# Future sailboat conversion



## patric (Aug 1, 2021)

Hello,

I'm currently looking around to buy a sailing-yacht and plan is to convert slowly convert it into a electric/hybrid setup and need some advice. Writing a long introduction to convey my initial thoughts and ideas, and what i see as possible issues.

What i'm currently looking for is a ~40-45ft steel yacht (~14000-16000kg). Fiberglass would be lighter, but my preference is steel due to a multitude of reasons.
I will be looking for boats that have no functioning motor or that will need a replacement soon since that will reduce the price quite significantly. ( 10k EUR or so for a new diesel motor and all that it requires )

My use-cases are:

Silence .....
Large enough battery-bank to switch to using induction cooker / electric owen.
Allow to stay offgrid for much longer periods. (Electric watermaker etc)
Motoring in and out of marinas/setting anchor and such.
Instant engine power and much lower, steerable, speeds possible.
Higher reliability of a electric engine for propulsion so even if the genset breaks there would be enough time to get to a safer place (drop anchor etc)
Have a large enough battery bank that would cover at least a week without sun or running the generator. (~5kWh per day ~35kWh for a week )
Genset to allow recharging as a fallback when without sun.
Genset to allow longer distance motoring, even if a bit slow.
Since there is no need to think about propeller-shaft etc i could place the genset and fuel-tank wherever i want, like on deck in an encapsulated box.

Power to propel a boat like this at hull-speed would require somewhere between 25-35kW but lower cruising speed would only be 3-8kW, in light wind, when up to speed.

Target RPM for the prop should be around 800-1000rpm

Batteries i'm thinking about are reclaimed Tesla 5.3kWh modules from a 85kWh pack ( 225Amp continuous, 22.8V nominal, 25.2V max ) and 12 to 14 modules depending on selected voltage and such.
48v - easy to source components for marine environments but having issues locating sensibly priced motors/controllers. [email protected] = 625A
96v - still possible to source components, but starting to be difficult. Starting to be easier to locate BLDC / AC motors ... [email protected] = 312A
144v - quite hard to source components, but starting to be easy to source motors.. [email protected] = 208A
168v - very hard to source components, but starting to be easy to source motors.. [email protected] = 178A

All the above variants should be possible to handle with the tesla battery modules. (Max current for 30kW used in calculations)
48V = 14 modules in a 2s7p setup would result in 89A (max) per string
96V = 12 modules in a 3s4p setup would result in 78A (max) per string
144V = 12 modules in a 6s2p setup would result in 104A (max) per string. If one string fails the remaining string will have to provide 208A and that is also quite doable.
168V = 14 modules in a 7sp2 setup would result in a 89A (max) per string. If one string fails 178A is still doable on that string.
I do prefer having 3 or more strings for redundancy (failing Pack/BMS/cables etc) since this would be a combined house and engine-bank. Each string should be individually fused and possible to isolate from the rest in case of a fault.

Power generation would consist of multiple setups:

Solar ~1kW of usable ( ~2kW but only half would probably be usable depending mast-shade etc )
Hydro generator ~200-500W when sailing. ( preferably via regen of the motor instead of a drag-able generator)
Diesel generator(s) .. 1 or 2 generators with a capacity of ~5-6kW each.

Still researching solar-panels and how they could be setup, but 4x400W panels on the back arch + 2x400W that are manually moved around when at anchor. 4 panels @ 45V = 180V so on the edge if going with a 168V battery-pack.
144v and below should be doable either way, but still hard to source components. Possibly finding a _good_ MPPT charger with boost functionality, have so far only found crap Chinese versions with contradicting specifications.

If we go the other way and only do 48v for everything we should be able to use known quality brands of MPPT controllers, 220V inverters and all the other stuff needed on a boat, and possibly reusing what's already installed.
One possible motor could be the [email protected] (28kW) :





Affordable Electric Vehicle Batteries & Components from Electric Car Parts Company


Electric Car Parts Company is your one-stop-shop for affordable electric vehicle parts and components including batteries. Shop our selection and order now!



www.electriccarpartscompany.com





One thing i have been looking for, but have not found any so far, is if there are any AC or BLDC motors with thru-shafts that could enable stacking multiple 48v motors together, but not sure on how complex the controller setup and such would be in that setup, especially with regen.

Solarpanels / MPPT chargers / 220V inverters / generators etc are still required and not included in the total price of this conversion, if we stay at 48v.

Rough estimates of prices, if i go 48V with the AC motor i linked to:
Tesla battery modules ~1000EUR each if buying 12-14 modules. ~14000EUR.. Have not search too much yet so may be possible to get cheaper.
BMS 100EUR - reusing the built in Tesla BMS boards and only adding a controller.. ( See GitHub - collin80/TeslaBMS )
contactor(s)/fuses/cables etc ~2000EUR
= ~14000 + 2000 + 100 + 10% = ~18000EUR
+ whatever motor + mounting is needed ~2500EUR
So a total of somewhere around 20,000EUR should be possible.. Maybe a bit lower if finding cheaper Tesla modules or going with less capacity.


.... So now... Tear my ideas to pieces and suggest other things that would work better or would be cheaper!


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## brian_ (Feb 7, 2017)

This looks like an interesting project. 

It isn't a big deal, but the assumptions seems to be that Tesla modules are 24 volts nominal; they're not - they're 22.5 V nominal.

Similarly, the actual voltage of solar panels: for effective charging, you need the output voltage of the panel combination at maximum power in realistic sun conditions to be close the fully-charged (not nominal) voltage of the battery, and the output voltage at open circuit in realistic sun conditions to be higher than the fully-charged (not nominal) voltage of the battery. As with batteries, panels don't have just a single constant voltage.


