Two electric unicycles + 140kWh of dead cells + Solar panels (Bayliner hybrid)

[HOTOREL]

With such a low power requirement, why don't power everything in 48V?
That will be way more easy and reliable.

The thing is that for 48V 4kW is the maximum motor size powervise that you can install. In my case, I’m using this motor just because I already have it and it will help to do all the tests and collect enough data. The thing is that I don’t know anyone who would retrofit the power yacht of this type with electric power yet. So to build something you have to do some research. Plus using 100.8V (I don’t know why I mentioned 96V before…) allows me to scale up my system easily. There are so many cheap options up to 15kW which would be more than enough but again, we will see everything pretty soon. Because right now I already working on the battery for the tests

 

[HOTOREL]

High dc voltage and salt water ?
The whole concept absolutely TERRIFIES me.
Two not insignificant dangers, electrolytic corrosion and electrocution.

Life is a dangerous thing. If you want to achieve something big - you should go out of your comfort zone.
And use technology to make everything safe

Edit:
P.S. I already have 130V DC from my solar panels and will have more than 200V when I finish my setup

 

[HOTOREL]

This is AWESOME please keep us informed!! Once my RV remodel is finished and we're bored of exploring the land I'm planning on getting an electric yacht or building my own.

https://www.silent-yachts.com/silent60/

Thanks for your kind words. More to come soon. Silent 60 is amazing but to unreal for us now. But we will see that will be in the future. Technoloy is already here so it is time to do something cool with it)

 

[yabert]

The thing is that for 48V 4kW is the maximum motor size powervise that you can install.... There are so many cheap options up to 15kW

Yes, I understand. I'm also looking at a motor solution for a big sail boat and it's hard to stay at 48V if the need is 10-15kW continuous.
I would like to find a big 48V hub motor who turn less than 1000 rpm and output around 100 Nm continuous, but this is non existent.

About voltage, with 12S Leaf cells that give you around 45V nominal, so 90V total. Voltage range 72-100V
About your battery, can I suggest you a simple and reliable solution? Instead of building 24 batteries/24 BMS, please do you a favor and build 2 batteries with 2 BMS.
Based on 41Ah cells and 432 modules, you can connect 36 modules together to create one big 7.5V and 1476Ah modules. Then, connect 6 modules in series to create one 45V 1476Ah battery (12S and 66.4kWh).
Do this 2 time and add a simple 12S relay BMS to each battery.

And by the way, do your search, but Leaf cells have terrible degradation and many problem. So I suggest you to take your time and put your hands on better cells. There is plenty of EV at scrap yard and you will end to find something at good price for large battery (60-100 kWh).

 

[Warpspeed]

Life is a dangerous thing. If you want to achieve something big - you should go out of your comfort zone.
And use technology to make everything safe

Edit:
P.S. I already have 130V DC from my solar panels and will have more than 200V when I finish my setup

I will tell you a true story.

Many years ago when I was still a young fella, I helped launch a small aluminium power boat from a sandy beach into salt water.
I was in the water up to my thighs (with wet hands) when I accidentally contacted 12 volts from the top of the exposed on board battery.
I received a hell of a belt, and I will never forget it.

These days I have a solar system with a 100 volt battery (thirty lithium cells) and regularly come into full contact with that, and never feel even a slight tingle.
I guess us old farts tend to have have very dry skin.

So laugh at me if you like, call me a wimp, a coward, or totally crazy.
But I am a retired power electronics engineer, very used to working around dangerous high voltages as part of my job.
That is not a problem, because I know where the dangerous voltages are. Electrocutions always come completely unexpected.


The idea of working and maintaining a system with 350 volts of dc in a salt water boat just scares the shit out of me.
I have no problems working with 350 volts dc on an EV or solar system in a dry environment.
Salt and damp changes everything.

 

[Hedges]

Consider two 48V battery banks wired in series. Place a bypass diode across each (reverse polarity diode, sized and heatsinked to carry 100% of current.) That should protect their BMS from over-voltage if they disconnect.
That gives you 96VDC.

Alternatively, parallel multiple 48V batteries. Connect three European 230V inverters as 3-phase. Feed output to VFD to power motor.

3x Sunny Island would be 18kW.
I think SolArk (check out Deye for 230V model) being 120/240V split-phase and supporting 120/208Y as well, could probably be wired for 240V to neutral.

