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S/V Oasis is going to convert to electric motor from Universal diesel
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Jonathan Oasis
S/V OASIS
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August 22, 2020 - 2:19 pm
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The time for electric motors in sailboats is upon us.  In talks with a marine electric motor company, they have given me the following general electric motor conversion specs for my Downeaster 32. 

 

This means removing the existing Universal diesel which runs like a champ.  I will be converting S/V Oasis to electric motor-hybrid system with generator in the next year or so (hard to say when, sooner is better).  This is a big project which has to include replacement of electrical systems, charging, inverter, new solar (& placement of solar panels, i.e. dodger), etc.

 

48V, 20 kW electric motor (16 kW continuous).

Motor type PMAC Brushless.

Motor Weight 135 lbs.

Motor air cooled.

Direct to shaft (no transmission).

Physical size of the electric motor in the engine room is within 20" h x 20" w x 25" d. 

 

Use either Lithium batteries (LiFePO4) or AGM Group 27 batteries.  AGM is significantly cheaper.  Upgrade AGM batteries in the near future when new Lithium battery technology is released, since Lithium is continually, rapidly developing.

Total battery bank size needed is 17 kW.   Typical bank size is between 300 Ah - 500 Ah (48 V).

With a small gas generator (2 kW), can obtain "unlimited" motoring range if speed is less than 2.5 kt  (engine at 960 W, 20A).  Of course this measurement likely assumes flat water and used hull speed of 6.8 kt (a speed which I have never achieved even with freshly painted hull and max diesel throttle!).

Typical power-trade-off motoring speed running on battery only would be a bit above 4 kt.

 

From general reading it sounds like power regeneration becomes efficient only starting at around 4-5 kt so the typical under-sail regen from the motor, I'd assume, is only about two or three lightbulbs worth (50 - 100 W).  i.e. Regen could easily replace all power used by nav instruments but not the power used by a fridge.

 

The big question is how the power system can support long-range cruising in waters where the motor needs to assist or be primary propulsion.  Where winds are very light to none and solar is also tempered while current is strong, such as, coastal Alaska; or alternatively, where winds are very light to none or worse contrary, while solar is heavy, such as, Baja MX; or finally, where motoring is absolutely required and both tides & currents are strong, requiring scheduled motor-sailing time tables, such as, long delta waterways (east coast equivalent might kind of be the ICW).

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Scott Carle
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August 23, 2020 - 9:15 am
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Ok you need to document this really well. that will be a great project that a lot of others will be really interested in.

 

Ok... I am going to throw in a few comments and observations here. they are worth as much as you have paid 🙂

Batteries

The batteries.. those are some nice batteries... Right now the iron phosphate lithium are the safest, most cycles, highest discharge batteries out there that are in production that any consumer can get. They also do well in a warmer hotter environment without damaging themselves due to overheating. They and this is the biggest thing don't thermal runaway and catch fire like some of the other lithium chemistries. Price does hurt but they will probably last the rest of your life.

I have seen some people that have used them from https://lionenergy.com/

The manual for their 100ish amp hour capacity 12volt unit has a minimum 3500 discharge cycles under abusive charge discharge conditions. But if you baby them much higher. I think the 3500 is their warranty cut off. I have heard but cant find on their website that you can expect about 10,000 cycles out of them. I will say that since I first heard about them their site has gotten much slicker and the details about the batteries has gotten much less. Not sure what that is about. A bunch of companies make them though..I was just looking at some made by Victron and I like them as a company. I have several of their battery monitoring products on Valkyr for the current battery bank.

