GoldenMotor.com Forum
General Category => Electric Boat Conversions => Topic started by: Lollandster on July 21, 2015, 10:16:22 AM
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hi, I'm planning on doing a conversion of a double-ender boat. This is a boat that is designed to plow through the water and not over it (displacement rather than planing boat) and has a 1 cylinder 8hp diesel engine mounted in the center of the boat. The boat is 21 feet. The boat design is very energy efficient and should be optimal for converting to electric propulsion. This is not a fast boat and is not designed to go faster than about 6 knots.
My plan is to install a 10kw motor and about 10kwh of batteries to start with. I would like to use lithium, but for this project to be possible on my budget I'll have to start out with AGM batteries. The boat shall be used on saltwater so I need a closed fresh-water cooling solution, probably with a copper pipe running underneath the boat to cool the water, I rather not use a two pump system, but I don't know how much cooling the motor will need.
The axle from the propeller to the engine is fairly long to allow a shallow angle from the propeller to to engine. The electric motor is smaller than the diesel engine and will fit lower in the keel so the axle may be shortened and the motor placed closer to the stern. The propeller has adjustable pitch and may need to be swapped for one that is fixed pitch. I haven't worked out all the details yet. I may need some custom parts to fit everything together.
While an electric motor is suppose to be very quiet I still expect there to be some noise from the whole assembly of cooling pump, controller, motor and axle. I'm therefore planning to insulate it very well.
I will blog everything I do when I get started.
Any comments on this project would be very appreciated. I know this forum has a lot of knowledge about electric propulsion.
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Hi Will you choose a low angle fixed prop du to higher rotational speeds? Any problem with cavitational corrosion? In that case you might consider to keep the variable pitch
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Hi Will you choose a low angle fixed prop du to higher rotational speeds? Any problem with cavitational corrosion? In that case you might consider to keep the variable pitch
The variable pitch propeller use a special gearbox that allows the axle to be moved back and forth to change the attack angle. With an electric motor I'm hoping to eliminate the gearbox and that will make it difficult to use the variable pitch. I'm also thinking that the propeller probably doesn't have the most efficient design. I'm not sure yet if I can get away without a reduction gear, but if I can I certainly need a smaller propeller.
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A smaller propeller is likely to be a lot less efficient than a larger diameter one, and the higher rpm of the propshaft may also cause more frictional losses and result in increased vibrational noise, which will probably require far more accurate balancing of the whole propshaft assembly in order to reduce it.
A toothed belt and pulley reduction system might be the best solution, but you will need to do some research to find the optimum rpm to suit both the propeller and the motor.
(http://cleanemarine.yolasite.com/resources/Thoosagearing.jpg)
Why is there reduction gearing on an electric boat motor?
There are 3 great reasons for using gear reduction.
- It’s easier on the motor to spin the prop which means there is less current draw from your batteries.
- If by unfortunate chance you hit your prop, the pulley and belt will absorb the impact vibration from the propshaft. If the propshaft is directly linked to your electric motor the chance of damage is significantly more should an impact occur.
- Gear reduction produces Torque. The torque produced by the output is inversely proportional to the amount of gear reduction. Say what? In short, if you have a 2:1 gear ratio then the prop speed turns 1/2 as fast but has twice the torque! It’s physics.
Alan
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Thanks for the info Alan. I was afraid that a reduction gear was necessary when I saw the torque curve for the motors. But it would be easier without one. Noise and wear from the prop shaft is a concern and a belt solution would be less noisy than a gearbox.
I have to check out the thoosa system, it looks like a good solution. If they ship to Norway and aren't too expensive (like some of the other solutions I've seen) it might be a buy.
Edit: You wouldn't know who makes the thoosa system? It says it is danish manufactured, and Danmark is only 3 hours away with boat.
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After reading about the Thoosa system it seams to be using brushed air cooled motors, and the price was rather high. But I like the gearing system and I think I can easily design something similar for the GM motor with some off the shelf belt drives and some custom parts from the local water-cutting center.