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## brian_ (Feb 7, 2017)

patric said:


> One thing i have been looking for, but have not found any so far, is if there are any AC or BLDC motors with thru-shafts that could enable stacking multiple 48v motors together, but not sure on how complex the controller setup and such would be in that setup, especially with regen.


Stacking multiple motors means using the same multiple of controllers/inverters.

There are some hollow-shaft stackable AC motors, and others that can be stacked end-to-end with couplers, but I don't know if there any that are intended for such a low voltage, since few vehicles larger than a golf cart use only 48 volts. Perhaps the practical solution is to use a single motor which is intended for a moderate voltage (~100 to 150 V), and is large enough that even at ~48 V it can produce the required power.


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## cricketo (Oct 4, 2018)

brian_ said:


> This looks like an interesting project.
> 
> It isn't a big deal, but the assumptions seems to be that Tesla modules are 24 volts nominal; they're not - they're 22.5 V nominal.
> 
> Similarly, the actual voltage of solar panels: for effective charging, you need the output voltage of the panel combination at maximum power in realistic sun conditions to be close the fully-charged (not nominal) voltage of the battery, and the output voltage at open circuit in realistic sun conditions to be higher than the fully-charged (not nominal) voltage of the battery. As with batteries, panels don't have just a single constant voltage.


I would add that for PV systems the open circuit voltage shouldn't be targeting the battery pack voltage directly, but rather the charge controller's operational input voltage. Then, charge controller should be the one also be matched to the battery pack on the output side.


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## patric (Aug 1, 2021)

brian_ said:


> This looks like an interesting project.
> 
> It isn't a big deal, but the assumptions seems to be that Tesla modules are 24 volts nominal; they're not - they're 22.5 V nominal.
> 
> Similarly, the actual voltage of solar panels: for effective charging, you need the output voltage of the panel combination at maximum power in realistic sun conditions to be close the fully-charged (not nominal) voltage of the battery, and the output voltage at open circuit in realistic sun conditions to be higher than the fully-charged (not nominal) voltage of the battery. As with batteries, panels don't have just a single constant voltage.


Yea.... Been spending some time thinking and reading, but do not have too much practical experience in the EV field, unless you count my DIY electric bicycle 

Good reply, and forced me to fill in some more details i was assuming everyone already knew. 

The Tesla modules can be a bit tricky, but as long as the controller is fine with those voltages i _think_ it should be fine.... But maybe some controllers are more fuzzy than others?
For a string with 2 modules you will have something like the following discharge curve. A discharge rate of <0.5C should help too.
39.0V @ 0%
41.1V @ 10%
48.2V @ 20%
52.2V @ 50%
56.3V @ 90%
56.9V @ 100%








What's the battery voltage from 0% to 100%?


Battery voltage in the manual is listed as "nominal 350 volts", but that's not the numbers it has at 100% charge and 0% charge. What are those numbers?




teslamotorsclub.com




Tesla have changed chemistry over the years so will depend on the exact full pack i will get..

Probably a good idea to never run the motor, without a generator running, if batteries are less than 25% anyway..
And should probably limit duty-cycle to be 10%->90% or so to make them last a bit longer.. 80% of 85kWh is still a crap-load of power.. 

For solar i'm still browsing around to see what's available, and what make sense in price. There are some 96 cell panels out there with Vmp of ~50V and some 72 cell with a Vmp of ~40V

Random 96 cell solarpanel:





Wholesale 500w 500 Watt Monocrystalline Solar Cells Solar Panel Manufacturer,500w 500 Watt Monocrystalline Solar Cells Solar Panel Manufacturer Suppliers


Here you can find 500w 500 watt Monocrystalline solar cells solar panel manufacturer and solar panel from Sunway Solar. Our products are sold to all over the world.




www.sunwaypv.com




This one has a I-V curve that breaks off at around 30V so 2 in series ~60V in low light conditions...
But yea, selecting solar-panels is tricky especially before you have actually decided on the actual battery-voltage, charge-controller and other related things.


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## patric (Aug 1, 2021)

brian_ said:


> Stacking multiple motors means using the same multiple of controllers/inverters.
> 
> There are some hollow-shaft stackable AC motors, and others that can be stacked end-to-end with couplers, but I don't know if there any that are intended for such a low voltage, since few vehicles larger than a golf cart use only 48 volts. Perhaps the practical solution is to use a single motor which is intended for a moderate voltage (~100 to 150 V), and is large enough that even at ~48 V it can produce the required power.


Any links you, or anyone else, could share? Blind searches for AC / BLDC motors mostly gives links to random aliexpress / alibaba shops with insane values that change multiple times within the same specification for a single motor.. =)


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## cricketo (Oct 4, 2018)

patric said:


> And links you, or anyone else, could share? Blind searched for AC / BLDC motors mostly gives links to random aliexpress / alibaba shops with insane values that change multiple times within the specification for a single motor.. =)


If you don't mind Chinese vendors, one may be worth considering is Golden Motor electric propulsion outboard,electric propel outboard, hub motor,brushless motor, BLDC motor,electric outboard,GMX motorcycle,Golden GMX,Electric motorcross,electric motorcycle,EZ Outboard, EZ-Outboard, EZ Outboard Motor,wheelchair conversion kit,foldable electric wheelchair,gearless wheelchair motor,portable electric wheelchair - they have a few motor variants that are claimed to have decent power ratings for a project like yours. The other usual suspect would be Motenergy, they're US based I think, but the motors are made in China too Motenergy Brushless DC Motors


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## brian_ (Feb 7, 2017)

patric said:


> And links you, or anyone else, could share? Blind searched for AC / BLDC motors mostly gives links to random aliexpress / alibaba shops with insane values that change multiple times within the specification for a single motor.. =)


I would just check the HPEVS and HyPer 9 performance curves, not because those are the best motors, but because they're readily available in substantial sizes. All of the eBike/quadcopter stuff is hard to pin down to good objective data, and they're mostly really small.

