Oceanvolt Hybrid Motor

[DotDun]

Originally Posted by BigBeakie

So you weren't clawing off a lee shore to avoid disaster, you were choosing to claw towards a destination windward shore? It takes about 12 hours of sustained 40 knot winds to develop breaking 4 meter waves, and that is in only 20 meters of water. That's a very long lived thunderstorm you experienced....

And you held station by running your engines, which is a fair choice, because you did not know how long the adverse conditions would last. Another choice would be to sail, but if your cat is not set up for heavy weather sailing, then the iron genny is your only answer; or heaving to, or turning around and running or deploying a parachute anchor might be alternative answers.

What wind speed would you say your boat would NOT be able to hold station? It sounds like it was maybe about 50 knots, because it was difficult to point?
So, what would you do if you got 60 knots on the nose? Would you run full power into it and just try to keep pointing into it while drifting backwards for as long as you had fuel?

Never been in 60kts of wind other than at anchor. The boat just experienced 140kts of wind at the dock (hurricane), but I wasn't here to see it, came through without a scratch. The main issue with this story was the very steep waves, it happens a lot in the Gulf of Mexico. It would have been way uncomfortable trying to sail into those. Climbing the waves is what impeded forward progress.

I've sailed several times in 35kts sustained gusting 40kts of offshore wind paralleling the coast ~5nm out, waves 2-3m, triple reefed, fairly comfortable.

Originally Posted by BigBeakie

A reasonable amount of battery (cost + multihull weight factor) for EP is, IMO, about an hour of full power. If anyone is contemplating EP, they should realise this, and perhaps ensure they have a boat that is suitably rigged and equipped for heavy weather sailing, because you just never know. Going to sea in a boat that MUST rely on engines or motors to deal with heavy weather is a choice, but IMO, a bad choice, regardless of the auxillary propulsion technology.

It depends whether it's open ocean or near shore. Lot's more options when you're more 50nm from running aground.

So you are going to have 36kwH of battery for your (2) 15kw OV ?? That's (32) 400AH Lithiums (~$16k US).

[txg]

Originally Posted by DotDun

Some will blow off the .1% of the time and state, ‘it’s a sailboat, I’ll have a storm sail’. That tells me they have never been in 40-50kt winds with 4-5m breaking waves trying to claw away from a lee shore. That won’t happen without at least 30kw of drive power and the requisite 32+kw of genset. Forget about the batteries for this task, you won’t be able to afford or carry enough.

Add it all up and it doesn’t make sense anymore.

It's a sailboat, so use your storm sail
I know from personal experience that our old but seaworthy plastic classic can "easily" go to windward in 50-55 kts with storm jib only. "Easily" in this context means it works fine, but it is obviously not an enjoyable ride.

Seriously, the boat you are sailing is simply not designed for acceptable windward performance. It needs your big engines for going upwind. That's fine and there are many usecases where this makes sense.

But please don't blame hybrid or electric drives for not being able to drive your special boat.

[DotDun]

Originally Posted by txg

It's a sailboat, so use your storm sail
I know from personal experience that our old but seaworthy plastic classic can "easily" go to windward in 50-55 kts with storm jib only. "Easily" in this context means it works fine, but it is obviously not an enjoyable ride.

Seriously, the boat you are sailing is simply not designed for acceptable windward performance. It needs your big engines for going upwind. That's fine and there are many usecases where this makes sense.

But please don't blame hybrid or electric drives for not being able to drive your special boat.

Hmm, I never blamed anything, you must be blinded by your sailing bravado. I'll bet you never been on a cat..?

All I'm stating is it takes more power to motor into storm conditions than benign conditions. Hence, if you equip your boat for motoring in benign conditions only, you may not be able to motor during storm conditions. Yep, sailing is always an option, even on my boat.

[BigBeakie]

Originally Posted by DotDun

Never been in 60kts of wind other than at anchor. The boat just experienced 140kts of wind at the dock (hurricane), but I wasn't here to see it, came through without a scratch. The main issue with this story was the very steep waves, it happens a lot in the Gulf of Mexico. It would have been way uncomfortable trying to sail into those. Climbing the waves is what impeded forward progress.

