Sailboat conversion from 14 hp Diesel to 10 Kw 48V electric motor

keimor85

New Member
Looking good. In a stiff wind will it regen your batteries?
Possibly a bit when I get over 6 kts. My hull speed is 6.4 kts and there is almost always a stiff breeze in Nantucket Sound so I'm at hull speed often. We will see and I'll report after some time sailing. I will hopefully launch in early May.
 

jwelter99

Solar Addict
Here is the latest update on my conversion. The motor is installed. I had to extend the stringers and shorten the prop shaft but all of that went well. I changed my plans on 12V power I already had three 12V 79Ah group 24 AGM batteries so I bought a new 12V 79Ah group 24 AGM and wired them in series to give me 48V. The 48V is wired to a switch and then to the 10Kw 48V motor. I then wired the 48V to 12V DC to DC converter directly to the 12V panel. Through the converter the panel is constantly at 13.9V.

The motor and prop are spinning although only for a few seconds at a time since I'm on the hard and no water is in the cutlass bearing. Solar panels are wired in and charging. I'm installing a new 12V electrical panel as well. The old one was working fine but at 41 years old I figured it was time. At this point I'm waiting on the LiFePO4 cells from China, they are not late yet and should be here in the next few weeks. I should have ordered them sooner. Once the cells arrive from China and are balanced and the battery box is built I will install another switch and wire the LiFePO4 battery to the motor. The LiFePO4 battery will only be used for the motor. The AGM battery bank will be primarily used to power the 12V panel but with the flip of a switch it can power the motor in an emergency. With only 79Ah and about 50 of them usable it won't take me to far but again it's for an emergency. The last pic shows the mockup of where the LiFePO4 battery and BMS will be located.

View attachment 44891

Nice clean install.

One thing we see done quite often on such propulsion conversions is using a BMS that is not common port (uses FET for the power disconnect) design.

The reason is that on motor start you can see very high current loads for very short periods that are well over 1C rate, particularly on smaller battery banks. A use case might be while docking where you can have multiple fwd/off/rev cycles in a short period.

These sorts of loads will kill the FET's in the BMS fairly quickly in a common port design. Ideally you should be running a BMS that uses an external contactor for control. The contactor(s) can be sized to handle these surge loads. You also should carry a spare as can be replaced at sea if needed.

I believe your setup already has a contactor in place on the right side of the motor mount. It is also possible to have the BMS and motor controller share control of this contactor to further simplify the system.
 

Tuttifrutti

Solar Enthusiast
Yes I had meant to post a reply to your thread but ran out of time this morning and this one came up in my search. As far as I know, you can't charge the two completely different (different voltage, maybe different chemistry) battery banks with one charge controller. Well, one charge controller can do the three things you listed, one at a time. It would need to be rewired and reprogrammed to switch between them.

Using a 48V/12V converter would probably work most the time because if its voltage is at least 13V, it is acting like a trickle charger, keeping the 12V battery topped up and providing power to the 12V system. It there's a problem with the 48V battery or converter and the 12V battery gets drawn down, the 13V when it's available again may be too low to effectively recharge the 12V battery. But maybe the 12V battery's capacity was enough to get through the emergency and it could be charged off board or with a portable charger. Or, maybe you'd be away from port and have the time to rewire and repogram the MPPT to charge the 12V battery with the solar panels.

No problem! I definitely see the issue here. I guess the best solution would be to keep the conversions and charging simple.

Ref this thread: https://forum.solar-electric.com/discussion/16052/charging-a-12v-bank-from-a-48v-bank

Quote: "The Morningstar 15 Amp MPPT will be set-and-forget. When it sees the 12 Volt battery is fully charged it will cut back to Float Voltage and stay there. It will also handle the down converting of 48 Volts to 12 Volts fine. Its maximum input Voltage is 75, so not even an equalization charge on the 48 Volt bank will be a problem."


If I understand this correctly, its possible to use the MPPT as a charger/converter from 48v to 12v with float voltage, and from solar panels to 48v to 12v?
 

SV_Stray_Cats

Solar Enthusiast
If I understand this correctly, its possible to use the MPPT as a charger/converter from 48v to 12v with float voltage, and from solar panels to 48v to 12v?
Yes, charging a DC battery with DC power input is exactly what solar charge controllers do, and they must be the most common DC charging application, so we have plenty to choose from, with history and reviews. The charge controller wouldn't care or know whether the 48V comes from a PV panel or a battery. But I wouldn't pay extra for MPPT for this application. That's Maximum Power Point Tracking and is a feature that takes advantage of PV panels being constant current devices; the charge controller varies the panel voltage to find the max power output in varying light conditions.
 

keimor85

New Member
Nice clean install.

One thing we see done quite often on such propulsion conversions is using a BMS that is not common port (uses FET for the power disconnect) design.

The reason is that on motor start you can see very high current loads for very short periods that are well over 1C rate, particularly on smaller battery banks. A use case might be while docking where you can have multiple fwd/off/rev cycles in a short period.