Other inverters should work - to feed a VFD.
If you had 360V or so battery, that could feed VFD directly. I don't think you can get away with stacking 48V batteries that high, due to voltage rating of EMI components.

 

[HOTOREL]

Yes, I understand. I'm also looking at a motor solution for a big sail boat and it's hard to stay at 48V if the need is 10-15kW continuous.
I would like to find a big 48V hub motor who turn less than 1000 rpm and output around 100 Nm continuous, but this is non existent.

About voltage, with 12S Leaf cells that give you around 45V nominal, so 90V total. Voltage range 72-100V
About your battery, can I suggest you a simple and reliable solution? Instead of building 24 batteries/24 BMS, please do you a favor and build 2 batteries with 2 BMS.
Based on 41Ah cells and 432 modules, you can connect 36 modules together to create one big 7.5V and 1476Ah modules. Then, connect 6 modules in series to create one 45V 1476Ah battery (12S and 66.4kWh).
Do this 2 time and add a simple 12S relay BMS to each battery.

And by the way, do your search, but Leaf cells have terrible degradation and many problem. So I suggest you to take your time and put your hands on better cells. There is plenty of EV at scrap yard and you will end to find something at good price for large battery (60-100 kWh).

You should check their website https://www.qsmotor.com/ I know at least a couple of motors with your requirements. And this is exactly why I am going with my motor from EUC (Electric Unicycle) because they have relatively low RPM (800-900 RPM max) and a lot of torque. The motor I have should provide more than 200Nm of torque. But again, we will see how it is going to all work together pretty soon.

Thank you also for your idea, but using only one BMS for the big battery has a lot of drawbacks. First of all, it is not ideal for BMS because it won't be able to manage each cell individually and this is exactly why you want to use BMS. If you have more than 2 cells connected in parallel in your battery pack it is already not good. In my case (when I have 24 BMS) I already have 4 cells connected in parallel so reducing the number of balancing wires will just make me throw my battery away as soon as a couple of cells are destroyed somewhere in the middle of this chain and I won’t be able to track them down at all. Plus when you have a lot of battery modules with each individual BMS you can lose or maintain some of the modules and still have power, while when you have only two batteries every error will leave you without power at all

And yes, I agree with you. If I will be able to find the better deal I will go with it but for now I don’t see any

 

[HOTOREL]

I will tell you a true story.

Many years ago when I was still a young fella, I helped launch a small aluminium power boat from a sandy beach into salt water.
I was in the water up to my thighs (with wet hands) when I accidentally contacted 12 volts from the top of the exposed on board battery.
I received a hell of a belt, and I will never forget it.

These days I have a solar system with a 100 volt battery (thirty lithium cells) and regularly come into full contact with that, and never feel even a slight tingle.
I guess us old farts tend to have have very dry skin.

So laugh at me if you like, call me a wimp, a coward, or totally crazy.
But I am a retired power electronics engineer, very used to working around dangerous high voltages as part of my job.
That is not a problem, because I know where the dangerous voltages are. Electrocutions always come completely unexpected.


The idea of working and maintaining a system with 350 volts of dc in a salt water boat just scares the shit out of me.
I have no problems working with 350 volts dc on an EV or solar system in a dry environment.
Salt and damp changes everything.

Nobody wants to tell you crazy. But in your story, it was your mistake and the person who left the exposed terminals. It is the same if I put my fingers into the 120V socket, get an electrocution, and tell everyone how dangerous it is. I respect your experience and would really appreciate it if you would share your insides on how to make things even safer but for now, it all sounds like an off-topic. Everyone knows that electricity is dangerous.

P.S. I think I have to update my first post because for some reason everyone still thinking about 350V DC…

 

[HOTOREL]

Consider two 48V battery banks wired in series. Place a bypass diode across each (reverse polarity diode, sized and heatsinked to carry 100% of current.) That should protect their BMS from over-voltage if they disconnect.
That gives you 96VDC.

Alternatively, parallel multiple 48V batteries. Connect three European 230V inverters as 3-phase. Feed output to VFD to power motor.

3x Sunny Island would be 18kW.
I think SolArk (check out Deye for 230V model) being 120/240V split-phase and supporting 120/208Y as well, could probably be wired for 240V to neutral.

