Viability of electric only propulsion in 2018 - is there a good option after all?

[Dockhead]

Originally Posted by KTP

A 20kWh bank (which is pretty small by electric vehicle standards) could hold the equivalent of 8 liters of diesel. Not much really but I guess it adds up over time. If you did 2000 charge/discharge cycles to 50% that would be 8000 liters of diesel.

So how long will it take to pay for itself, at that rate? If you went out every single weekend, both Saturday and Sunday, so 104 times a year, that would still require 19.2 years to save those 8000 liters of diesel, and I bet the installation costs more than 8000 liters of diesel do.


This will look different when we get better storage. 8 liters of diesel is only 16 miles in my boat -- in really good conditions. If we could store enough for 50 or 60 miles of motoring -- then that's a quite different proposition.


I note also that you seem to be talking about EV battery packs -- many feel that they are not suitable for use on a boat. LiFePo4 storage is quite a bit less dense than EV LiIon packs.


The main thing with all questions like this -- is to look hard at the facts and do the math. Don't let wishful thinking cloud your judgment.

[KTP]

I think the new Trojan Trilliums that are coming out in early 2019 are about 12.8V nominal at 93ah for around $650 each (with all sorts of safety and monitoring stuff). They are rated for something like 4000 cycles to 100% DoD but probably more realistic to say 2000 cycles. Probably around 1000 watt-hr usable per battery to get more cycles. Finally, something that is made by a big boy manufacturer with a warranty and all. Safe technology compared to some Li-ion.

20 of those would be $13,000 (maybe there is a volume discount though?) and would give you 23.8kwh or about 20kwh if you stayed a little away from each end. They are 27 pounds each, so the total weight would be 540 pounds, which is not that much really. If you are all electric, you have probably pulled out way more than that in engine, fuel tank and auxil equipment.

No more oil changes, sea water filter clog, impeller disintegrating, dirty contaminated fuel.

It is a bit on the expensive side, but with new 40 foot sailboats costing $500,000, it isn't outrageous.

[skipmac]

Originally Posted by KTP

I think the new Trojan Trilliums that are coming out in early 2019 are about 12.8V nominal at 93ah for around $650 each (with all sorts of safety and monitoring stuff). They are rated for something like 4000 cycles to 100% DoD but probably more realistic to say 2000 cycles. Probably around 1000 watt-hr usable per battery to get more cycles. Finally, something that is made by a big boy manufacturer with a warranty and all. Safe technology compared to some Li-ion.

20 of those would be $13,000 (maybe there is a volume discount though?) and would give you 23.8kwh or about 20kwh if you stayed a little away from each end. They are 27 pounds each, so the total weight would be 540 pounds, which is not that much really. If you are all electric, you have probably pulled out way more than that in engine, fuel tank and auxil equipment.

No more oil changes, sea water filter clog, impeller disintegrating, dirty contaminated fuel.

It is a bit on the expensive side, but with new 40 foot sailboats costing $500,000, it isn't outrageous.

Maybe I'm doing the math wrong but that doesn't sound like much for a propulsion system. On a 40' boat I would think it would need at least 20-30 kW motor to power the boat. Assuming best case scenario: no wind/current and motoring slowly you might use 7-10 kW (about 10-13 HP). So you would have 2-3 hours motoring with a $13,000 battery set up?

Then how do you plan to recharge that bank? Will take a LOT of solar panels or you can install a diesel generator but will then have to change oil, filters, impellers and the like.

[KTP]

Originally Posted by skipmac

Maybe I'm doing the math wrong but that doesn't sound like much for a propulsion system. On a 40' boat I would think it would need at least 20-30 kW motor to power the boat. Assuming best case scenario: no wind/current and motoring slowly you might use 7-10 kW (about 10-13 HP). So you would have 2-3 hours motoring with a $13,000 battery set up?

Then how do you plan to recharge that bank? Will take a LOT of solar panels or you can install a diesel generator but will then have to change oil, filters, impellers and the like.

Yeah that is probably about right. 7 to 10kW would get you going around 4 to 6 knots in a 40 foot boat depending on wind and seas. So about a 8 to 15 mile range at that level. If you were to drop back to 2kW and go 3 knots, you could get a 30 mile range.

I think it is for either the type of people who day sail and just need to motor a few miles each way to get to the open water and wind or for people who plan their trip around the weather and also don't have a schedule to keep (that is us).

My hope is stuff continues to get better and for 1000 pounds and $10k you can have something like 60kWh, getting you up to the 50 to 100 mile range in some conditions.

[bluenomads]

Originally Posted by KTP

20 of those would be $13,000 (maybe there is a volume discount though?) and would give you 23.8kwh or about 20kwh if you stayed a little away from each end. They are 27 pounds each, so the total weight would be 540 pounds, which is not that much really. If you are all electric, you have probably pulled out way more than that in engine, fuel tank and auxil equipment.

Even re-powering, let alone new, the weight isn't a problem for a 42' plus I think. For us, we would take out 600kg of diesel (engine 1), 600kg of diesel (engine 2), 350kg of diesel (old generator) and replace with 100kg of motors, 180kg of DC gen, and the rest could be batteries (but don't need to be!). Oh, that those figures don't count the reduction gearbox or other parts too...

[sstuller]

Providing electric propulsion for power boats is considerably more difficult than sailboats. With sailboats you have the thrust of the sails as part of your power picture. Power boats have to rely on the engines for 100% of their thrust.