Thinking about it I think I can use the existing propeller and shaft by making a motor mount that allows the motor to be moved (Now that I have abandoned the idea of direct drive). That way I can adjust the propeller attack angle until I find the sweet spot between speed, torque and efficiency. It may yield a better result that a fix propeller because it can be very difficult to calculate the correct propeller size and very expensive to do the trail and error approach.
I need to find out what the rpm of the shaft is with the current engine so I know the ballpark gear ratio to aim for. I guess this is a good reason to buy an optical RPM counter ;D.
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If the motor controller is air cooled you might also want to consider using a liquid cooled heat sink plate to ensure it stays nice and cool inside the hull.
(https://i.imgur.com/vcIFEAu.png)
Perhaps the controller heatsink and the salt water/coolant liquid heat exchanger could be combined into a single unit by sandwiching two of these units together with the controller bolted on top of the cold salt water one?
You might also want to take a look at this YouTube video showing what's inside the GM 48V5kW water cooled motor (https://www.youtube.com/watch?v=ylgf6YwN8Fc).
Alan
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Having done more research I find that I need to do even more research.
For now I'm going to make a CAD model using the 5kw motor as that seams to be a better motor than the 10kw (and cheaper too). I know a similar boat to mine (Polar 20 electric) uses a 2,2kw motor with success.
As I've done with the hub motors from Golden Motor, I will try to install a temperature sensor on the windings. It seams to be fairly straight forward to do that based on the youtube video showing the internals.
The propeller I have on my boat seams to be designed to work at 500-1000 rpm. Since the propeller is variable pitch it probably is very forgiving. I'll try to go as slow as possible to reduce wear and noise, but I have limited space around the propeller shaft so that is going to dictate the maximum size of the secondary pulley. Using more than one belt is not acceptable to me at this point.
For cooling the controller I have already thought about using a cooling plate. If I can't find one 'of the shelf' somewhere, it should be fairly easy to mill a cooling path in a aluminium plate and glue a second plate on top with threaded holes for the inlet and outlet. I have access to a mechanical shop where I work.
If anyone has a good tip for the throttle I'm all ears.
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I found that the biggest ratio I can fit is 4:15. I think I can work with that. Now I just need to design the mounting hardware (the crib).
3DPDF (https://www.dropbox.com/s/5he205syeeevyxl/5kw_motor_general_placement.PDF?dl=0)
(http://s25.postimg.org/gmyax09in/5kw_motor_general_placement.png)
Figure showing a model of the space available in the boat and how I might place the motor.
(http://s25.postimg.org/5m35rzh9r/belt_length_calculator.gif)
Screenshot from http://www.bbman.com/catalog/belt-length-calculator.html showing the belt I used in the model.
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It's looking good so far, but I have just though of something else regarding your variable pitch prop.
I presume the existing diesel engine uses a gearbox to change the direction of the propshaft for reverse, otherwise the thrust in reverse would be very inefficient if it was achieved by simply reversing the pitch of the prop blades.
If it doesn't reverse the direction of the propshaft, and has a thread on propeller boss instead of a spline or key-way, it could unscrew the propeller if you ran the electric motor in reverse instead of reversing the pitch.
I realise that it's very unlikely to be a screw on prop assembly, but I thought I would mention it just in case.
Alan
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It's looking good so far, but I have just though of something else regarding your variable pitch prop.
I presume the existing diesel engine uses a gearbox to change the direction of the propshaft for reverse, otherwise the thrust in reverse would be very inefficient if it was achieved by simply reversing the pitch of the prop blades.
If it doesn't reverse the direction of the propshaft, and has a thread on propeller boss instead of a spline or key-way, it could unscrew the propeller if you ran the electric motor in reverse instead of reversing the pitch.
I realise that it's very unlikely to be a screw on prop assembly, but I thought I would mention it just in case.
Alan
Good thinking. You are of course correct, the propeller is screwed on. Loctite 307 is used on the threads according to the manual. I can't find much info on Loctite 307, but I guess reversing should be done with caution.
