Burned 65161 Motor - Teardown

Hi Folks,
right at the beginning of the season, I managed to burn my trusty 65161 motor. I attempted to rewind it but no way.
I don’t understand how the motor was assembled in the factory.
The stator slots and ends are shut, and the winding in the slots is so tightly packed.
In the end, I ended up with a teardown for “education purposes”.
Here are some hi-res photos:

The weak point is the front and the back of the winding. The motor worked for 3. seasons in my iSUP with 20s battery configuration. The power never exceeds 6kW.

Link to hi-res photos: 65161 Motor – louiss13 – album na Rajčeti


Which kV and propeller did you use?

Reason why i’m asking is that 20s is a high voltage to run these motors (in the normal 100-120kV range)

The motor was 120 kv, I’m using 20s battery configuration because my Boston Swing 5300 batteries are so soft and they have a big voltage sag at 60A draw nearly to 65V.The prop is cut down Chinese alu provided by motor.


Thanks for posting this. I have a “new” version of this motor from Flipsky with the ceramic seal.

I’m new to all of this so would appreciate any extra education I can gain.

Did you do any maintenance or “extra” waterproofing to your motor over the 3yr period?

Can you estimate the number of hours on the motor from new to failure?

Do you have a positive or theoretical reason why the motor failed?

No extra waterproofing or additional oil filling, just as I bought.
I rode only in fresh water.
I looked at the Strava app, and every season I used around 45 hours of pure time in the water. I rode up to 210 km.
Total amount 135 hours and 630km to failure.
I think the motor was constantly pushed to the limits because my esup weights around 55kg, I have around 88kg, VESC limit is set to 6kW. I liked to push that thing to max. speed around 29km/h it was fun but only for a short period of time. Mostly I used it as a paddle assist and cruising around 10-12km/h.
The motor failed at the end of the second ride of the fourth season when I ride to the dock at full speed.


Thanks for the detailed info. Very helpful.

I don’t really know what I’m looking at but it didn’t seem to me that there was any “corrosion” involved.

What you described as use case also doesn’t sound unreasonably harsh to me. Yes you pushed it hard at times but that’s completely understandable as I can’t imagine many riders not “going for it” occasionally. :grinning:

My initial thinking when I started my build was that if I started with relatively robust components I would/should get multiple years of use from them without intermittent problems or constant concern that they might fail quickly.

3 years at that rate of use seems fair to me.

Do you intend to replace the motor with another 65161?

I’m looking for beefier/powerful motor. These motors from Freerchobby 12kW or 15kW caught my eye first but after some research and the experiences of other folks, I decided to avoid them.
I have two spare untouched AP C80100 motors 320kV. My plan is to rewind one of them to 80kV in delta config. I also have all stainless steel hardware like bearings, circlip, and shaft. Probably this will be my go-to for this season.

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Acutually the voltage and power doesn’t say anything. The only important info would be what the maximum motor current was. This defines the heat up via the internal resistance of that motor.
What did you set as limit for motor current?

From 20s down to 65V at 60A, that’s 3.9kW of power and cell voltage of 3.25, basically close to empty cell voltage at this current. This means that the power could not have reached 6kW, ever. Are you sure of these figures?

My initial thought was that the setup might have been overloaded but it should be running quite good to get 29kph while on the water. Which rpm would this be at your propeller pitch?

Based on your figures i’d guess the root cause to the motor failing is that the motor in reality isn’t actually capable of more than 3-4kW on longer term. The endturns get less cooling as they are squashed down and fixated with varnish, partly oil filling the motor would help to equalise the heat generated there.

I used 80100 for my first build, worked well but eventually i got a winding short where the phase wires are bundled up to get into the motor, this created a hotspot. I’d recommend to part the wires so that the water can cool each of them separately.

Lars is totally right. That motor is not capable of more than 3 - 3,5 kW continuous power.
I looked into VESC logs and the max. motor current was around 140A.
I never reach more than 6kW because I set this as a limit in VESC.
The weak points are the ends of the windings. Not enough cooling.
Poor heat transfer from ends of the windings. That is clear from the pictures I took of the dismantled stator. Windings in the core are fine, the ends are toasted.
Here the mineral oil helps a lot to take away the heat from windings to alu body and to the water.

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Some pictures of the prop and the inflatable E-iSUP.

Full album:

Just for clarity are you referring to the 65161 or the 80100?

65161 :slightly_smiling_face:

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So knowing what happened to the 65161 motor do you have recommendations for setting limits in VESC to prolong the life, what you would do differently?

It seems flipsky did a surprisingly good job of filling the slots with copper, one of the best i’ve seen, at least when judged only by the pictures. Is it like this in reality also?

Yes, it was that densely packed. It was hard to get out the windings from its slots.
I don’t understand how they wound the stator in the factory. It might be individually threaded through in each slot with a wire bundle?
The slots are completely closed, ends have a glass fiber isolator ring with trough holes for windings.
I’m still thinking about how to rewind the motor. Which type of winding technique to use?