GoldenMotor.com Forum

Hi andto the forum.

Unfortunately, I have no experience with either the HTM07KW motor or the EZ-A72400 controller so I don't know what sort of regen current output you might expect to see, or whether continuous regen operation would cause any problems.

The EZ-A72400 has a rated motor power of 3-6kW, but the HTM07KW is rated at 7kW with a peak of 18kW therefore the EZ- A72500 rated for a 4-7kW motor (or even the EZ-A72800 rated for 7-12kw motor) might be a better choice of controller if more power is likely to be required occasionally.

As the HTM07KW motor is rated for 92A @ 72V (6.624kW @ 1,950rpm) I'm guessing that it might produce a regen output of ~78A @ 84V maximum charging voltage (6.552kW @ 2,275rpm) if the regen efficiency is somewhere near the motor's power output efficiency.

I also noticed that the 7 and 11kW motors are both described as having "Natural cooling" yet they both appear to have liquid cooling pipe connections.

Alan
 

I am planning a conversion to electric of my 39ft Catana sailing catamaran with old, smelly 18hp diesels I am considering using two 7kw 72v axial flux  motors to  drive the existing sail drives directly, without gear reduction or the existing transmission  as the rated speed of 1950 rpm a good match for the prop speeds of 800-2000 rpm.  So two HTM07KW motors, one in each hull. Will these motors be okay operating for hours at a time? The motors will usually be operated at low power setting to extend the range, usually less than 2000 watts combined.  Usually the motors will only be used for a few minutes, to get the boat out of the marina unless there is no wind and we need to get somewhere..

So my main question is that I would like to know if using a third HTM07KW motor attached to a 12hp Kutoba diesel as a 72v generator with the same EZKontrol 800A controller as I am using for the drive motors. Can the controller handle regenerating  continuously? can the motor?  I hope for around 5-6kw from the 9KW (12hp) diesel at 1800- 2400 rpm.  The diesel is at it's tq peak from 2000-2600 rpm, so I would drive motor directly as it matches the rpm range  of the HTM07KW.  I already own the diesel engine.

I like that I would have three of the same motors and controllers as I'll be sailing long passages and could swap them if one failed. Keeping the generator light as possible is another reason I am considering this set up instead of a regular brushed alternator that would be much heavier. This generator would not be used too often, probably only a few times a year as the boat also has 1200 watts of solar, a hydrogenerator,  a wind generator and sails..  I am planning to use a 72v 300ah Lifepo4 battery for the motors.

I have no experience with the EZ Bluetooth App so I don't know what temperatures it actually monitors and displays. Are you sure that it's the motor that's overheating or could it be the controller?
 

I am positive it is the motor overheating. Through the GM monitoring app on WeChat, I can see them temp limit is 150degC for an alarm and 155degC for it to depower. 160 degC is Shutoff. I watch the live motor temp reading say 155degC. The controller also has temp limits to it, but I am reaching the motor temp limits before the controller.

Does your coolant flow in series through the motor first and then through the controller?

Coolant flows from controller to motor but with a small temperature differential between the inlet and outlet temp of the coolant, I don't believe switching the order of this will help very much. Especially because the motor temp is far hotter than the coolant. a 3 deg temp differential will not cause a huge difference in heat transfer between motor and coolant.

What rpm is the motor running at when it's drawing the 140 Amps?
If the motor speed is considerably lower than its rated 3,500 rpm it might be running too hot because the motor is being overloaded, in which case a smaller pitch/diameter prop (or possibly a gear reduction on the propshaft) may be required to reduce the load on the motor to allow it to operate at a more efficient rpm, which should then generate less heat in the stator windings.

Motor is running at roughly 3600 underload.

I would like to note that the cooling loop on top of the motor (where ALL the cooling is located) does stay cool. Cool enough I can touch it. But  moving down to the middle of the motor, it gets so hot on the outside casing that it could burn skin. I am wondering if GM just has an inadequate cooling system for their motor to run at full power for any extended period of time.

Check the outlet temperature of the water cooling. If the delta T is large, then you would benefit from moving more water. If the delta T is small, then you wouldn't, and the limitation is somewhere else.

The temperature difference between inlet and outlet is roughly 3 degrees F. It is not a large difference but with cooling, the more mass that flows through, the more heat will be exchanged. My issue though is that when I run the 5kW motor at 140 amps for an hour on a 52V setup, it still overheats. I would agree there is enough water cooling it but I should be able to run this hard for an hour. This is the only thing I can think of that would be fixable.

Hi Gilles,

Thanks for the update, it's good to know that you've managed to locate and rectify the problem.

I'm pleased for you that you now have it working correctly.

Alan