These sorts of loads will kill the FET's in the BMS fairly quickly in a common port design. Ideally you should be running a BMS that uses an external contactor for control. The contactor(s) can be sized to handle these surge loads. You also should carry a spare as can be replaced at sea if needed.

I believe your setup already has a contactor in place on the right side of the motor mount. It is also possible to have the BMS and motor controller share control of this contactor to further simplify the system.
Are you suggesting to carry an extra contractor or an extra BMS?
 

Tuttifrutti

Solar Enthusiast
Yes, charging a DC battery with DC power input is exactly what solar charge controllers do, and they must be the most common DC charging application, so we have plenty to choose from, with history and reviews. The charge controller wouldn't care or know whether the 48V comes from a PV panel or a battery. But I wouldn't pay extra for MPPT for this application. That's Maximum Power Point Tracking and is a feature that takes advantage of PV panels being constant current devices; the charge controller varies the panel voltage to find the max power output in varying light conditions.

Ok, sounds good. Since I want to at least have the possibility to add solar panels, it makes sense to use an MPPT as a DC-converter from 48v to 12v and connect solar panels at a later stage. Then there's the question of having a separate 12V battery or not...
 

jwelter99

Solar Addict
Are you suggesting to carry an extra contractor or an extra BMS?

If you are on a common port BMS like the Daly it will fail. The FET's will not survive running a high current motor. You can carry a spare but that will fail as well. This is why things like FET based battery protects also do not work well on high current motors or inverters.

Or you can spend the spare money on buying a contactor based BMS and a good quality contactor. As mentioned it does appear your motor setup might have a suitable contactor you can do double duty with and use as the BMS disconnect so you don't need another in the system.

Do you have a schematic of the motor circuits?
 

keimor85

New Member
If you are on a common port BMS like the Daly it will fail. The FET's will not survive running a high current motor. You can carry a spare but that will fail as well. This is why things like FET based battery protects also do not work well on high current motors or inverters.

Or you can spend the spare money on buying a contactor based BMS and a good quality contactor. As mentioned it does appear your motor setup might have a suitable contactor you can do double duty with and use as the BMS disconnect so you don't need another in the system.

Do you have a schematic of the motor circuits?
OK now I'm confused. In your earlier post you said

"One thing we see done quite often on such propulsion conversions is using a BMS that is not common port (uses FET for the power disconnect) design."

In this quote you say that a not common port uses FET's. Then above you are saying that a common port uses FET's and they will fail.

So simple question do common port and non common port BMS both have FET's? Or was one of these statements a typo?

What type of BMS do you recommend for a high current application like mine that utilized a contractor?

What type of BMS is the prepackaged LiFePO4 batteries like Battleborn?
 

keimor85

New Member
OK now I'm confused. In your earlier post you said

"One thing we see done quite often on such propulsion conversions is using a BMS that is not common port (uses FET for the power disconnect) design."

In this quote you say that a not common port uses FET's. Then above you are saying that a common port uses FET's and they will fail.

So simple question do common port and non common port BMS both have FET's? Or was one of these statements a typo?

What type of BMS do you recommend for a high current application like mine that utilized a contractor?

What type of BMS is the prepackaged LiFePO4 batteries like Battleborn?
Here is a basic wiring diagram. Probably not enough detail. Please let me know and I'll get more from the supplier.
 

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jwelter99

Solar Addict
OK now I'm confused. In your earlier post you said

"One thing we see done quite often on such propulsion conversions is using a BMS that is not common port (uses FET for the power disconnect) design."

In this quote you say that a not common port uses FET's. Then above you are saying that a common port uses FET's and they will fail.

So simple question do common port and non common port BMS both have FET's? Or was one of these statements a typo?

What type of BMS do you recommend for a high current application like mine that utilized a contractor?

What type of BMS is the prepackaged LiFePO4 batteries like Battleborn?

Sorry, you interpreted what I wrote not as I intended.

Using common port BMS (which use FET's as the switching device) is not a good solution for high power electric motors as they tend to fail quite quickly. Most BMS manufactures specifically state they are not suitable for high current motors.

This then leads you to a BMS that uses contractor(s) for control. These usually have the contactor external to the BMS so you can use readily available high power contactors, and easily replace them. In these systems the main power does not flow via the BMS, but the BMS controls the contactor which enables/disables that flow.

Batrium, REC, and several others work this way. For a 12V marine pack like yours I would do a REC Active as it's easy and reliable but a bit higher priced than the China sourced units.
 

jwelter99

Solar Addict
Here is a basic wiring diagram. Probably not enough detail. Please let me know and I'll get more from the supplier.

That works, the LEV200 is the contactor and one that is broadly used in the marine community, for both disconnects like in your motor system as well as for BMS applications.

I am very certain that the BMS can share control of that contactor so you get a simplified system. The hookup depends on which BMS you use.

 

keimor85

New Member
Sorry, you interpreted what I wrote not as I intended.

Using common port BMS (which use FET's as the switching device) is not a good solution for high power electric motors as they tend to fail quite quickly. Most BMS manufactures specifically state they are not suitable for high current motors.