Other inverters should work - to feed a VFD.
If you had 360V or so battery, that could feed VFD directly. I don't think you can get away with stacking 48V batteries that high, due to voltage rating of EMI components.

Can you tell me more about using the diode to protect the BMS? I do not really get an idea of how it is possible. And yeah the trick with three inverters is pretty smart. I will think about it if I will go 230V or more but for now, I’m going to stay at 100.8V)

 

[Warpspeed]

Nobody wants to tell you crazy. But in your story, it was your mistake and the person who left the exposed terminals. It is the same if I put my fingers into the 120V socket, get an electrocution, and tell everyone how dangerous it is. I respect your experience and would really appreciate it if you would share your insides on how to make things even safer but for now, it all sounds like an off-topic. Everyone knows that electricity is dangerous.

P.S. I think I have to update my first post because for some reason everyone still thinking about 350V DC…

What really surprised me was that 12 volts could even produce an electric shock at all.
The severity of it has remained vividly in my memory for over sixty years.
As I work with electricity, I have had numerous bites and tingles over the years, but that particular one I will never forget.

 

[yabert]

You should check their website https://www.qsmotor.com/

I know QS motor and their 12kW car hub motor is attractive. But spec and reality can be different. A sprint of few minutes in the rear of a motorcycle at 12kW is different of powering a boat at 12kW for hours.
Still, this 12 kW motor is probably a 4-6 kW motor at 48V.

The motor I have should provide more than 200Nm

Yes, but how long. A 1 kW bike hub motor can provide 1000Nm... for 2 sec before melting

If you have more then 2 cells connecter in parallel in your battery pack it is already not good.

Ha! really. Ok, I have to tell all the engineers from Tesla, GM, Ford, VW, LG chem, BYD, CATL and other they are idiot because they connect cells in parallel.

 

[HOTOREL]

I know QS motor and their 12kW car hub motor is attractive. But spec and reality can be different. A sprint of few minutes in the rear of a motorcycle at 12kW is different of powering a boat at 12kW for hours.
Still, this 12 kW motor is probably a 4-6 kW motor at 48V.

This is exactly why I want to test it out. There is no data on who would ever try to do it.

Ha! really. Ok, I have to tell all the engineers from Tesla, GM, Ford, VW, LG chem, BYD, CATL and other they are idiot because they connect cells in parallel.

I don't know about GM, Ford, and others but I studied how Tesla builds their batteries. I've had an internship there and they use the same ideology. They have groups of cells connected in parallel after those parallel groups connected in series in modules and after big modules connected in series into the whole battery pack. At the low level yes, they had to connect 30-70 cells to one balance wire but it was a physical limitation because they had to connect thousands of cells. They are going away from this with each new iteration but the main idea is the same they don't create two high-voltage batteries and just connect them together.

 

[Warpspeed]

How are these super powerful EV motors cooled ?
I have absolutely no idea, they do seem to be rather small for the power ratings.

 

[Hedges]

Can you tell me more about using the diode to protect the BMS? I do not really get an idea of how it is possible. And yeah the trick with three inverters is pretty smart. I will think about it if I will go 230V or more but for now, I’m going to stay at 100.8V)

Bypass diodes in a PV panel prevent current from being pushed through, which would cause a large reverse polarity and blow them out.

BMS in series are fine until they try to disconnect. Typically, someone might have 4x 12V batteries in series for 48V. If one disconnects, the load pulls battery+ down to battery-. A BMS could have 36V from other batteries connected to its (12V) battery negative terminal. Its last cell would be at +48V. Other side of BMS FET would be at 0V, so FET sees -48V and will fail if not spec'd for that voltage.

My theory is that a reverse-biased diode across each battery & BMS assembly would prevent application of that volage. But it needs to be able to carry the current, if remaining 36V is applied to load. In your case, 2x 48V packs, so current if 48V feeds motor when one BMS disconnects.

Just an in-my-head design, but I think it is valid.

 

[HOTOREL]

Bypass diodes in a PV panel prevent current from being pushed through, which would cause a large reverse polarity and blow them out.