Solar

How much solar are you looking at? we have 500 watts on Valkyr. 225ish watts on the hard dodger and 190ish over the dingy davits.  It has worked well for us. I have thought about expanding capacity some and the only reasonable place I can think of is some external to the rear railing around the cockpit that folds down on the outside when underway sailing but can be pivoted up at anchor or even when motoring. I figure you could get another 500ish watts on her maybe 1000 if you worked it right. If you stayed with really high efficiency, my 500 watts would be closer to 750-1000 watts. My panels are nothing to write home about  with the ones on the cabin being less than 10% efficient and the one on the dingy davits probably closer to 14%.. Good ones are pushing 20% nowadays. That is an expensive battery bank... for 300 amphr at 48v in LiFeP04 thats right at 10,000.. if you have a supplier for a better price than that you need to share 🙂

 

with 1500 watts of solar.. your theoretical charge capacity is 31.28 amps at 48volts. realistically a great day might get you 20 amps. One thought is what speed can you get with a 20amp current to the motor. If you balance it right you could run the motor sailing or not right at a neutral charging rate so that your battery bank stays charged and you just use the excess charging capacity to power the motor. Lots of interesting ideas 🙂

ok... pricing for solar is high if you just hire someone to do a turnkey job for you.. However you can get solar panels for 21 to 50 cents a watt from http://sunelec.com . they have a lot of factory second (cosmetic not functional issues), overrun, projects that they bought out the excess solar from etc.. even some used panels in good condition. You will have to dig to find exactly what you want in the way of voltage and efficiency. They also have new panels at still great prices 1 to 3 dollars a watt.. I never look at those much but if you really work hard on getting top efficiency panels that is probably where your going to go. I just looked and they have some 360 watt hundai panels for 49 cents a watt right now that are 18.5% efficient..  Those are some large panels (40x77 inches)so depending on layout maybe bigger than you can find space for. They have several brands right now between 32 and 50 cents a watt. They also have good deals on charge controllers and other stuff sometimes. I have found that they suck for support, even sales support but for that pricing it has been worth dealing with them for me. Another note on solar.. some of your panels are always going to be shaded. So you need to design the system such that it minimizes the negative effect of any individual panel being shaded. Here are a couple sites with a little about that on the linked pages https://blog.aurorasolar.com/shading-losses-for-pv-systems-and-techniques-to-mitigate-them/  https://thosesolarguys.com/does-solar-work-in-the-shade/

Generators

For long range power you need to up your generator, I am not a gas fan on the boat but it is what it is.. ether get a 4+kw diesel gen or stick with the 2kw gas and get two of them such as the honda's or other brands now that are quiet and stack/plug into each other to work in conjunction with each other. Sounds like you could get about 5 knots with 4 kilowatts of power. Something you could get one generator and add one or more later that will stack to spread cost over time. Gives you much larger capacity along with some redundancy.

I think if you push your solar as much as you can and also maybe look at some wind that you are going to be doing well. Direct drive connection to shaft is going to be simple and quiet but honestly im not sure about efficiency or heat generation. That is a lot of torque at low rpms. Most electric motors are a lot happier producing at higher rpms and then gearing down for the prop shaft. High power and low rpms also seems to me that it will produce a lot of heat. I haven't really been keeping up the last 5 years or so with the state of the art but last I looked that was my impression on what was available.

Overall power?

as far as power.. 20kw = 26.7 hp in applied power. The 32 came with a 24 hp engine and some upgraded to 27 hp... I would expect that with that electric engine that maneuvering and speed wise it will actually exceed the performance of a diesel all around other than as a system for range. Considering we never really use full rated power I would think it is going to work well. I'm not sure the difference in the 32 vs the 38 for hull speed from personal experience. I would expect for our 38 that that 20kw would get us to about 6 knts. with the 32 hp diesel we can push 7.4 to 8 knots on flat water. You will find that the boat will move like a champ from a stop as in take people off their feet at how much torque it can produce if you just go to full thrust. I would think you will go to a larger prop also which will make it even worse. Make sure the thrust bearings are beefy on the shaft. it will exceed by a lot what a stock engine can do.

if you have generators 2x2kw and 1.5kw solar.. just on them you can produce about 7-8 hp so about 1/3 power just under those conditions. I would say that using that plus the battery bank could extend your normal speed cruising range by 2x or more for motoring in high currents etc..  (what is your expected full power range with that setup?)