I'm sure there are lots of good products from legitimate manufacturers, but they really only want to work with OEMs so there's no good data for an individual doing a project. Even the HyPer 9 isn't built by NetGain, but by a company (SME) who supplies motors for industrial vehicles and publicly publishes no data for their products; that company is now part of Dana Spicer Electrified, so they're even less accessible. 

Strangely Parker does publish full specs for their Global Vehicle Motor series of PM AC motors, and some DIY projects have apparently used them. Even their little 142 mm line would be powerful enough (in the right length, with the right winding selection) and is available wound for 48 V (with various winding options to suit different operating speeds), although you would need a reduction drive to match the prop speed.


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## patric (Aug 1, 2021)

cricketo said:


> If you don't mind Chinese vendors, one may be worth considering is Golden Motor electric propulsion outboard,electric propel outboard, hub motor,brushless motor, BLDC motor,electric outboard,GMX motorcycle,Golden GMX,Electric motorcross,electric motorcycle,EZ Outboard, EZ-Outboard, EZ Outboard Motor,wheelchair conversion kit,foldable electric wheelchair,gearless wheelchair motor,portable electric wheelchair - they have a few motor variants that are claimed to have decent power ratings for a project like yours. The other usual suspect would be Motenergy, they're US based I think, but the motors are made in China too Motenergy Brushless DC Motors


I have read about Golden motor a bit, but have not seen any high-power BLDC motors @ 48v. If you go to their 20kW motors they are only listed at 72 or 96v.. They do list a couple of their BLDC controllers 48v @ 600A, but no motor to match, and no specification if it's only peak or continuous, but i suspect it's only for peak since it's not watercooled, and at 95% efficiency it would have to dissipate 1440W.

Wanting to have ~25kW @ 48v is tricky... but tankful for all suggestions and recommendations.

Have looked at 48V Electric Motor ISCAD V50 ⚡ E-Mobility Revolution 🛥 that claims to have a 50kW (!!!) @ 48v, but don't really trust those numbers since they don't present any efficiency numbers or 3'rd party reviews..

The only place i have found, so far, with something that's close to the requirements





- AC Induction Motor Drive Kits - Motor Drive Kits (DIY) - DRIVE SYSTEMS







www.electricmotorsport.com




But they are US based and i'm EU based, but maybe i can find a reseller..


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## cricketo (Oct 4, 2018)

I think you should seriously consider going with higher voltages. Even those 600A controllers likely can just briefly support those currents, while being rated only for 200-250 continuous amps. Your wiring and pretty much every electrical component for 600-700A would also be quite crazy (expensive) and difficult to work with. So 96V system would probably be a better choice.

Now, if you go with 96V, I would also suggest looking at... Zero motorcycles, especially SR or DSR models. They've got 28s battery packs with nominal of say 104, but they run on Sevcon Gen4 controllers (size 6 for DSR/SR) which can be easily adjusted for your slightly lower voltage if necessary. I even doubt that will be necessary. So the idea is find a bike that either has a nearly dead battery pack, or a bike that has been crashed, and start from there.


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## patric (Aug 1, 2021)

cricketo said:


> I think you should seriously consider going with higher voltages. Even those 600A controllers likely can just briefly support those currents, while being rated only for 200-250 continuous amps. Your wiring and pretty much every electrical component for 600-700A would also be quite crazy (expensive) and difficult to work with. So 96V system would probably be a better choice.


I know, but the cost increase to use 96V for other critical systems on the boat is also quite high and adds some other things that needs to be considered. Stuff at 48V and below is mass-produced and the stuff over is usually custom in the marine world... If your wallet ever hears the word "custom" and "marine" in the same sentence it will most likely start crying and run away from you.. 

This is why i brought up the question regarding 48V motors with a thru-shaft... This way two 15kW ([email protected]) engines could be used to provide a total of 30kW output power, and if one fails you would still have some engine-power left. But i'm leaning towards belt-drives more and more due to the fact that i still need to reduce the RPM of most motors i can find. (800-1000RPM on the shaft)

Some AC controllers do seem to support being put in parallel to provide a more Amps to the motor. Need to do some more research, but starting to think that multiple motors/controllers is the way to go if i'm unable to go above 48v.



cricketo said:


> Now, if you go with 96V, I would also suggest looking at... Zero motorcycles, especially SR or DSR models. They've got 28s battery packs with nominal of say 104, but they run on Sevcon Gen4 controllers (size 6 for DSR/SR) which can be easily adjusted for your slightly lower voltage if necessary. I even doubt that will be necessary. So the idea is find a bike that either has a nearly dead battery pack, or a bike that has been crashed, and start from there.


If it only was that simple i would jump at a 96V system... 
Going with a repurposed bike-motor and custom system for everything is nothing i would like to do since that would be a fully custom system with few or no replacement parts. The RPM would probably be quite high for powering a propeller...
You can find 96V controllers/motors, if you check the links posted, rated up to ~40kW, if i remember correctly, for around $3000 complete with a controller and liquid-cooling.

Then you also have other things such as DC-DC converters, 220v Inverters, MPPT chargers used on the boat needs to be rated for marine-use. Either a DIY conformal coating or have a official IP rating, and i would advice against DIY stuff for critical systems on a boat.

You also have to factor in that all these would need to support a input voltage-range of 80V to 113V to cover 80% of the battery capacity and that reduces the available devices even more.
This would also put requirements on the solarpanels where each string would need to be 4x 96 cell panels to have enough voltage for charging the batteries efficiently. Any shadows from the mast would greatly reduce the efficiency of all panels.