This then leads you to a BMS that uses contractor(s) for control. These usually have the contactor external to the BMS so you can use readily available high power contactors, and easily replace them. In these systems the main power does not flow via the BMS, but the BMS controls the contactor which enables/disables that flow.

Batrium, REC, and several others work this way. For a 12V marine pack like yours I would do a REC Active as it's easy and reliable but a bit higher priced than the China sourced units.
Thanks for the quick response. I have a 48V 16S 3.2V 202Ah pack not a 12V. Is the Batrium, REC still the answer?
 

jwelter99

Solar Addict
Thanks for the quick response. I have a 48V 16S 3.2V 202Ah pack not a 12V. Is the Batrium, REC still the answer?

Batrium yes but REC I don't like their >4S units as they have a habit of cooking their balance resistors.

With 48V it is a bit more limited selection. Let me ask one of the electric conversion gurus at work tomorrow what's a reasonable 48V BMS for such an application.
 

keimor85

New Member
Batrium yes but REC I don't like their >4S units as they have a habit of cooking their balance resistors.

With 48V it is a bit more limited selection. Let me ask one of the electric conversion gurus at work tomorrow what's a reasonable 48V BMS for such an application.
Fantastic, thanks for the help
 

jwelter99

Solar Addict
J,

Any info on the BMS that I should use on my application?

Sorry!

Two recommendations:

Orion Jr 2 BMS will do up to 16 cells.
Rec Q BMS will do up to 16 cells.

Both are good reliable products, but the Orion was better recommended. Some issues in the past with the balance resistors in the REC burning up but supposedly that has been solved.
 

keimor85

New Member
Sorry!

Two recommendations:

Orion Jr 2 BMS will do up to 16 cells.
Rec Q BMS will do up to 16 cells.

Both are good reliable products, but the Orion was better recommended. Some issues in the past with the balance resistors in the REC burning up but supposedly that has been solved.
Thank you I'll look into them
 

keimor85

New Member
I launched on May 5th with just 4 79Ah group 24 AGM batteries in series to provide 48 V. I already had three that were new last year so rather then delay my launch waiting for the 3.2V cells to arrive from China I bought the 4th battery. I waited to long to order my 3.2 cells from china. I was nervous with only 79Ah and being AGM's only about 45 Ah usable. As it turns out the AGM's actually work just fine for my use which is motoring 1/2 mile in and out of my harbor. I was even able to motor a few miles as well. This is how ever like running your car with just a few gallons in the tank and was a bit nerve racking especially when one day I had to motor into a 30 Knot wind which really sucks up the Ah.

The cells arrived mid may and I charged them up in 4 groups of 4 to 3.5V then put them in parallel and top end balanced to 3.65 and describe by Will. While I was charging the batteries I designed and constructed the battery box and platform. As mentioned on this site cell movement is a critical issue so I designed pressure plates with jack screws to load the batteries in the X and Y direction. see pics below. The box was epoxied, screwed and then glassed on the edges. My speed vs Amps has exceeded the manufactures estimates for my boat/hull design. Which means my range expectations have also been exceeded. The torque of the electric motor is incredible vs the diesel.

I went with 4 70W solar panels and a Victron 48V controller 110V/20A. Unfortunately the solar panel are exceeding the manufactures specs (I hate it when that happens :) ) and at max V are seeing 118V which faults out the controller so I had to use just three panels. The three panels have brought the batteries to full charge every day with the most Ah produced/replaced being 22Ah. The only problem with the solar panels is shading form the boom when on morning. So I have to move the boom to port or starboard when I leave the boat and depending on if the weather service was correct or not with there wind direction prediction I may not get max production out of the panels. I may get two more panels to ad to the one that I already have and another controller and set the two arrays up as port and starboard that way at least one will always be producing to the max and I won't have to worry about the weather service accuracy and moving the boom around.

Jwelter 99 - I am using the Dailey BMS and so far it is working fine but I have it designed so if/when if fails I can jumper around it until I get a new Orion or rec BMS. I also can just flip the switch and use the AGM batteries.

I am ecstatic about this conversion it has exceeded my expectations in so many ways.
Box epoxied and screwed together.JPGbox edges glassed.JPGBMS wiring complete.jpgjack screws epoxied in.JPGLiFePO4 Battery complete.jpgSolar panels on dodger.jpgSpeed vs Amps.pngMOONDANCE.jpg
 

keimor85

New Member
Possibly a bit when I get over 6 kts. My hull speed is 6.4 kts and there is almost always a stiff breeze in Nantucket Sound so I'm at hull speed often. We will see and I'll report after some time sailing. I will hopefully launch in early May.
Bubba thanks for the thumbs up. As far as regeneration I do get it in spurts but it is not enough to offset the amps needed to keep the contractor closed. I have a 2 bladed prop maybe with a 3 bladed prop it would work but I think that you really need a bigger boat with higher hull speed but then you would have a higher Kw motor so I'm not sure.
 
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