Air Cooled vs Watercooled BLDC Motor

[Karottop]

Hi There,

I'm new to the forum. I've been working on overhauling an old Ray Electric Outboard lower unit with an air-cooled BLDC motor. The controller came from the factory with a battery current draw limit of 85 amps for some reason. I only know that because I finally got the cable and was able to read the parameters off the controller.

Under those conditions, I ran the motor at 85 amps without any issues for about 30-45 minutes on the lake. I've installed two 150 CFM fans on the outboard cover to help cool the equipment.

Now that I have the cable, I've set the limit to 185 amps. I expect I'll be able to scoot along much faster and maybe even get on plane at that new current level which has been my goal all long. My question is cooling. I expect I won't need to run the outboard at that amp draw for more than about 30ish minutes at any given time. With the cooling fans on, do you expect I'll need to stop to let the motor/controller cool off within that 30-minute period? The rep at Golden Motor said I could get away with the air-cooled version, but I'm curious to hear your perspective

[Karottop]

I tested it out today for anyone interested. The short answer is, if you intend to run the motor at more than 100 amps (I have the 48v) then you should opt for the liquid cooled version. Even with fans, it doesn't cool down fast enough. I could run about 200 amps through it for about 10 minutes because the controller started dialing back the throttle gradually.

[Bikemad]

Hi andto the forum.

I was hoping that someone with first hand experience of GM's water cooled motors would have replied to your initial question, but as they haven't, I'll give my opinion instead:
I don't think that the water cooled motors will be able to self prime, as I'm pretty sure that they don't have any form of integrated coolant pump. I think it's simply an extension piece with integrated coolant channels that bolts on the end of the motor, similar to the one shown below:



The coolant has to be externally pumped through the cooling plate using an electrical pump, or possibly an open inlet that effectively forces the water through the motor cooling pipes using pressure generated by the propeller.

I tested it out today for anyone interested. The short answer is, if you intend to run the motor at more than 100 amps (I have the 48v) then you should opt for the liquid cooled version. Even with fans, it doesn't cool down fast enough. I could run about 200 amps through it for about 10 minutes because the controller started dialing back the throttle gradually.

It might be worth trying to check the temperature of the controller's cooling plate to confirm that the controller itself is not getting too hot.
I'm not sure whether the temperature of the controller itself can automatically reduce the power going to the motor, or whether it would simply cut the power completely if the controller becomes too hot.

Alan
 

[Karottop]

Very helpful, thank you Alan!

Let’s say the controller was getting too hot, how would I cool it down? I have the VEC500

[Karottop]

Also, for what it’s worth, there seems to be a safety mechanism in the software that remembers the lowest amp draw you pulled while overheating. Next time I took the boat out, I couldn’t pull more than 119 amps which is where it was when I overheated it last. It gradually stepped down to that level over a ~30 minute period. The next time I took it out when the motor was cold, the amp draw slowly increased the more I ran it. By the time I was done running it at max throttle for about 5 or so minutes, I was pulling 123 amps. This tells me it’s stepping the amp draw back up for as long as it’s not overheating.

I bought the liquid cooled motor so I’ll test that theory next time I take it out to see if I can get back up to 200 amps

[Bikemad]

Let’s say the controller was getting too hot, how would I cool it down? I have the VEC500

Check out this post for more information on cooling the controller.

Also, for what it’s worth, there seems to be a safety mechanism in the software that remembers the lowest amp draw you pulled while overheating. Next time I took the boat out, I couldn’t pull more than 119 amps which is where it was when I overheated it last. It gradually stepped down to that level over a ~30 minute period.

According to the programming software, the motor temperature will cut the current back to "Level 1" when it reaches 120°C  and "Level 2" when it reaches 130°C.
If the motor temperature exceeds 150°C, it should stop the motor completely.
However, the value that really puzzles me is the "Motor temperature protection exit value" which seems to be very low (20°C).
Does this really mean that full current (or any motor use, if it had cut out completely) would not be available until the motor temperature had dropped below 20°C? 

The next time I took it out when the motor was cold, the amp draw slowly increased the more I ran it. By the time I was done running it at max throttle for about 5 or so minutes, I was pulling 123 amps. This tells me it’s stepping the amp draw back up for as long as it’s not overheating.

Something else to consider might be the battery itself, as its power output can also be affected by temperature.
If it is too cold at the beginning of the trip, you may find that it cannot deliver the expected current until the cells have warmed up sufficiently.