 

Regenerative

Um.. regenerative power is a nice thought. but i wouldn't even use it as a consideration.  I have never heard of anyone getting any usable amount of power out of regeneration other than catamarans that run 10+ knots under sail. You could probably get a decent amount out of a large tow behind generator setup designed for power generation at 2 to 5 knots of speed. I think it would be pain in your butt to manage though. Lots of moving parts and connection points with huge loads on them. A couple 250 to 500 watt wind generators that you just mostly ignore all the time would be a better return on investment as in cheaper and less hands on work. downside is constant background noise from them.

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Scott Carle DE38 Cutter s/v Valkyr
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jlynker
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September 5, 2020 - 12:08 pm
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Love that you're going Electric!

Years ago, in discussion with Nigel Calder at the Port Townsend Wooden Boat Festival, he highly recommended this company:

Scott McMillan
President/CTO
E L E C T R I C Y A C H T
http://www.electricyacht.com
C L E A N • G R E E N • Q U I E T
763-370-2610

Not sure where they stand today, but anything Nigel Calder has to say pops to the top of my considerations. DE38 is listed as one of the boats they have a suitable motor installation for:
https://electricyacht.com/find-your-boat/

Also found this information:
https://marinehowto.com/lifepo4-batteries-on-boats/

Hope this helps and Good Luck!

John

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Jonathan Oasis
S/V OASIS
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June 30, 2021 - 11:20 pm
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I have heard from the sales guy I have been talking to, that a Downeaster 32 near Newport Beach has made the conversion to electric, a 20 kW motor.   I still have this in my plans.  I will go with one of the Lithium battery vendors which is recommended by the electric motor company.

 

More pictures to follow.  It is a long term project and many other boat projects to take care of first.  

 

Last year (or year before? Lockdown has made time strange), the recommended local diesel mechanics gave me a rough quote of about $6,000 to fix (repack/replace) my stuffing box because "we'll have to yank the engine out, using an A-frame, and set it in the cabin forward, to get back there to work on it."   No way I'm going for that, although the stuffing box is very tough to reach being underneath the muffler and underneath the fiberglass battery shelf.   So in fact, converting to electric will save me a big hassle and/or cost in this regard. 

 

I crawled behind the engine today (inside engine 'room') to check out where I could place the 16 batteries.  There seems to be plenty of room (all sizes assuming Group 27 form factor): 

- the factory-made battery shelf holds 4 batteries on top of the shelf.

- the factory-made battery shelf has space underneath it, for at least 4 batteries, I believe.

- The fiberglass ledge to the port side of the engine (where I currently have a hot water tank-heater, just outside of the alternator) has a huge empty space underneath, at least 2 batteries can fit underneath the ledge. 

- 2 batteries can fit to the starboard side of the motor after engine is removed.

- 2 batteries can fit to the starboard-aft side of the motor after engine, diesel filters, and raw water intake are removed.

So that is 14 so far, and total of 16 (I believe) is needed, but there is still extra space to be found in nearby places. 

Which the many batteries can be:   a) mounted low in the boat for good center of gravity;   b) mounted aft in the boat for better weight distribution;  c) located very close to the motor for shorter cable run which saves $$ on cable and should also be better voltage efficiency.

Currently, Oasis has 4 batteries in a battery tray located under the small aft berth and 1 battery on the engine room battery shelf.  This was done by a previous owner I suppose to "allow easy access to water the batteries" but it still isn't much easier than the engine room shelf, and it uses the entire locker space, which is normally quite large. 

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Scott Carle
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July 1, 2021 - 4:48 pm
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So battery storage. On valkyr a DE38 we had a large space between the aft water tank and the fuel tank that would be a great place to put batteries. If you get rid of the diesel motor you can cut out the fuel tank and use that space also for batteries. moves the weight more toward middle of boat and lower.

 

Just a thought I always hated the location of the batteries on valkyr.