If you divide the hull drag into two parts, frictional and wave making, with sailboats the easiest approach is to let the electric drive make up for the frictional resistance and let the sails deal with the wave resistance. The friction losses are modest compared to the residual (wave - making) losses.



This approach simplifies the power calculations. The individual sailboat owner has to decide which side of the power problem he wants to deal with - sail or power. Thanks.

[KTP]

I think we will be doing some testing of that this spring (we are currently getting the finishing touches on the electric motor install and then will work on replacing some rigging). Our hope is that motor sailing and pointing a little closer to the wind becomes very viable at low current draw. Also sailing in light winds with a little help from the motor. The prop turns at 2 amps 48V which is only 100 watts. At 10 amps it is straining on the dock lines (500 watts). If it is a calm light air day I am thinking having the motor going at 500 watts with the sails catching what air they can might move you while still maintaining the peace and quiet of sailing vs a diesel engine idling at 800 rpm.

I mean part of sailing for me is about being quiet.

[skipmac]

Originally Posted by KTP

I mean part of sailing for me is about being quiet.

That is one of the things that first hooked me on sailing. Never been sailing, went out as crew on a delivery to the Bahamas. Leaving port under power it was like meh, just a boat. Then we cleared the channel, hoisted sail and turned off the engine and magic.

Regardless of the criticisms and skepticism I express on most the threads on electric I would really love to go electric for the quietness, I could eliminate my v-drive and have better access to the stuffing box and shaft log. But I don't want to give up the range and don't want to pay 2x or 3x to go electric plus large generator to get the range back.

[sstuller]

Re KTP #367 during the day motorsailing with low amp draw your solar panels may provide enough output to eliminate any battery drawdown. Thanks.

[Capt. Arnaud]

It is possible to have an electric propulsion system "only" depending on your navigation and electric "needs".

I hardly use electric instruments, once in a while Open CPN to check position but no radar or AIS. The depth sounder only for anchoring.
Anchoring under sail when possible, so I calculated my electric system for optimal regeneration and only to motor slowly in and out of harbors.

I have only 2 solar panels and a wind generator for the 12V system so regeneration is very important for the 72V system.
With a 3 to 1 pulley reduction gear the motor is not pushing very fast but has a lot of torque on the propshaft to push my 30 ton boat.

The system starts generating passing 3 kn but just enough to maintain voltage.
But when sailing at 5kn it regenerates 1.4kw so when the 72V battery bank is full, the 72V-12V DC-DC converter helps to charge the housebank.

It comes all down to what makes you happy, if I didn't had to enter harbors once in a while I would be happy enginless ;-)

[KTP]

Capt, what size is your battery bank for that relatively large boat?

Eventually I would like to have about 20kWh, which would certainly get me in and out of most harbors and marinas plus be a decent size to run the house equipment. Initially we only have about 12kWh for testing.

[Capt. Arnaud]

My bank is really the minimum possible, we only have 7.2kWh
but for me here in Ecuador, the harbors are so small that I have more than enough power to enter or exit the harbor, of course we also start sailing as fast as possible and almost sail back in.
If a harbor is bigger you can actually often sail in most of it as I did in Marina del Rey, California.

I'm just back from a whole day chartering, motored out of the harbor but sailed into a bay and anchored under sail and in the afternoon weighted anchor by hand (even if we have the power I like to save it) and sailed out of the bay.

I don't want to spend too much on batteries yet because I don't need more at the moment and because batteries are so inefficient that I find they are not worth it yet.

Well I have to mention that I'm talking about my 72V battery system, I have a separated housebank which I can charge by solar, wind and from the other bank by regeneration of the motor.
To regen I have to sail at least at 5kn to make it interesting.

[nevetsyad]

All of this talk about full throttle. Pushing 12kW all day for days, cruising at 6-8kts, that's not the target audience or where EP shines. A decent 500+ watt solar bimini on a 30 foot cruiser will push it day and night at 2-3 knots, for forever. Becalmed for days while crossing an ocean, do you burn diesel for days until the wind starts back up, or make 50 miles of progress a day, silently? Low speed cruising is where solar/electric sailboats are amazing.

If you're in a hurry, it's not for you. Hell, sailing probably shouldn't be for you. I look forward to the day I can putz around the islands under sail and occasionally make 50 mile silent jumps under motor-sail, all without ever worrying about where to get fuel at next. Maybe even cross and ocean, pushing a knot or two at the prop while keeping the batteries full.

[KTP]

Yes, it is the silence and lack of smell of oil and fuel which attracts me to EP.

If I wanted to motor all of the time I probably would not have gone for a sailboat. I HATE the sound of a diesel droning on and on. I don't like waiting for it to warm up either.

[OldMan]

Originally Posted by nevetsyad

All of this talk about full throttle. Pushing 12kW all day for days, cruising at 6-8kts, that's not the target audience or where EP shines. A decent 500+ watt solar bimini on a 30 foot cruiser will push it day and night at 2-3 knots, for forever. Becalmed for days while crossing an ocean, do you burn diesel for days until the wind starts back up, or make 50 miles of progress a day, silently? Low speed cruising is where solar/electric sailboats are amazing.

If you're in a hurry, it's not for you. Hell, sailing probably shouldn't be for you. I look forward to the day I can putz around the islands under sail and occasionally make 50 mile silent jumps under motor-sail, all without ever worrying about where to get fuel at next. Maybe even cross and ocean, pushing a knot or two at the prop while keeping the batteries full.

Day and night? Solar doesn't generate anything at night.


Do you have experience with 500W push a 30' boat @ 2-3kts?