Reversing the pitch with the electric motor mounted is not something I'd like to tackle. The engineering needed to make that work is too much for this project.
If I need to change the propeller for a fixed one I also need a new shaft. I have never changed the propeller shaft on a boat before so I don't know how hard that is going to be. The mounting solution I'm working on for the motor should allow some alterations to the shaft angle if that becomes necessary.
For now I'll just work under the assumption that I can use the current propeller. I'll tackle the problem with a new propeller and shaft later if it necessary.
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Quick update:
I have found that I need to up the belt width to 1in and increase the tooth count on my primary to 18 teeth. The increase in belt width is because I'm close to the limits of what a type L belt can do when it comes to power and I can't easily go to type H with the rotation speed of the motor (or so I understand from what I've read today). The increase from 16 to 18 teeth is because I want to use a taper bush and 18 teeth is the smallest pulley with a taper bush hub.
The picture below is a render of what I've drawn so far of the mounting system. It is still far from complete, but it should show the direction I'm heading. Between the two views I've put the shaft bearing, it is included in the model but is impossible to see from the views. I intend to weld that to the mounting plate as I'm not competent enough with the milling machine to machine it into the plate. Everything needs to be possible to make with only a router (water cutting), a lathe and hand tools. If I can avoid milling I will, although I have access to one.
(http://s25.postimg.org/uh5150vn3/render2.png)
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Using a simple idler pulley as a belt tensioner would eliminate the need for all those slotted holes and would make it a lot easier to change and tension the toothed belt, as it's much easier to slacken two bolts and rotate a tensioner than slacken all four motor bolts and lift a heavy motor with wires and water pipes attached to it with one hand while you struggle to tighten the bolts up again with the other.
It could also be used in conjunction with a slightly longer belt to allow more wrap around on the smaller pulley which would also spread the load over more teeth:
(http://www.nzdl.org/gsdl/collect/hdl/index/assoc/HASH011f.dir/p041b.png)
Alan
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I did consider a tensioner and I decided not to bother. But I was only thinking about the wraparound benefit, I didn't consider how heavy the motor is. I shall think more about it an maybe implement one.
I may have to dig out one of my old text book from school and re-read the belt and pulley chapter, I think I still have the book somewhere.
EDIT:
Another way of doing the tensioning is to to have one screw as a pivot point and the rest in slotted holes. I try to demonstrate with the figure below
(http://s25.postimg.org/5f2hs6p7z/slotet_screws.jpg)
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I haven't been working much with the design lately because of some problems with my computer. The water cooling pump stopped working and overcooked my CPU. Now my computer is unstable. On the bright side I now have a descent water cooling block to cool the controller.
I ordered the motor (http://www.goldenmotor.ca/products/48-Volt-5KW-BLDC-Motor-Liquid-Cooled.html) last night from Gray Salo.
I think I'll order a controller from Kellycontroller. The KLS7250D (http://Kellycontroller.com/kls7250d24v-72v420asinusoidal-brushless-motor-controller-p-1337.html) seems like a good match. Please correct me if I'm wrong.
John
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Quick update:
I have mostly played with the controller lately and since it isn't a GM controller I won't post about it too much here.
The motor came from GM Canada in one piece, no problems (except for the Norwegian customs being very slow).
The motor came with two hoses for the cooling at about 1 meter each. The hoses and their connectors look like standard pneumatic 8mm hoses, so that is going to be easy to find.
The hall effect sensor cable happen to have the exact same connector as the one on the Kelly controller. It was simple Plug and Play. And with the automatic hall identification feature of the controller I could connect the phase wires as I pleased with no worries.
The motor did not make as much noise as I feared (It probably helps that the controller is sinusoidal while the controllers used in all the youtube videos probably aren't). I haven't tried it under load yet.
I expect to have the boat on dry land by the end of the month. I'll find out if I can keep the propeller then and also find out how exactly to do the cooling.
(http://s25.postimg.org/rztts7hnv/IMG_0223.jpg) (http://postimg.org/image/rztts7hnv/)
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I didn't work on this project last year, but now I'm back on it.
