Another early failure

[walkera]

Hello,

I've had my kit for about three months now.  After initial assembly, it worked great.  However, after about 100km total usage, the motor developed a problem.  Normally, you'd think if the system failed, you could simply pedal home.  This particular failure mode had me pedaling in the lowest gear in order to get down a hill at 1/5 the speed I usually go down this hill.

I contacted Golden Motor and after some initial help with wiring, it appears that there's a short within the motor itself.  After getting that far, I've heard nothing from Golden Motor for two weeks.  I guess I'm stuck trying to figure out how to get this functioning again.  In the meantime, this can serve as another datapoint for anyone making a purchase decision.  I wasn't aware there was a failure mode that could leave me stranded as well as out several hundred dollars.

[Hardcore]

what motor did you bought?

greetz

[walkera]

what motor did you bought?

greetz

I had ordered the 36v 750w motor.  From the labeling on the motor, it appears to be a 48v 1000w motor.

[wheelguy]

I saw another post that said to disconnect power from the motor (unplug, or switch if you built one in) in order to get the motor spinning freely again. Your post didn't say specifically, so I'm wondering if you have tried this? Guessing that maybe you did try this, and the motor still offers resistance, which is why you concluded it must be an "internal short".

Also wondering if you are using a 48 volt battery? If so, then the controller will deliver up to 48*40 = 1920 watts to a motor that is only rated for 1000 watts. Guess that is ok for short distances, but may burn out the winding if done for extended periods. Have you experienced using full throttle for long periods of time on most of your trips?

[walkera]

I saw another post that said to disconnect power from the motor (unplug, or switch if you built one in) in order to get the motor spinning freely again. Your post didn't say specifically, so I'm wondering if you have tried this? Guessing that maybe you did try this, and the motor still offers resistance, which is why you concluded it must be an "internal short".

That's correct.  When riding home, I disconnected the battery and it was still offering resistance.  After getting home and completely disconnecting it, again, resistance.

Also wondering if you are using a 48 volt battery? If so, then the controller will deliver up to 48*40 = 1920 watts to a motor that is only rated for 1000 watts. Guess that is ok for short distances, but may burn out the winding if done for extended periods. Have you experienced using full throttle for long periods of time on most of your trips?

48V motor, 36V controller and battery.  I've seen no issues with full throttle on long runs, but on the ride it failed, I was not using full throttle and it had not run for more than 30 seconds at a burst.  In fact, it did not perceptively fail under power - I'd used it for a small residential block or two gong uphill, then cut the throttle.  After a short distance, I tried applying power again, and got nothing.  Somewhat later (but within a minute or so), the resistance kicked in.  That's my best recollection of what happened.

[Perbear]

I saw another post that said to disconnect power from the motor (unplug, or switch if you built one in) in order to get the motor spinning freely again. Your post didn't say specifically, so I'm wondering if you have tried this? Guessing that maybe you did try this, and the motor still offers resistance, which is why you concluded it must be an "internal short".

That's correct.  When riding home, I disconnected the battery and it was still offering resistance.  After getting home and completely disconnecting it, again, resistance.

If you have high resistance after disconnecting AND insulating motor wires Two things you can do:

1) Measure resistance between ground/frame and the three motor wires, make sure the two wires not in use are fully insulated. If you have less than many Megaohms then you likely have a short to ground, and the motor wire the lowest resistance is the culprit.

2) Measure resistance, or better, inductance, between the motor wires (three combinations). If one measurement seems much lower than the others, then you have a short internal to a single coil.

If you have a short it is often fully repairable, depending on the level of heat generated during failure mode. Dismantling the motor (see instructions elswere) is not difficult and careful examination will often reveal the cause of the short.





 
 

[wheelguy]

...48V motor, 36V controller and battery.  I've seen no issues with full throttle on long runs, but on the ride it failed, I was not using full throttle and it had not run for more than 30 seconds at a burst....

Interesting - burnout due to load is certainly a possiblity that we all need to watch out for - even with the 36V controller and battery. Here's the reason...
36v controller can push 36v * 50a = 1800 watts - well over the 1000 watt motor's design limit
36v battery can deliver 36v * 30-60a = 2160 watts maximum, 1080 watts continuous for the 16AH version

Best guess is that the motor has been slowly cooking, and finally burned through its insulation at a single point. A very common problem with motors of all kinds that are regularly run near the top of their fabrication limits. Sure sounds like your conclusion is right to me - perhaps the 1000w motor just can't tolerate running hot long term.

[walkera]

2) Measure resistance, or better, inductance, between the motor wires (three combinations). If one measurement seems much lower than the others, then you have a short internal to a single coil.

This measurement I have already done.  All three combinations measure very close to 0 ohms as far as my crappy multimeter reports.  I suppose the next step is figuring out how to take the motor apart to investigate further.

[e-lmer]

36v controller can push 36v * 50a = 1800 watts - well over the 1000 watt motor's design limit
36v battery can deliver 36v * 30-60a = 2160 watts maximum, 1080 watts continuous for the 16AH version

I am not sure about your numbers here.  Yes, that 50AMP rating is the max continuous
discharge rate for A 20AH LiFePO4 battery (at 2.5C discharge rate.), but that doesn't
mean that the controller will draw that.

In fact, the fuse that comes with the 1000W 48V kit is only 20A
(1kW / 48V = 20A), so unless you are blowing fuses all the time you are not
continuously drawing more than that.

I'm no engineer, but I do have the striped hat.

Elmer

[Perbear]

I'm no engineer, but I do have the striped hat.

Elmer

Is that a hard hat? 

[walkera]

To close the loop, for anyone interested, I took the motor to a local shop with experience with other electric motors, and they determined it was actually the controller that burnt out.  The replacement controller works fine.

For anyone else with a burnt out controller, I offer http://www.mcmaster.com/#triangle-screwdriver-bits/=2riy4a

I haven't ordered them yet, so I'm not sure which size works best for the screws in the controller.  When I figure out which bit works, I'll follow up.

[Hyena]

I think you misinterpreted what Perbear said above. You have to disconnect the MOTOR wires, ie the thick yellow, blue and green wires and that will tell you if the short is in the motor or the controller. If the motor can rotate freely with the controller disconnected then the short is in the controller.

My older controller has standard phillips head screws, was yours one of the new mini cruise controllers ?