You do not want to rely on your bilge-pumps or navigation-lights being powered by a DIY conformal coated DC-DC step-down you now have zero warranty on and that your insurance company can have as an excuse for not paying out a cent for when your boat sinks or burns up.

You can mange if the engine fails or runs at a lower capacity on a sail-boat since you can always use your sails to get to a point where you can anchor, but you do not want to loose your capabilities to be seen (AIS and navigation-lights) or your capability to communicate (radio) or your capability to pump out water with the bilge pumps in case of a leak or a big wave crashing into the cabin.

You also have to factor in the requirement that all terminals that MAY present >50V has to be covered during normal maintenance. This is due to a boat being classified as a residence... EU and US rules seems to be quite similar in regards to this.

And what happens when something fails and you are in a different country where you only have access to "standard" marine equipment..

Yea, would be nice with 96V but unless i can find a solution where replacements of critical systems would be commonly available, in most places or by overnight shipping, i will have to stick with 48V sadly.


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## cricketo (Oct 4, 2018)

I am not going to dissect every line of your argument as it looks like you're pretty convinced of what you need to do. I will just comment on this :


> If it only was that simple i would jump at a 96V system...
> Going with a repurposed bike-motor and custom system for everything is nothing i would like to do since that would be a fully custom system with few or no replacement parts. The RPM would probably be quite high for powering a propeller...
> You can find 96V controllers/motors, if you check the links posted, rated up to ~40kW, if i remember correctly, for around $3000 complete with a controller and liquid-cooling.


That drivedrain primarily provides a source of a motor and and a motor controller. Since it can come from the secondary market, it would be potentially much cheaper than new factory equivalent. There is nothing super custom about it or about Sevcon gen4 controller. There is no point to use their vehicle control module or their battery pack, since you need a significantly bigger one. The motor is rated for 6000RPM, which is what their bikes will do. At 6000RPM they reach about 140kmh. Now I didn't catch if you wanted a direct drive at 1000RPM, but I have a suspicion it will be difficult to get the torque you desire at such low RPM, so you will end up with a reduction anyway. 6:1 is pretty straightforward in this case.


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## patric (Aug 1, 2021)

cricketo said:


> I am not going to dissect every line of your argument as it looks like you're pretty convinced of what you need to do. I will just comment on this :


I was just trying to show other considerations that needs to be included in this. I would prefer having a 96v system due to the reduced losses in the system, but switching to 96V would increase costs for other systems a lot more than the small saving you would get from using a second-hand motor. Just a new marine genset would run easily run $3k-$4k and replacing just the generator on one with something custom would probably run at least half that.

But i welcome all comments because if forces me to reconsider things.


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## brian_ (Feb 7, 2017)

cricketo said:


> The motor is rated for 6000RPM, which is what their bikes will do. At 6000RPM they reach about 140kmh. Now I didn't catch if you wanted a direct drive at 1000RPM, but I have a suspicion it will be difficult to get the torque you desire at such low RPM, so you will end up with a reduction anyway. 6:1 is pretty straightforward in this case.


Also, note that while the motor can go to 6,000 RPM, it doesn't need to for peak power, so a less extreme reduction ratio and lower motor speed can be used.


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## cricketo (Oct 4, 2018)

I don't understand how you got the genset mixed into the voltage question. Standard way of coupling power generators is via the inverters and the AC path.

The other thing I was thinking, is you could partition your battery bank into two. Have the two 48v parts connect in series for "traction" 96v use. Then also have two 48v AC inverters connect separately to each of the two, parallel and synchronize with each other on the AC side. That's also where your generator would plug in. 

Same way two charge controllers can sit on individual 48v parts, but parallel on the PV input side. So basically systems become coupled in such way that the two 48v batteries get loaded/charged equally whether the load is via 48v systems or via the 96v systems.


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## brian_ (Feb 7, 2017)

patric said:


> Some AC controllers do seem to support being put in parallel to provide a more Amps to the motor. Need to do some more research, but starting to think that multiple motors/controllers is the way to go if i'm unable to go above 48v.


Yes, but that gets really expensive. Using two small controllers instead of one larger one is likely to be more expensive, and is a last resort if a suitable single controller can't be found.


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## brian_ (Feb 7, 2017)

cricketo said:


> I don't understand how you got the genset mixed into the voltage question. Standard way of coupling power generators is via the inverters and the AC path.


Not likely. If you have diesel-electric drive without a battery, the genset directly powers the inverters (or even AC gensets directly power motors); vast numbers of locomotives, many large mining trucks, and many ships have been built that way. In a vehicle with a traction battery (including hybrid cars and ships), the battery floats at the DC bus voltage, with any gensets feeding that bus and all loads drawing from that bus - it's basically a non-battery DC system with a battery attached at the DC link. To be practical and functional, the genset output, other charging sources to support propulsion, the motor(s), and the battery all need to agree on voltage.

Even if you built some weird thing with separate power supplies from gensets and a battery, you wouldn't use separate motor controllers for the two sources, so the genset voltage would still need to be roughly similar to the battery voltage.


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## cricketo (Oct 4, 2018)

brian_ said:


> Not likely. If you have diesel-electric drive without a battery, the genset directly powers the inverters (or even AC gensets directly power motors); vast numbers of locomotives, many large mining trucks, and many ships have been built that way. In a vehicle with a traction battery (including hybrid cars and ships), the battery floats at the DC bus voltage, with any gensets feeding that bus and all loads drawing from that bus - it's basically a non-battery DC system with a battery attached at the DC link. To be practical and functional, the genset output, other charging sources to support propulsion, the motor(s), and the battery all need to agree on voltage.
> 
> Even if you built some weird thing with separate power supplies from gensets and a battery, you wouldn't use separate motor controllers for the two sources, so the genset voltage would still need to be roughly similar to the battery voltage.