I made a small dummy shaft to simulate the propeller shaft and used the laser cutter at work to cut ot a wooden prototype of the future motor fixture.
Attached is a photograph of my proof of concept.
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Hello everyone,
I would like to know 2 or 3 more things about my GM 10 kW.
1) there are two identical sockets multi-contactors (black cable) that come out of the motor, why?
2) there is a "cruise" connector coming out of the controller, what is it for? And how to use it?
Thank you for your kind response.
Nautical regards.
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1) The 10, 15 and 20kW motors have twin stator assemblies, which means there are two separate sets of phase windings and wires and two sets of Hall sensors and wires.
Both sets of phase wires must be connected to the controller, but only one Hall sensor connector needs to be used.
The other unused connector is basically a spare, which can quickly be utilised in the event of a hall sensor failure by simply unplugging the failed sensor's connector and plugging in the unused connector instead.
2) The Cruise connector is a very basic cruise control function (throttle hold) which comes in handy on car and motorcycle conversions, but I don't suppose it will be of much use in a boat conversion as you probably have a friction type throttle that stays where you set it anyway.
On a car or bike the cruise wire would connect to ground (B-) via a momentary push switch that you simply press (and release) while the throttle is in the required position, and the motor will then continue to run at the set throttle position even though the throttle is released.
The cruise function is cancelled by either pressing the cruise button again, or applying the brakes.
Alan
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Thank you Alan, for your explanations clear and precise.
Another question to which, you could perhaps answer:
I have equipped the internal trottle cockpit proposed by GM (ref TRC-010).
It is normally provided to measure the acceleration with a "stop" midpoint separating the "forward" and "reverse" steps.
Currently it only serves as an accelerator and I reverse the direction of rotation with a switch.
Is there a better way to do this, by setting the VEC 500 for example?
Thanks again,
Nautical regards.
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With the VEC controllers, I think you need to change the "Speed throttle type" parameter to enable Forward and Reverse with a Stop position in the centre of the throttle movement.
Check out this post (https://goldenmotor.com/SMF/index.php?topic=6162.msg34398#msg34398) for more details.
If "Potentiometric" is not an available option from the drop down menu, I suggest you try "Potentiometer" instead. ;)
Alan
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Thank you Alan,
As soon as I go back to the boat, I try that.
Have a good day.
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Hello Alan,
Back on the boat, I connected my controller heat sink to the "keel-cooling" used to cool the old thermal engine. I managed to maintain the temperature of the VEC500 at about 80 ° C and I can turn for several hours without making it safe.
I also installed 20 kW of Lithium batteries and there it is full satisfaction, as they recharge in a couple of hours only with my photovoltaic cover.
On the other hand I can not exceed a speed of 5 km / h: when I push the potentiometer more, it is safe.
How do you explain this and how do you remedy it?
As shown on another subject, the motor is in alignment with the shaft and I use the "reverse" switch to go forward. Is there a report?
Thank you for your advice.
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I am pleased to hear that the heatsink has cured the cutting out problem that you had before, but did you manage to get the throttle working correctly by changing the controller settings?
You can swap the following wires so that the motor runs in the correct direction without relying on the reverse switch:
The Blue and Yellow thick Phase wires need to be transposed and the Green and Yellow thin Hall sensor wires must be transposed at the same time.
Do not try running the motor with just the phase wires swapped (or just the Hall sensor wires swapped) as both must be swapped for the motor to run correctly. ;)
I'm not sure if the speed limitation is due to settings for the switched reverse mode, or whether it is limited by the motor rpm/battery voltage (or insufficient load on the motor).
When you push the throttle further, does the motor draw more current, increase in rpm, or sound any different?
Does the motor draw more current or run faster when the reverse switch is turned off (with the boat going backwards in your case)?
According to the dynamometer test data (https://www.goldenmotor.com/eCar/HPM48-10000.pdf) the 10kW motor produces maximum power and torque below 3500 rpm. How does this compare to the original diesel engine's maximum rpm?