I've sailed several times in 35kts sustained gusting 40kts of offshore wind paralleling the coast ~5nm out, waves 2-3m, triple reefed, fairly comfortable.



It depends whether it's open ocean or near shore. Lot's more options when you're more 50nm from running aground.

So you are going to have 36kwH of battery for your (2) 15kw OV ?? That's (32) 400AH Lithiums (~$16k US).

Jeez, DD, having your boat unscathed coming thru a hurricane at dock, is good going. It's the other boats breaking loose that worries me.

No, we've cut back on the LFP's from the original plan to 24kW because of the amount of regen and how that changes the equation.That's 14 Valence batts at 18kg each, so 252kg for the batts. LFP like to be worked, so we'll be running them down to 20%-30% then charge back up via solar, regen or genset, whichever is best at the time, in whatever combination.

We'll carry quite a bit less diesel for our 16kW DC genset than the Beta 50's would have needed, so we are saving weight big time eliminating the Beta 50's and several hundred liters of diesel.

If it is really cloudy/rainy and we need to motor in no wind situation for many hours, or at least beyond the 6 hours the batts would give, then the DC genset comes on automatically at 20 %DOD gives us full charge in just over an hour, then continue motoring on batts alone for another 6 hours and repeat as necessary. No need for small genset at all.

I so not believe you need a smaller genset at all with this system. We considered it, but the Oceanvolt regen is a game changer.

[DotDun]

Originally Posted by BigBeakie

Jeez, DD, having your boat unscathed coming thru a hurricane at dock, is good going. It's the other boats breaking loose that worries me.

It's all about the preparation!

Originally Posted by BigBeakie

No, we've cut back on the LFP's from the original plan to 24kW because of the amount of regen and how that changes the equation.That's 14 Valence batts at 18kg each, so 252kg for the batts. LFP like to be worked, so we'll be running them down to 20%-30% then charge back up via solar, regen or genset, whichever is best at the time, in whatever combination.

So you won't have your prescribed 1 hour @ full power on batteries alone. You'll have 1 hour at 2/3 power and require the genset running at the same time to fight anything worse than benign conditions. Regen doesn't work while you are motoring so it doesn't make any sense why regen would encourage a smaller battery bank.

Originally Posted by BigBeakie

We'll carry quite a bit less diesel for our 16kW DC genset than the Beta 50's would have needed, so we are saving weight big time eliminating the Beta 50's and several hundred liters of diesel.

If it is really cloudy/rainy and we need to motor in no wind situation for many hours, or at least beyond the 6 hours the batts would give, then the DC genset comes on automatically at 20 %DOD gives us full charge in just over an hour, then continue motoring on batts alone for another 6 hours and repeat as necessary. No need for small genset at all.

I so not believe you need a smaller genset at all with this system. We considered it, but the Oceanvolt regen is a game changer.

Refresh the numbers for me. How does 24kW of batteries allow for 6 hours of motoring? At what speed?

It appears that with a full battery charge and genset running, you'll be able to motor at full power for 1 hour, then you'll have no more than 1/2 power until you run out of diesel. Your batteries won't charge while motoring at 1/2 power (15kW) as all the genset output is going to the motors.

Didn't you provide regen numbers of ~1kW @ 8kts and ~2kW @ 10kts? So 10+ hours sailing @ 10kts will charge your batteries?

[BigBeakie]

Originally Posted by DotDun

It's all about the preparation!



So you won't have your prescribed 1 hour @ full power on batteries alone. You'll have 1 hour at 2/3 power and require the genset running at the same time to fight anything worse than benign conditions. Regen doesn't work while you are motoring so it doesn't make any sense why regen would encourage a smaller battery bank.

You never really want to use full power. Why? Because the benefit is so small that it makes no sense due to the resistance-power curve. For example for our boat we'll get about 7.5 knots at full power, and you are correct, we'd be able to motor for about 45 minutes at full power, using 30kW from the batteries.
BUT, at half power consumption, i.e. using 15kW, we will motor at 6.5 knots for a little over an hour and a half. Is it usually worth it to lighten up on the throttle? Depends on the situation, obviously.