That contradicts the design principle OP wants - mostly standard, off-shelf components. How many 35kW diesel-electric locomotives to steal the parts from are out there ? 

Edit: maybe Chevy Volt would qualify ? But the voltages are way higher than what he wants


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## brian_ (Feb 7, 2017)

cricketo said:


> That contradicts the design principle OP wants - mostly standard, off-shelf components. How many 35kW diesel-electric locomotives to steal the parts from are out there ?


I'm not suggesting a system running a hundred of volts, or weighing more than the boat. I'm saying that rationally all of the components - generator, battery, controller - would be at the same nominal voltage - that's typically 220 to 360 V in a hybrid car, and several hundred volts in a ship, but 48 volts is the preferred voltage in this case. If you're using something like a 120 VAC (or 230 V 50 Hz for patric in Sweden) genset in a project like this, you're on the wrong track. I assume that the plan is to use any one of the many units you can find if you do a web search for "48V DC marine generator"; some of them are even listed as being suitable for hybrid propulsion.



cricketo said:


> Edit: maybe Chevy Volt would qualify ? But the voltages are way higher than what he wants


Yes, the obvious way to get the parts for a plug-in hybrid vehicle is to salvage parts from a plug-in hybrid vehicle. No one produces a 48 V PHEV, so as long as that system voltage is desired, that salvage option is out.

As patric has already noted, the main type of component available as salvage for a ~48V system is battery modules. In addition to Tesla Model S/X (module pairs in series for 45 Vnom), there are some other 3S, 4S, 6S, and 12S modules which could be used in appropriate combinations.


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## patric (Aug 1, 2021)

cricketo said:


> I don't understand how you got the genset mixed into the voltage question. Standard way of coupling power generators is via the inverters and the AC path.


Because marine gensets are usually much lower voltages, at least on smaller boats, and refitting one for higher voltages would cost quite a bit more than any savings of using a repurposed motorcycle motor. I just took this as one item as an example for one of the more costly things a 96V system would require.
A new smaller marine genset usually would run you $4-5k. Repurposing a existing one probably closer to $2k



cricketo said:


> The other thing I was thinking, is you could partition your battery bank into two. Have the two 48v parts connect in series for "traction" 96v use. Then also have two 48v AC inverters connect separately to each of the two, parallel and synchronize with each other on the AC side. That's also where your generator would plug in.
> 
> Same way two charge controllers can sit on individual 48v parts, but parallel on the PV input side. So basically systems become coupled in such way that the two 48v batteries get loaded/charged equally whether the load is via 48v systems or via the 96v systems.



So if one inverter fails both would go offline. So for redundancy you would need at least 4 inverters instead of 2. $1200 * 4 = $4600
For DC-DC converters you would need at least 4 for every single voltage to have a semi-redundant system. [email protected] + [email protected] = 8 dc-dc inverters at a minimum.. Probably more like 12 to have dedicated ones for the critical systems. This is due to if one DC inverter fails you get a failed string so two of them falls out. 12 * ~$100 = $1200
For the MPPT chargers 2 chargers with 2 panels each. If one charger fails then both are unusuable. Need to keep at least one spare, but probably two. ~$250 each. 4x250 = $1000
+ Fuses, cables and all other extra stuff would be a few hundred
Not sure how you could monitor this in a sane way, but maybe you could just have two separate monitoring systems for each 48v part of the setup.. $500 each..

And where would you even start troubleshooting a system like this if any of the critical systems stops working while out at sea.. You cannot really pull over and call a towtruck. 

So we we sum it up for a 96V system:
96V system we have at least $7800 for a redundant power-distribution system. More like $9800 if we include re-purposing a existing genset for higher voltages. On top of this we have the cost of the 96V motor... Say $2500 for the 96V motor+mounting system = $12300

For a 48V system:
$7800/2=$3900 for a redundant power-distribution system. 

So before a 96V system would start to make sense would be if two 48V motors+controllers+mounting system would cost more than ~$8400

Going with two [email protected] controllers/motors ( ~$2500 each ) i used in a previously example, capable of up to 1200A (!!) peak, would still cost less than a complete 96V system while keeping complexity fairly low.

I recommend you to read my long post above, or at least skim thru it to get an idea of things you need to consider on a boat.


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## patric (Aug 1, 2021)

brian_ said:


> I'm not suggesting a system running a hundred of volts, or weighing more than the boat. I'm saying that rationally all of the components - generator, battery, controller - would be at the same nominal voltage - that's typically 220 to 360 V in a hybrid car, and several hundred volts in a ship, but 48 volts is the preferred voltage in this case. If you're using something like a 120 VAC (or 230 V 50 Hz for patric in Sweden) genset in a project like this, you're on the wrong track. I assume that the plan is to use any one of the many units you can find if you do a web search for "48V DC marine generator"; some of them are even listed as being suitable for hybrid propulsion.


A 45ft sailboat, or even a 45ft motor-trawler, do NOT run at several hundred volts. Common voltages on this size of boat are 12v/24v and the more modern ones with larger inverters, for using induction cookers/microwaves/etc, have started to move over to 48v systems in recent years.

To get to ships running hundreds of volts you have to look at much larger ships that have dedicated generator-rooms and such.

Most of the sailboats i'm considering do already have dedicated gensets, such as sound-proofed Fisher Panda's etc, and AGM banks @ 48v. Might need to bump up the RPM of the genset a few % to support a bank @ 57v max-charge, but that should not be a huge issue. Possibly getting a new charge controller for it, to control the charge currents, would also be doable at a fairly low cost.