If your motor is turning much faster than 3500 rpm, then it will be unable to produce as much power:
10,070.23W @ 3507 rpm
7,385.05W @ 3855 rpm
5,067.70W @ 4091 rpm
1,397.57W @ 4563 rpm ???
Check out this post (https://goldenmotor.com/SMF/index.php?topic=6127.msg34262#msg34262) for a solution for a jetski conversion with an unexpectedly low power output.
Alan
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Hello Alan,
Thank you for your quick reply.
I recalibrated the engine speed to 3500 rpm.
But that does not change anything.
The engine is still not running.
I will try to rewire it in forward direction by modifying the cables as you indicate and I keep you informed.
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J'ai l'impression au bruit que lorsque je suis en marche arrière (la marche avant conventionnelle), le moteur tourne plus vite.
Je vais donc modifier l'ordre des cables.
Peux-tu me confirmer la configuration des nouveaux branchement car ceux du connecteur "Hall" ne sont PAS changés de la même façon que pour le moteur ?
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I get the impression that when I am in reverse (conventional forward running), the engine runs faster.
So I will change the order of the cables.
Can you confirm the configuration of the new connections because those of the "Hall" connector are not changed in the same way as for the engine?
The two pairs of Blue and Yellow Phase wires must be swapped over on the controller terminals, and the Green and Yellow Hall sensor wires must be swapped on the Hall sensor connector.
It is better to swap the the Green and Yellow Hall sensor wires on the controller side of the Hall sensor connector if possible.
But if you are only able to swap the the Green and Yellow Hall sensor wires on the motor side of the Hall sensor connector (and it correctly reverses the motor's direction of rotation as expected) then I suggest that you also swap the Green and Yellow wires on the unused Hall sensor's connector to avoid problems in the future if the unused set of Hall sensors are plugged in. ;)
Alan
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OK, it's much better at the torque!
Thank you.
This means that the operation is not symmetrical between forward and reverse.
I will resume my new tests and I will report to you.
Good night.
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Hi Alan,
As expected, I'll give you my test report.
It is better in speed with the reversal of the direction of rotation, but after about ten minutes, without any variation of the potentiometer, the engine slows down in revolutions and if the gas is increased, nothing Does not change. If the system is still pushed, the system becomes safe.
Would you have explanations and remedies?
Nautical regards and thanks.
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Without a lot more information (controller settings, battery voltage under load, current draw and temperatures of the motor and controller etc.) it is difficult to know what is causing the problem, but if the motor is slowing down, it may be due to one of the following:
- The motor is getting too hot (or the "Motor temperature limited(°C)" is set too low)
- The controller is getting too hot
- The battery voltage is dropping too low under heavy load
- The 50% speed limit voltage (V) is set too high
The internal Sine Wave controllers used on the GM hub motors will automatically reduce the current if the battery voltage reaches the minimum voltage setting in order to prevent the battery voltage from going below the set limit, but I'm not sure if your controller does the same.
What does your battery voltage read under load, and how much current is being drawn (Ampères) when the motor starts to slow down?
I am also confused by one of your previous comments:
I also installed 20 kW of Lithium batteries and there it is full satisfaction, as they recharge in a couple of hours only with my photovoltaic cover.
Is this 20kW of maximum power output, or 20kWh of stored energy?
The maximum Power output that a battery can produce (measured in W or kW) and the total Energy stored in a battery (measured in Wh or kWh) are completely different.
A 48V 5Ah LiPo pack with a discharge rating of 90C can physically produce an output of 21.6kW at the maximum rated current (5 x 90 x 48) for a maximum duration of less than 40 seconds, but it can only hold a maximum of 240Wh (48 x 5 = 240Wh or 0.24kWh) of stored energy. ;)
What is the actual capacity (in Ah) and the maximum continuous discharge current ("C" rating) of the "20kW of Lithium batteries" that you have installed?
How much power is generated by your "photovoltaic cover"?