BMS in series are fine until they try to disconnect. Typically, someone might have 4x 12V batteries in series for 48V. If one disconnects, the load pulls battery+ down to battery-. A BMS could have 36V from other batteries connected to its (12V) battery negative terminal. Its last cell would be at +48V. Other side of BMS FET would be at 0V, so FET sees -48V and will fail if not spec'd for that voltage.

My theory is that a reverse-biased diode across each battery & BMS assembly would prevent application of that volage. But it needs to be able to carry the current, if remaining 36V is applied to load. In your case, 2x 48V packs, so current if 48V feeds motor when one BMS disconnects.

Just an in-my-head design, but I think it is valid.

I was thinking of disconnecting the load at all as soon as one of the batteries goes Into over-discharge protection. Because if there is one of the batteries triggers this protection it means all others will trigger it soon. It means that the battery is drained and I had to turn on the generator way before it happened. And in this case, I don’t need to deal with increased current for the rest of the battery because it will be already disconnected from the load

For now, I just think that I will charge my battery to 100% before heading somewhere, and as soon it reaches 50% I will run the generator to move it back to 80% and so on.

 

[yabert]

How are these super powerful EV motors cooled ?
I have absolutely no idea, they do seem to be rather small for the power ratings.

QS motor? Air cooled. Yes, very small and compact.
Still there are not magical and they will overheat fast in any application who don't imply to move a tiny/lightweight motorcycle/scooter who continuously receive important air flow.

 

[yabert]

This is exactly why I want to test it out. There is no data on who would ever try to do it.

Probably near you, Justin from Grin did some test with their hub motor.

 

[HOTOREL]

Probably near you, Justin from Grin did some test with their hub motor.

Sorry that I disappeared again for quite a while. Yep I spoke to them. The problem is that they use 48V or 72V motors. This voltage is too low to build a power-efficient system. This is why Tesla now moved to 800V DC. Plus they didn't release this product to the public yet. And they don't really know when or if they will do it.

 

[HOTOREL]

So yeah here is the update! It is running! So the trials are going to start pretty soon. I need a couple of weeks more to finish the battery bank. For tests, I'm assembling a 24S18P 21700 Li-ion bank.

Check out the video at 10% of the power
P.S. Does anybody know how to remove the 25% power output limit on the fardriver controller in reverse?

And also I started to prepare the flybridge for the installation of more panels. Because I want to have there 8 550W panels in total. So the radar arch was banned from the top of my yacht. I also have a video about the process if you are interested.

 

[HOTOREL]

QS motor? Air cooled. Yes, very small and compact.
Still there are not magical and they will overheat fast in any application who don't imply to move a tiny/lightweight motorcycle/scooter who continuously receive important air flow.

Yep, you're right but when you are going higher in voltage you have less heat. Again I still have an idea just to put there two Tesla drive units XD
I will do the trials on the 2.5kW electric motor that is already installed on the drive shaft and will decide what way I should go. Tesla or QS motor

 

[yabert]

Thanks to share vidéo. Nice to see this going foward.

The problem is that they use 48V or 72V motors. This voltage is too low to build a power-efficient system. This is why Tesla now moved to 800V DC.

No.
A 48V motor can be 96% efficient and a 800V motor can be 96% efficient.
The difference is the first one will give few kW and the second one will give around hundred kW.

If you plan to play with Tesla motor, the permanent magnet one on the rear of model 3 and Y is quite popular, efficient and powerful.
Ingenext sell all the modules to hack Tesla motors or batteries.

Still, if you plan to go relatively low voltage at 90V (what I consider a good idea), there is many other efficient motors working at that voltage.
But they will require a gear ratio as most run at 4000-7000 rpm.
I have an eye on the Montenergy ME1507 motor for a futur sailboat build. It's efficient, compact, powerful and come in air cooled or water cooled version.
You can also look at crash Zero motorcycles on auction to reused motor/controller from them as they work at ''low voltage'' of 102V.

 

[HOTOREL]

I'm here to drop a quick update on the project:
https://www.youtube.com/live/THa0V-V7_vc
Here I did answer most of the questions and told pretty much everything about the current setup. We also not planning to use Tesla Drive units anymore because I found way cheaper and more interesting alternative.

 

[yabert]

Man! please less bla-bla and more images from: motors, battery, shafts, propellers

 

[wpns]

Man! please less bla-bla and more images from: motors, battery, shafts, propellers

C’mon, it’s only an hour and 20 minutes.