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## cricketo (Oct 4, 2018)

No. If one inverter fails, you can still run the other one at the expense of having to rebalance your other loads to the other battery. Same goes for DC-DC converters. And even remaining solar charge controller can be flipped between the two batteries. If you are planning for this to be a semi-normal mode of operation, then some automation may be needed to make life easier, but ease of manual rewiring in case of the emergencies should be part of the design anyway.

I don't know what you mean by two separate monitoring systems. You will need a BMS for your battery for balancing and individual cell monitoring, and independently can have a couple of coulomb meters on each part of the battery if you need to rebalance the loads. The degree of sophistication like I suggested earlier depends on the your expectation of reliability. It's nice to have redundancy, but then you're not bringing a second sail boat with you. Some components makes sense to duplicate, some it doesn't.

One more time on your 600A expectation. Here is the manual for for Curtis motor controllers :


http://www.thunderstruck-ev.com/Manuals/1234_36_38%20Manual%20Rev%20Feb%2009.pdf


These are industrial grade motor controllers. I have 1236se in my 12,000lb (5400kg) boom lift. Last page lists the limits on them, so for instance 1238-56XX (48v) series is advertised as a 650A controller, but according to the specs 650A is only for 2 minutes, while continuous operation is capped at 210A. The point of supporting those peaks is to allow for inductive loads to start, which often requires more amps. In your case though, continuous operation is necessary. Now, even the footnote makes some suggestions regarding heatsinks, so it may be possible to get the controller going at its max longer, but I find it strange that you'd go to extreme with redundancies in other parts of the system, while leaving a major weak link in form of a motor controller that's pushed to its limits under normal conditions.


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## brian_ (Feb 7, 2017)

patric said:


> Still researching solar-panels and how they could be setup, but 4x400W panels on the back arch + 2x400W that are manually moved around when at anchor. 4 panels @ 45V = 180V so on the edge if going with a 168V battery-pack.
> 144v and below should be doable either way, but still hard to source components. Possibly finding a _good_ MPPT charger with boost functionality, have so far only found crap Chinese versions with contradicting specifications.


Boosting MPPT solar charge controllers may exist, but I don't think they're common. MPPT controllers are normally only buck converters, which supports the approach of keeping the battery voltage down to make solar array configuration more practical.



cricketo said:


> I would add that for PV systems the open circuit voltage shouldn't be targeting the battery pack voltage directly, but rather the charge controller's operational input voltage. Then, charge controller should be the one also be matched to the battery pack on the output side.


Yes, with an MPPT controller the PV array voltage must exceed the fully charged battery voltage but can be much higher than that, as long as the open circuit voltage does not exceed the controller's input voltage range. On the other hand, with a small array in a small space I don't see any advantage of going high in array voltage... and patric has explained the advantages of avoiding long strings of cells.

On the controller output side, what needs to be matched is current capacity, rather than voltage (assuming that the input voltage is higher than the battery voltage by an adequate margin): the controllers need to handle the current required at the battery voltage to transfer the power output of the array.


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## brian_ (Feb 7, 2017)

patric said:


> A 45ft sailboat, or even a 45ft motor-trawler, do NOT run at several hundred volts.


I had used examples of much larger systems, and cricketo was acting as if I was suggesting the voltages of those systems for a yacht - I was never suggesting that, just explaining why the generator output is DC at the battery voltage (whatever that is in the particular vessel).

On the other hand, while the general electrical systems of yachts and even the propulsion systems of low-power low-speed boats are not that high, higher-power yachts do use the higher voltage which makes sense at their power level. Torqeedo is up to 360 volts (using BMW i3 and i8 complete battery packs), not just in their big systems but even in a 25 kW saildrive.

What is driving the 48 volt selection for this project is wanting to have a common voltage for propulsion and other loads, mostly to minimize complexity, and that makes sense to me at a low power level. It appears that the goal is the functionality of something like this Torqeedo system

.... but without as much complexity by reducing the number of voltage conversions.


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## brian_ (Feb 7, 2017)

I ran across the Solarwave 62 while looking for hybrid yacht examples... and it turns out to use a 48 V system with 22 kW propulsion motors. The whole Silent Yachts line looks interesting...


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## patric (Aug 1, 2021)

cricketo said:


> No. If one inverter fails, you can still run the other one at the expense of having to rebalance your other loads to the other battery. Same goes for DC-DC converters. And even remaining solar charge controller can be flipped between the two batteries. If you are planning for this to be a semi-normal mode of operation, then some automation may be needed to make life easier, but ease of manual rewiring in case of the emergencies should be part of the design anyway.


This is probably nothing you want to do with a batterypack with a price-tag of $14000 ... Just consider what the BMS will do in case of such an imbalance or what the load on the batteries will look like if you use the engine when there is an imbalance.

Solarpanels on a boat will fluctuate quite a lot, due to shadows from the masts etc, so you cannot compare this to a normal house-roof system. Any automation for moving these between the two legs would add quite a bit to the cost and complexity.



cricketo said:


> I don't know what you mean by two separate monitoring systems. You will need a BMS for your battery for balancing and individual cell monitoring, and independently can have a couple of coulomb meters on each part of the battery if you need to rebalance the loads. The degree of sophistication like I suggested earlier depends on the your expectation of reliability.


Have a look at for example the Victron Energy equipment that allows for multiple MPPT chargers to work together to charge the batteries and a display that shows the current status. Would it even be possible to network them together between different legs? If they share a common positive terminal somewhere you would have huge issues if doing a 48+48 split.



cricketo said:


> It's nice to have redundancy, but then you're not bringing a second sail boat with you. Some components makes sense to duplicate, some it doesn't.


