'.

If I'm totally off base with how you guys are actually using your engines in the water, I'd love to be set straight. I'm sure I could learn a lot from your experiences.
"Because that's the only time you've got a "44hp" engine."

Actually you almost never have a 44hp engine. The best an engine will be is between 250-750 hrs, before 250 engines are not run in and are not at peak and after 750 engines leak hp through wear and tear..
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Old 24-08-2018, 04:14   #1316
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Re: Oceanvolt Hybrid Motor

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"Because that's the only time you've got a "44hp" engine."

Actually you almost never have a 44hp engine. The best an engine will be is between 250-750 hrs, before 250 engines are not run in and are not at peak and after 750 engines leak hp through wear and tear..
Assuming this is true (which I doubt) how does EP change the situation?

If the HP changed significantly with such few hours it would be observable in fuel consumption and in other ways. I have noticed no change in performance or efficiency and we have nearly 2K hours on our engine. I think your observation might be valid in the previous century but not so much today.
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Old 24-08-2018, 04:24   #1317
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Re: Oceanvolt Hybrid Motor

Ssmoot is right to say that in a bad situation it's a bad idea to redline the engine. No one is suggesting that is a good strategy. The issue is that we are being told that by switching to EP we can get same performance with 1/2 the HP ICE engine, save fuel and when prop technology is perfected we can recharge batteries under sail with no loss in boat speed. It's all going to be so wonderful to never have to fill our diesel tank on a RTW cruise. Someday soon we are going to run our air conditioning 24/7 with all the extra energy we will have for free. I exaggerate slightly but not all that much.
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Old 24-08-2018, 06:01   #1318
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Re: Oceanvolt Hybrid Motor

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Then diesel electric shipping? That's not considered new or experimental at this point right?

Certainly not but it's used for a different reason that doesn't apply to small cruising boats. Similar to diesel-electric trains, it's all about acting as a transmission because a mechanical one can't handle the power. On ships, it's usually cruise ships and other specialty ships because they need/want additional maneuverability under their own power. Your bog standard base freighter is generally direct drive because it's more efficient.

The instant torque definitely helps the "peppy" factor, but EVs are actually torque-limited at low speed for drivability. So I think it's fair to say the torque curve more important than the 0RPM delivery.

Taken to the extreme sure...no one needs a 4sec 0-60 time to feel peppy. If you look at a more realistic design like the leaf or the bolt, they are sizing the engine based more on needs compared to tesla spec-ing based on marketing. Plus torque limiting isn't limited to EVs. A lot of your diesel pickups are torque limited because they can twist the axles apart if you stomp on it.

This is exactly my argument. That people don't (or probably shouldn't be, however you want to slice it) sizing their diesel propulsion based on the ridiculously thirsty redline horsepower. They should be sizing it for cruising RPMs.

Again, if you want to replace a 44hp with a 40hp...I might buy that idea but people claiming you can replace it with 11hp are not doing an apples to apples comparison of power plants. If you are sizing it so 70% of peak gives you a nice 80-90% of hull speed, that gives you a bit extra to handle tough conditions.

Fuel consumption on a 4JH5E when actually producing 50hp is near enough 3gal/hr. If you're pushing both engines you'll run out of fuel on a Helia in 20 hours. You'll also be pretty far outside it's continuous use ratings for that RPM IIRC, but that's another conversation maybe.

And most of the electric systems people are talking about can't run flat out for an hour even with the much lower peak power ratings...certainly nothing close to 20hr. While it's outside the ratings, in an emergency, I'm willing to sacrifice some longevity as that is what those ratings are really about (it doesn't mean they will fail if you run at peak output for 10min more than the rating)

Seems closer to 50% typically (the Yanmar 4JH5E is a monster, but the 4JH45 where the most efficient RPM, around 1600, gets you about 20hp), but right. That's all I've been trying to say. IMO, when trying to compare these particular apples and oranges, using a peak hp rating is not incredibly relevant.
Even if we assume your 20hp is right (I think you are estimating low), that's still way more than 11hp or even kw which is the peak output with nothing left in reserve.

edit: I realize I mixed HP and KW in a few places but the points still stand that electric motors a small fraction the size of diesel are not equivalent.
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Old 24-08-2018, 07:48   #1319
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Re: Oceanvolt Hybrid Motor

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Assuming this is true (which I doubt) how does EP change the situation?
The motor doesn't suffer from compression losses or significant friction losses as it ages (up until you need new bearings I suppose).

But I agree-ish. An old Perkins engine? I seriously doubt that's making rated horsepower. A modern Yanmar? I'd be surprised if its output varies much at all over it's serviceable lifetime. Modern Diesel trucks certainly don't have that issue AFAIK.
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Old 24-08-2018, 08:16   #1320
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Re: Oceanvolt Hybrid Motor

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I exaggerate slightly but not all that much.
Maybe. I don't feel like I've seen those comments. But I'm not sure what they have to do with EP in general.

Regarding the 1/2 the power argument though: I think you're talking past whoever you're arguing with. You're looking at peak. They're looking at cruising.

Look at it this way: If Yanmar slapped a 15kW generator onto a 4JH5E tomorrow, letting you get rid of your diesel generator, but limited you to 1800 RPM and forced you to buy a 30kWh battery pack, would you do it for a 20% price premium? They also use that generator to drive the boat off the battery for as long as it lasts, so you'll likely never need to fire up the engines to dock. Only for extended motoring.

It's the same "50hp" engine, but now it's rev-limited to a range where it can only produce something like 38hp max. Maybe they even allow you to over-rev it for a few minutes at a time until a thermostat limits you.

Performance up to the new "redline" is identical. The system overall is more efficient. You get a massive housebank as a nice side-effect. You don't have a dedicated generator anymore so you've got more stowage on your boat and one less engine to maintain.

Would you buy that? Maybe not, but I think a lot of people might?

Ignoring "how you get there", that set of trade-offs looks pretty nice to me. That's basically the EP solution.

So that's a ~28kW engine though. What if, instead, they offered a 20hp engine with the same setup. And when you pushed the needle, you had access to the combined 30kW the engine and motor offered together, but up to the ~1 hour your battery would take it. Now you have even more efficient cruising for a given RPM, lighter weight, and you're only 20% off the maximum output of the bigger 4JH5E, which might result in a half-knot difference in maximum boat speed when motoring.

Would you pay an extra 20% for that house-bank, getting rid of the dedicated generator, silent docking, if it meant your peak output was limited to 1 hour and it cost you a half knot in boat speed?

I think I would.

You can definitely come up with an EP solution that meets that criteria. But I'd also agree that Oceanvolt and Torqueedo probably don't offer it. Torqeedo seems much closer in spec, but their proposed EP system is not anywhere close to only 20% higher cost I'd bet.
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