The battery's state of charge will also affect the amount of voltage sag under load, which could cause a dramatic drop in power if the voltage at the controller falls low enough to trigger the controller's low voltage protection, which I think is set to 44V by default.
If you want to monitor the voltage drop under load, you should attach your voltmeter leads to the B+ and B- terminals on the controller.

Let's hope that you are able to get the battery current back up to 200 amps again.



Alan
 

[Karottop]

Very interesting. Golden Motor says the VEC500 is tuned for the 10 KW BLDC motor however it appears to be a weaker and less sophisticated controller when compared to their line of universal EZ-kontrol controllers. Specifically, the EZ-B481000 appears to be designed for a 10 KW motor but it also comes with liquid cooling ports and Bluetooth built in. Neither of which is available on the VEC500.

Does anyone have experience using the EZ-controller series with the BLDC motor? I may just go that route

[Karottop]

Update:

I sent a message to Golden Motor Support about the EZKontroller's support for the 10KW BLDC motor. The thread is below. I'm not sure why I'd need anything close to 800 amps of phase current since the 48v motor only appears to support 400 amps max.

Message to Support:

Hi there,

I have a 48v 10KW BLDC motor. I have two questions:

1. If I wanted to use the 48v EZkontrol, would the EZkontrol B481000 model be the correct choice?
2. Is there any disadvantage to using this controller over the VEC500?

Response:
Thanks for reaching out. Here are the answers to your two questions:

1) Yes, the EZkontrol B481000 is rated for 10kw motors. It has a max phase current of 1000 Amps.

If you don't need that much power, you could move down one level to the EZ-B48800 which has a max phase current of 800 Amps.

2) One feature of the EZkontrol controller that could be counted as a disadvantage depending on your setup is that it is programmed using a mobile app instead of with a USB cable.

This wouldn't be a disadvantage, but programming is only supported on the android mobile app at the moment, and not the iOS mobile app.

In the description of this product page there is a lot of additional information about the controller. We also made the purchase options simpler.

https://goldenmotor.bike/product/ezkontrol-48-volt-universal-bldc-controller/

Follow up response:
I just wanted to send an update on this ticket.

Programming the EZKontrol is possible with iOS, we are planning to make a video for it soon to show how to program the controller. So, Android and iOS programming is supported via Bluetooth, but it is not possible to program with a computer.

----------------------------------------------------------------------------------------------

I took Bikemad's advice and bought a water-cooled heat sink for the VEC500 controller because it was cheaper than buying the EZKontroller. My theory was that the firmware would step up the amperage to the motor incrementally so long as it was operating below it's temperature threshold since this is how it worked when it overheated. Unfortunately, after running it for 20 minutes that's not what happened.

When I reached 200 amps previously, I had the stock prop on the Ray Electric Outboard lower unit. On this test run and some others before it, I was using a much larger and higher pitch 14x18 three blade prop. It has much more bite and I was hoping it would propel the boat at the same speed at a lower motor RPM in an effort to pick up some efficiency since the motor has so much torque. Since it hasn't worked, I'm going to try putting the old prop back on to see if it makes any difference. I can't imaging why a larger prop would prevent the max amp draw by the controller/motor, but we'll see. If that doesn't work, I'm out of ideas as to what's limiting the amp draw. I highly doubt it's the batteries because I'm running three 48v LiFePO4 120Ah batteries in parallel each capable of putting out 120 amps of continuous current meaning the bank can put out 360 amps of continuous current. Even if they were cold I would think they'd be able to at least put out 200 amps especially since I was able to pull 200 amps earlier this year when it was the same temperature or cooler. Nevertheless, I'll report back in the summer if I don't learn anything before then.

[Pontus]

Hi there,

First of all : Unless the motor rpm somewhat matches the rpm of the prop, you need some kind of gear box.

The peak power of the GM 10 Kw BLDC is at around 3700 rpm, which is way to high for a 14x18, so unless there's gearbox inside the leg, one would bee needed.

I've gone through the same thing although with the motor mounted as an inboard, thinking that the great torque of an electric motor would solve that. Even though I had water cooling blocks mounted on the VEC-500 if sometimes got above 75 °C.

During my build of a reduction gear I swapped the VEC-500 for the EZ-kontrol B48-1000. Now the controller barely gets over 40 °C after several hours of use and the motor tops at 65 °C.

All reasoning and calculations about the reduction gear is documented in this blog post. Google translate available.