No, but you bring plugs to be able to quickly plug a broken thru-hull where water is rushing in.. You bring a form of putty that you can use to plug quite large holes/gashes.. You bring diving equipment in case you need to fix the propeller.. You have multiple bilge-pumps that can pump out huge amounts of water in case of a leak or rouge wave getting into the cabin... And you spend around 5-10% of the vessels value per year, on average, in maintenance of the hull/rigging/motors/electrical systems..
You do not want to increase the number of possible failure points on the most CRITICAL systems.. Guess why most bilge pumps are wired directly to the batteries and controlled by a float-switch?

You have no clue what you are talking about in this manner. I would suggest you to stop trying to apply your EV car knowledge to the safety requirements in the marine world because they are worlds apart.
Critical systems must have enough redundancy to cover the most common faults, such as a failed DC-DC converter, cause there are many instances when you are unable to enter the engine-room to try and rewire to get primary systems back up.

Failure of navigation lights, propulsion and radio at nigh in a crowded channel can go REALLY bad REALLY quickly, and you will probably not have time to go down to rewire stuff to get it running again. Failure of just the navigation-lights can be mitigated by radio communication and reporting GPS location. A active AIS would even allow other boats to see you electronically.
Or lets say you loose all of the primary systems in rough weather.. No engine, no radio, no navigation lights, no GPS, no AIS, no chart-plotter. Going in to troubleshoot/rewire a complex 96v/48+48v system in rough seas is nothing i would recommend.

This is why there needs to be quite a bit of redundancy in the electrical systems so any single failure does not take out multiple primary systems.



cricketo said:


> One more time on your 600A expectation. Here is the manual for for Curtis motor controllers :
> 
> 
> http://www.thunderstruck-ev.com/Manuals/1234_36_38%20Manual%20Rev%20Feb%2009.pdf
> ...


I have not stated any requirement of using a single controller to power a 48V motor @25kW. One of my initial questions was related to what options was out there and also the possibility to have multiple controllers powering a single [email protected] motor. The Curtis controllers i linked to even had the option of a water-cooled chill-plate. I even wrote about using two 48V motors on the same 

So if we take the most extreme setup from my previous comments/questions that would be 2 controllers per motor and 2 motors. Ie 25kW over 4 controllers and 2 motors.. Or [email protected] per motor and [email protected] per controller. If one controller fails there would still be three functioning ones and if a motor fails there would still be a secondary motor providing half of the normal power.
Keeping a spare controller or two (for the ones i linked to) would add a few hundred to the total cost. 

If you also read what i wrote regarding engine-power where i stated that engine power is not critical on a sailboat since you still have sails you can use to get to a safe place to drop anchor. I would say navigation-lights are of a much higher priority, at night, over having a working engine on a sailboat.
Main usage for a motor on a sailboat are:

Motor when there is no or little wind, but this is nothing required... You can still wait on the boat until the wind comes back.
Possibility to motor-sail in low-wind conditions to reach a better location with higher wind-speeds. Also nothing required.
Motor thru canals where sailing is not possible or allowed. Panama canal for example require a minimum speed of 5knt and that would be required for a few of hours. Doable @15kW or so.
Motor in and out of marinas.. And worst case you can always wait for calmer seas if it would put too much demand on the engine.
Motor to make it easier to set an anchor... 5-10 minutes at really slow speeds.
Have as a security to be able to make quick movements in case of another boat dragging anchor and risks a collision with you. Possibly up to max power for 30 seconds or so.
Gives better control of the boat when giving assistance to someone else. Much better control when matching speeds etc...
Regen-charging of the batteries in case there is no or little sun... Or you go with a drag-able generator you have on a line after the boat.

And as you can see basically none of those presents a huge risk.. A slow collision at anchor would at most cause some superficial, but possibly costly, damage.

Your redundancy for the motor on a sailboat are the sails.
Your redundancy for the sails on a sailboat is the motor. Only time it would become impossible rig up new sails is if the boat gets dis-masted, and that should be extremely rare on a well-maintained sailboat.
Your redundancy for the electric autopilot is a windwane..
Your redundancy for the electric bilge pump are a few more electric bilge pumps, fused & powered seperatly, plus a manual bilge pump..
Your redundancy for the radio is the AIS, navigation lights and possibly the fog-horn.
Your redundancy for the AIS is your radio, navigation lights ad possibly the fog-horn.
Your redundancy for the navigation lights is the radio, AIS and possibly the fog-horn.
Your redundancy for the radar and depth sounder is your AIS and chart-plotter (or possibly paper-charts) 
Your redundancy for the fog-horn is the navigation-lights, AIS and radio.
Your redundancy for solar is regen-charging when sailing
Your redundancy for regen-charing is solar..
Your redundancy for solar & regen is the generator.
Your redundancy for the generator is the solar & regen..

The most important systems are the ones that can notify others of where you are or how you can stay away from others (AIS, radar, navigation-lights, fog-horn, radio) . Usually you try and get all of these systems at the same voltage as the battery bank to remove as many single points of failure as possible, or possibly have dedicated DC-DC converters between the battery and each individual device or a parallel setup where multiple DC-DC converters would have to fail at the same time to bring down all of those systems.
Having a DC-DC converter go bad is quite common...

When you only read part of the descriptions, and assume a bunch of things, you fail to realize why some choices are made. There are some regulations all boats must follow and some extra regulations when going above 50V.


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## patric (Aug 1, 2021)

brian_ said:


> I ran across the Solarwave 62 while looking for hybrid yacht examples... and it turns out to use a 48 V system with 22 kW propulsion motors. The whole Silent Yachts line looks interesting...


