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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.
--- Quote from: Karottop on March 14, 2024, 02:14:20 AM ---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.
--- End quote ---
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
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