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Scott Carle DE38 Cutter s/v Valkyr
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Jonathan Oasis
S/V OASIS
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July 2, 2021 - 2:18 am
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The air-cooled electric motor is rated for 20 kW, the battery bank needs to match that, 48V at 400 Ah, recommended 19kWh total.   Any hints on the amount of solar real estate needed to charge a 19 kW bank in 24 hrs?  (Well, a 24hr day only having sun for half the day, and usable sun for less than that too, immediately puts a restriction on time.)    Or what size solar panels would be reasonable to start looking at for the DE32's available space?   Obviously a hard dodger needs to be added into the plan I guess. 

A quote from the engineering document for DE32 displacement & hull speed: "With a 19kWh battery bank, you will see a 20NM range at 4kts with reserve."

Ultimately I believe I will have to add a generator, which would be diesel, so the diesel tank will stay as-is, although the size of the tank is overkill, maybe I will also add a diesel heater to repurpose the tank too.  The generator would be one of the newer small box models.  Another quote from the engineering document:   "A 3.5 to 4.5kW generator may support a speed of 3.8 kts".    That means directly, the system becomes a hybrid vehicle, with the diesel generator powering the electric motor rather than needing battery, as long as power does not exceed about 3.8 kts.   I'm not sure how optimistic their engineering specs are, maybe it would be slower than that.    To reach near fastest sailing speed (5.5 kt) on generator alone would require a 10kW genset with this motor which is much too large to fit into a DE32 and too expensive anyways.   One of the portable gas generators (like the Honda one) supposedly allows the motor to push at 2.7 kt while the generator supplies 960 W from 20A. 

My previous post said, "Downeaster 32 near Newport Beach has made the conversion to electric, a 20 kW motor."   The vendor gave a new update to say that the build fell through.  So there is not yet a Downeaster which has made the switch to electric as far as I have heard.   Maybe I'll be first, like with my synthetic rigging?   In both cases, being early means much more expense.  The costs are getting more affordable rapidly so the early birds are paying the premium.

 If the diesel tank was removed (difficult in itself), and batteries put in that space instead, the one good thing about the lithium batteries is that they do not need ventilation or heat dissipation (supposedly).  One of my concerns has been whether it is appropriate to place the batteries below the level of the sole.  Because if water ever enters the boat due to unavoidable storm (more like:  when water enters the boat), the batteries should be slightly higher, to be protected and dry.   I believe this is why the battery shelf behind the engine is so high:  to keep the batteries safe.   But maybe with lithium, the batteries could be placed in a water-tight compartment, with a vent which reaches higher up.  Then, any water ingress doesn't destroy all power on the boat.  Very important if it happens on a voyage.

 

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Scott Carle
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July 3, 2021 - 2:31 pm
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Throwaway thoughts