Have been eyeing them for inspiration a bit.. They do have the benefit of being a catamaran where they can have two engines, but their engines are quite nice, but also quite costly as anything marketed for the marine market...
A few more places with motors targeted for the "marine" market, that i have looked at:


https://electricyacht.com/electric-sailboat-motors/






__





Oceanvolt - Electric Propulsion Systems for Monohull


Oceanvolt offers clean electric power & propulsion systems in partnership with many leading monohull boat builders - adding new partners continuously.




oceanvolt.com








__





Electric Inboard Motors - Elco Motor Yachts


Click on an inboard to see more options.




www.elcomotoryachts.com





and a mix of a few more here:








Electric Inboard Boat Motors - Plugboats


Plugboats Guides Motors News Motors For Sale With information about 150 electric inboard boat motors from 17 manufacturers, welcome to




plugboats.com




but do keep in mind that some of these motors have just had a logo with a marine-brand slapped on them to be able to bump up the price..


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## Aquasylum (Oct 26, 2020)

We converted a Silverton 34' Motoryacht to electric drive this spring. Thunderstruck Motors sold us a pair of controllers (already programmed) and Motenergy 10Kw motors. Boat is ready to go "at the flip of a switch" and she is super quiet. We are still doing sea trials on range/consumption. 2 x 48v lead acid battery banks (4 x 12v 150 Ah batteries), we don't have much run time now. Weight was not a consideration as the gas burning engines were ~1,000lb each. 

The hardest part of the installation: building a 4:1 reduction gear on a motor plate that incorporated thrust bearings to handle the axial thrust from the propeller. We used Baldor Dodge gears. Machining the 1/2: stainless steel plates required a large commercial pillar drill and a lot of expensive bits + 2 bottles of fine scotch for the machinist. We wanted 500 rpm at the props with the motors running at 2,000 RPM. Thunderstruck has a 2:1 reduction gear and was a big help, but the 4:1 was something we had to design and build ourselves. Not for the faint of heart!

You can see her under way here and the below-decks operation during a 180' turn here.

Version 2.0 will be to add a Yanmar diesel and 2 60 or 80 amp 48v alternators, she'll be a "true hybrid." We can cruse at 5-6 MPH at 60-80 amps (we will measure precisely once the instrumentation is hooked up later this month). 
Version 3.0 will be in 5 years at battery end-of-life: We'll put in 300+ HP Tesla motors and 2026 battery technology (at least 100Kw/bank), boat will go up on plane again at 18-20 knots but will be silent except for the whoosh of the water.


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## brian_ (Feb 7, 2017)

I assume that most of the electric yacht stuff is unreasonably expensive, due to the market.

The Electric Yacht motors look like various Motenergy models.
It's not clear how many - if any - of these companies make their own motors; it probably wouldn't make sense for any of them to do it.
A lack of detailed technical information is common.
The Plugboats list certainly shows the tendency to low voltages, although some are up to a few hundred volts.
The length of the list is impressive.


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## brian_ (Feb 7, 2017)

Aquasylum said:


> We converted a Silverton 34' Motoryacht to electric drive this spring.


This is the discussion in this forum:
*34' Silverton Motor Yacht, now Electric Boat!*


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## Frank (Dec 6, 2008)

I don't have time to read the whole post at this point but my quick comments are:

- my father-in-law's boat (48' cold molded) runs on 144 V and draws about 80A during cruise. It's especially efficient when motor sailing (fixed prop works best!)

- I just saw another (smaller) project (maybe 30' day sailer) that used a 48V system. Looking closely at the motor revealed it was a Motoenergy (I can't remember the model). There are commercially available systems out there for inspiration. Both the above are sail drives BTW...


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## patric (Aug 1, 2021)

Aquasylum said:


> We converted a Silverton 34' Motoryacht to electric drive this spring. Thunderstruck Motors sold us a pair of controllers (already programmed) and Motenergy 10Kw motors.


Looking and sneaky good! 

Anything you would have done different in regards to the motors if you where to do it again with the knowledge you have gained?


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## patric (Aug 1, 2021)

Frank said:


> - my father-in-law's boat (48' cold molded) runs on 144 V and draws about 80A during cruise. It's especially efficient when motor sailing (fixed prop works best!)


Good data-point.. So [email protected] ~11.5kW.. Have been counting on around 15kW at cruising speed for a 45' steel-hull so math seems match up fairly ok. His would probably be half the weight of a 45' steel hull but after getting up to speed the resistance in water should be fairly similar.

Any numbers on what draw he has seen in different sea-states?

For prop i will have to consider efficiency of regen / motoring / cost and find some good middle-ground. Motor-sailing is far down the list for me, at least for now, and props with tiltable blades might just get too expensive for the small gain.


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## Frank (Dec 6, 2008)

I'm not sure how much his boat weighs, half seems low, she's a well-built cruising vessel. Another friend built a 50' steel boat and he thinks she displaces about 48,000# but says he's never had a good Travellift readout. There's a lot of variation depending on plate thickness, etc. and how she'll be outfitted.

Not sure about draw for various sea states but the in-laws boat has crossed the Atlantic and back. I know the generator is 19 kW and everyone thought replacing a 70 HP Westerbeke with a smaller electric drive system wouldn't work but it seems to work fine. They carry a lot of fuel and my FIL figures it's tripled his range when motor sailing.

A prior iteration had two (smaller) dedicated generators driving motors directly (with no batteries) but that system seemed to be cobbled together by a couple of designers who'd never sailed. It only lasted a few years and was nothing but trouble. You definitely want battery-electric where everything is easily understandable, multiple ways to charge, etc.


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