20kWh of Energy @ 48V would require a battery pack of around 417Ah, and the total area of your "photovoltaic cover" would have to be very large to generate a continuous 10kW of power to enable a charging current in excess of 200 Amps :o to fully recharge a battery of that capacity in just "a couple of hours". :-\
Alan
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Hi Alan,
I will try to respond to your requests of elements in the best way so that you can analyze things.
- About the engine: no heating (because it is cooled by the water circulation system + coolant).
- At the level of the VEC 500 controller: the same cooling system, recently fitted with a temperature probe installed on the aluminum rear block, keeps the temperature below 80 ° C.
- Voltmeters installed indicate a voltage that does not drop below 49.2 V.
- I do not know where the setting is "The 50% speed limit voltage (V) is set too high"
I enclose in PJ a record of the controller's current settings.
- For the amperage at the moment when the engine starts to slow down, I can not say it does not have a measuring device capable of doing it on DC current in 48V.
- As for the lithium batteries I enclose their documentation, knowing that it is a pack of 4 racks wired in parallel.
- With regard to the solar charging of these batteries, if the sun is correct, after a navigation of 3 hours, the next day they are full again (a system of LED indicates on each rack, the rate of charge).
- The 4 panels which feed them through a Victron Blue solar 150/35 regulator, are of last generation (335 W nominal - 22% efficiency).
Nautical Regards and thanks.
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- I do not know where the setting is "The 50% speed limit voltage (V) is set too high"
I have just double checked some screenshots and it appears this setting is only available on the HPC controllers (not the VEC). :-[
Unfortunately, when I load your settings into the PI-800 program I get "Err" on the Nominal battery voltage parameter and most of the other parameters are blank, so I am unable to see what any your temperature, voltage, or current settings are. :(
Your batteries are 50Ah each, so that's a total capacity of 200Ah or 10kWh of Energy. :)
Your four solar panels should produce ~1.34kW output in total, which would take at least 7 hours 40 minutes to fully charge your battery pack if it was completely discharged at the beginning of the charge.
I still feel that this problem is temperature related (possibly the motor) so it might be worth checking there is sufficient coolant circulating through the motor and that no air is trapped within the coolant pipes causing an air lock (https://en.wikipedia.org/wiki/Air_lock)?
Have you installed a separate electric pump to force the coolant around the cooling circuit?
I'm guessing that the original motor will have had an integral belt driven water pump with a reasonably high flow rate and much larger diameter coolant pipes.
Does the coolant for the motor and the controller heat sink circulate in series or are the coolant pipes connected in parallel?
I'm wondering whether more coolant is taking an easier route through the controller heatsink leaving the motor with a reduced coolant flow.
Does the motor feel noticeably warm to the touch when it starts to slow down?
Did you apply thermal paste between the base of the controller and the heatsink to help transfer the heat more efficiently?
I am running out of suggestions, so I have emailed GM China to see if they can help to locate the cause of your problem and I will let you know what they say.
Alan
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Hi Alan,
I checked that the document exporting data from the controller was empty.
I do not understand why...
In the meantime, I have attached 4 photos of the controller's current settings so that you have the information.
Nautical regards and thanks.
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Unfortunately, I have not yet had a response from GM China, but here are a few suggestions I have made based on your attached settings:
- Rated motor speed (rpm) = 4500 This may produce higher speed if the lower motor torque is still sufficient to spin the prop at higher speeds
- High voltage protection value (V) = 55 (Recommended battery operating range is 45~54V)
- High voltage protection exit value (V) = 54
- Low voltage protection value (V) = 44 (Recommended battery operating range is 45~54V)
- Low voltage protection exit value (V) = 45
- Low voltage triggering current reducing (V) = 47
- Maximum phase current (A) = 286 or 338? (1.3 x Battery drawn current or 1.3 x Boost current?)
- Rated phase current (A) = 286 (Should be about 1.3 x Battery drawn current (A))
- Forward Speed ratio (%) = 100 (This should allow the fastest available motor speed)
I have suggested the ideal high and low voltage settings to match you specific battery pack, but it's possible that some of these settings may not be accepted by the controller, so you'll just have to see if they can be entered and saved successfully. ;)
Alan