Water Cooling Mass Flow Rate?

[GrandeDan]

Hi All,

I am working on using the liquid cooled 5kW BLDC motor to run my boat. I am having trouble with cooling though. I have a 5kWh battery and am trying to run wide open for that hour. There doesn't seem to be enough cooling and the motor overheats. Does anybody know the mass flow rate of water that needs to be running through the cooling passage to cool the motor?

Side note: I am using sea water and not a heat exchanger.

[GrandeDan]

I should add that the controller model is EZ-A48500

[Ziper1221]

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.

[GrandeDan]

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.

[Bikemad]

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?

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

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.

Alan