And don't take the "hour of power" literally DD, it is a rule of thumb for sizing EP systems, it is about right for a cruising cat, other than a condomaran. I have not done the figures for the bathtubs, but they have significantly more water resistance due to LwL/Bh low ratios. Our boat is 12:1, some charter designs are 8:1 or worse.



Refresh the numbers for me. How does 24kW of batteries allow for 6 hours of motoring? At what speed?

When becalmed, we'll motor at about 4.5 to 5 knots using 4kW from the batteries. We have just over 3 kW of solar, and we could run the motors directly from the solar alone, no battery power used at all, if we needed to. Which is unlikely. But if we had a complete electrical system failure from lightning or something???, we could keep going, albeit slowly.

It appears that with a full battery charge and genset running, you'll be able to motor at full power for 1 hour, then you'll have no more than 1/2 power until you run out of diesel. Your batteries won't charge while motoring at 1/2 power (15kW) as all the genset output is going to the motors.

That's about right, but remember running at half power from the genset is not too shoddy. It's not like we come to a standstill as the EP has an uncanny thrust against resistance.

Didn't you provide regen numbers of ~1kW @ 8kts and ~2kW @ 10kts? So 10+ hours sailing @ 10kts will charge your batteries?

I believe that was the original regen numbers from the SD15 system before the release of the Servoprop recently. With the Servoprop we'll get about 2 kW at 8 knots, and 3kW at 10 kW from EACH motor.

And that is why I don't think a small genset is needed, the Servoprop delivers as much power as a reasonable regular genset, just sailing along.

Making any sense now?

[Mark424]

Originally Posted by Valiente

At this stage it seems to me that with LifePO and Oceanvolt saildrives it all could start to make sense in a 40-45feet cruising catamaran.

My gut aproach is: 1 big Gen in one hull, smaller gen+LifePo bank in the other, with the following usage pattern:
- Slip in/out from Marina under optimal conditions or Help lifting anchor: Electric from lifepo batteries*
- Slip in/out from Marina under less than optimal conditions and economical motorsailing: Electric from small genset+ (LifePo for Peak power)*
- Full Power needed: Marina in/out under hard conditions, or sustained motoring against strong headwinds: electric from both Gensets (+ LifePo for peak power short burst)

I'd tweak your approach.
(1) Diesel Saildrive in one hull w/ serial generator/motor between diesel and saildrive.
(2) (optionally) drop the 2nd generator, and have electric drive in the second hull. Batteries to suit needs, maybe carbon foam instead of LiFePo, (or buy a tesla power wall 2 Much cheaper per KWH.)

For low power/short time period, you can still run electric only w/ both props.

For long distance you'll need a generator running in your scheme, so just use one diesel+saildrive and save the conversion inefficiencies and extra cost. You can generate extra power if you need it w/ the serial gen on the flywheel. A larger main diesel/gen will be much less weight than a small + medium sized one. One set of controls, exhaust, cooling system, etc. Monos have been cruising for ever w/ a single diesel, they are reliable.

For motor sailing, when the batteries are full, shut down the diesel and use the electric on the other hull for the assist.

[valhalla360]

Originally Posted by BigBeakie

I believe that was the original regen numbers from the SD15 system before the release of the Servoprop recently. With the Servoprop we'll get about 2 kW at 8 knots, and 3kW at 10 kW from EACH motor.

And that is why I don't think a small genset is needed, the Servoprop delivers as much power as a reasonable regular genset, just sailing along.
]

Just out of curiosity, this thread has been kicking around for almost a year and a half. How's the construction on your boat coming along?

[DotDun]

Originally Posted by BigBeakie

You never really want to use full power. Why? Because the benefit is so small that it makes no sense due to the resistance-power curve.

You do realize the 'resistance-power' curve you talk about actually uses power. The ability of an electric motor to deliver full power at low rpm also uses full power at low rpm.

Originally Posted by BigBeakie

For example for our boat we'll get about 7.5 knots at full power, and you are correct, we'd be able to motor for about 45 minutes at full power, using 30kW from the batteries.
BUT, at half power consumption, i.e. using 15kW, we will motor at 6.5 knots for a little over an hour and a half. Is it usually worth it to lighten up on the throttle? Depends on the situation, obviously.