Solar.. To get a full 19kwh charge on a average day I would think 4kw of solar. I don't see you realistically fitting that much on there.  You could realistically fit 700 or 800 watts on a hard dodger. 300 over dingy davits and have 600 port and 600 starboard hanging on hinges on the push pit which you would need to extend a little forward to give you enough length. 300 ish watt panels are average 36 inches by about 5 ft in length. You could also build a arch over pilot chair that main boom traveler goes on and extend it a bit aft to put another 600 watts or so on. It would clean aft cockpit up on deck 🙂 and give you places to attach nice enclosure for rain etc.. that brings you close to 3000 watts.. or 3kw  .. you might on a miraculous day get 2.8kw out of it. so maybe 2.8 x 8 hours of reasonable sun will give you about 22 kw hrs. You will not get that. The panels on the dodger are constantly being partially shaded by boom and mast. Any all the ones aft of there will do pretty well.. but will only get max capacity which is still not whats advertised for about 4 hours nearest noon or sun over head in the summer. Winter you lose some capacity as all your panels will be mounted repetitively flat. I think based on my experience if you got 3000 watts of solar installed in those locations that you would get about 10 to 12 kw hrs a day.. so figure a day and a half to charge batteries from a 100% discharge. However if you are using lead acid your only going to 50% at most before you destroy the batteries. Even LiPO that you can technically discharge to 100% you shouldn't.. at most I would do 80% and as a rule would keep it to 50% on a normal day. You absolutely want a MPPT controller or even better a pair of MPPT controllers that can work together or switched between to give some redundancy. Normally I would say maybe more expense than needed but if it affects your primary propulsion I would go for redundancy.. Also over spec all the wiring. If someone installs this for you they are going to go by standard wiring recommendations. Which are around a 5% drop.. this causes heat and losses at the end of the cables. If you over spec everything from the solar to charge controller, charge controller to batteries and especially batteries to engine you will over all gain a couple percent efficiency through the whole system and make any possibility of overheating of components much less. Lots of tricks you can do.. Do protect at appropriate places with circuit breakers... I'm not a fan of fuses that I have to physically replace. If something happens that throws a breaker but I need go juice right the "Blank" now I would like to be able to flip a switch and run a reduced capacity if I can  versus having nothing. On valkyr every single battery + cable had its own independent circuit breaker so that if a battery died or was giving problems I could remove it and run on 3 batteries instead of 4 etc... with a 48volt system that is going to be harder to due unless you have each battery being 48 volts. However you get the idea. If I had a 48 volt motor I would try and build a 48 volt electrical system and then run a 12volt inverter to pull power out for house loads. There is the potential with the correct motor that if you batteries died or your charge controller died that you could with the sun shining feed power directly from solar to motor for limited power. Ok.. my head is hurting so I am going to assume yours is to at this point.. a lot of things to think about.

 

Generator.... i have seen more than one write-up of 30ft ish and smaller electric boats able to run off a small Honda generator at 3 to 4 knots. A couple of the new generation stack-able generators at a couple kw each that you can use one or both to double your power output would be a great system other than dealing with gas 🙂 most of them are now 4strokes and run very quiet. Honda's being exceptionally so.

 

I would go to the trouble of creating a waterproof box for the batteries.. Maybe just build it in using the inside sides of the keel space there as part of the box. make sure to leave more than adequate drainage past/under it though. Access will be great. I am proof that flooding can happen. standard sealed batteries would not be hurt going underwater.. however any more advanced one would be as they almost all have electronics/circuit boards integrated nowadays.

 

Also your chargers, shore, solar, inverters etc.. should all be as high as you can get them. I would recommend high up on the starboard side inside the engine compartment on the bulkhead between the pilot berth and the engine compartment and against the end of the foot well facing out the engine compartment when companionway steps are opened.

 

With the engine out and that area cleaned up and a much smaller electric motor I'm wondering what you could do with that area? another little pilot berth back there. The ability to put a grate in you can walk on to get back there?

 

I have seen companionways modified so that the hing on the starboard side instead of lifting up and attaching to the cabin top when up.. It makes it easier to access that space and leaves companionway opening clear when your in the engine compartment. The one I saw had a 4 or 5 ish foot piano hinge same as comes standard but longer to fit a side opening companionway ladder instead of a lifting one. Instead of the latch on overhead to keep it open it had one on the chart table to hold it against the chart table in the open position.

 

Speed... you want to run the biggest prop you can and gear the electric motor down so that at max output it is turning that prop the most efficient calculated rpms. Electric motors will kick your diesels ass at torque which allows you to run a bigger prop..... BUT.... you have to gear it so that it doesn't strain the electric motor at full output and cause it to over heat. It's a balancing act. Some sort of active cooling shroud ducting air around the motor would be a nice feature I don't see people doing in their electric conversions. Make sure that any motor  you get is rated at 100% duty rating. Or that your usage allows you to de-rate it to a setting that allows it a 100% duty rating. Unless you get a folding prop or even better a folding and tilt adjustable prop you are going to lose some sailing speed to the drag unless you let it free wheel and maybe even run your electric motor a a couple % to remove drag. There are some really interesting things you can do with an electrically driven prop like using it under sail at 5 to 10% capacity that you don't notice it running but it gives you a 1/2 not better speed and allows you to point a few percentage points higher due to the extra air flow over the sails. Don't get caught do that while racing 🙂 lol.

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