When becalmed, we'll motor at about 4.5 to 5 knots using 4kW from the batteries. We have just over 3 kW of solar, and we could run the motors directly from the solar alone, no battery power used at all, if we needed to. Which is unlikely. But if we had a complete electrical system failure from lightning or something???, we could keep going, albeit slowly.


That's about right, but remember running at half power from the genset is not too shoddy. It's not like we come to a standstill as the EP has an uncanny thrust against resistance.

Remember, that uncanny thrust against resistance uses power, whatever is needed up to and including full power.

Originally Posted by BigBeakie

I believe that was the original regen numbers from the SD15 system before the release of the Servoprop recently. With the Servoprop we'll get about 2 kW at 8 knots, and 3kW at 10 kW from EACH motor.

Hypothetical: If your boat sails @ 10kts in 15kts wind, a guess would be it'll take 20+kts of wind to maintain 10kts of speed when making 6kW of regen power.

Originally Posted by BigBeakie

And that is why I don't think a small genset is needed, the Servoprop delivers as much power as a reasonable regular genset, just sailing along.

Making any sense now?

So, here are your expected numbers:

7.5kts = 30kW
6.5kts = 15kW
4-5kts = 4kW

I am suspicious about these numbers. I personally think you'll get more than 7.5kts using 30kW (depends on prop). In turn I think you'll be doing considerably less than 4-5kts at 4kW.

And, a 24kW battery bank won't deliver 6 hours @ 4kW. It'll do at best 4.5 hours (minus loss in efficiency).

Looking forward to your real world testing!

[44'cruisingcat]

Originally Posted by BigBeakie

LFP like to be worked, so we'll be running them down to 20%-30% then charge back up via solar, regen or genset, whichever is best at the time, in whatever combination..

Sounds like you're getting bad advice from someone?

LIFePO4 can be cycled more deeply than lead acid batteries for sure, but "like to be worked"?

No. They don't "like" to be worked. The shallower the cycles, the more cycles they'll last. Deeper cycles, shorter life.

And you seem to be anticipating charging to 100%, which is generally not advised.

[BigBeakie]

Originally Posted by 44'cruisingcat

Sounds like you're getting bad advice from someone?

LIFePO4 can be cycled more deeply than lead acid batteries for sure, but "like to be worked"?

No. They don't "like" to be worked. The shallower the cycles, the more cycles they'll last. Deeper cycles, shorter life.

And you seem to be anticipating charging to 100%, which is generally not advised.

Wow, You are such a pendant. The batteries we are using can be discharged every single day to 80% DoD for 11 years. If that cannot be summarized as "like to be worked" I don't know what does.

Yes, the deeper the discharge, the less cycles you get, in theory... yeah, yeah, but who cares?

By the time 11 years rolls by, battery technology will have improved somewhat I would expect, and then we can re-evaluate a re purchase. So, who cares?

[44'cruisingcat]

Originally Posted by BigBeakie

Wow, You are such a pendant. The batteries we are using can be discharged every single day to 80% DoD for 11 years. If that cannot be summarized as "like to be worked" I don't know what does.

Yes, the deeper the discharge, the less cycles you get, in theory... yeah, yeah, but who cares?

By the time 11 years rolls by, battery technology will have improved somewhat I would expect, and then we can re-evaluate a re purchase. So, who cares?

Yeah I'm a pedant. Maybe if you stopped stating garbage as though it were fact, others wouldn't need to keep pointing it out.

[BigBeakie]

Originally Posted by 44'cruisingcat

Yeah I'm a pedant. Maybe if you stopped stating garbage as though it were fact, others wouldn't need to keep pointing it out.

Really? Are you saying the figures I've stated above for the Valence 24V batteries is wrong? Is it "garbage"? Their data sheet is attached for you to refute. Take your best shot....

How about you share your data that shows that?

Actually, how about you put forth any facts to support your case, that would be refreshing for a change.

[BigBeakie]

The Valence data sheet is too big to attach, but here's the url to it:

https://www.valence.com/products/sta...ttery-modules/

If any of this is "garbage" kindly point it out and supply your data.

[44'cruisingcat]

So where on the data sheet do the batteries state how much they "like to work"?