Motor noise with upgrade.

flyn2low

Hey y'all I have recently upgraded my 99 EXGO TXT with an Alltrax XCT500 48V controller and a high torque motor from ScottyB. Everything is perfect except for when accelerating or decelerating from 6-11mph there is a sound almost like marbles knocking around from the motor area. I have loaded a new field map hoping that would resolve it but it hasn't. The wired part is when decelerating through that mph range if you switch the key off the sound goes away.

Any ideas?

BGW

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yamahaguy97

hmm wow marbles?? i can't really say its brushes because i doubt you would be able to drive it. that's strange, when you switch the key off it goes away??

BobBoyce

I guess unpowered marbles are quieter

Doesn't this sound like a slight motor alignment issue causing a slight bind at the spline that only shows up under torque in either direction?

MillwrightMike

That's crazy! Until reading this is forgot about the field map update last week. My cart is now doing the same thing. I doubt it has anything to do with it but I'm not much of a cart expert. I have an 06 ezgo txt pds with a growling noise coming from the motor area as well.

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JohnnieB

My sepex motor whines rather than rattles like there is marbles in it, but the sound of the loose marbles in my head may be overriding the marble sound elsewhere. Anyway, the sound is most likely armature current related and turning off the key interrupts the normal path for regen braking current.

Hopefully, you have the 6A Regen braking diode installed across the solenoid's big terminal, so you don't over-volt the XCT controller when you power it down while the cart is moving.

flyn2low

Yes key off noise goes away.

So no danger of damage to the motor with the sound? If I reduced all the region braking values to 0 do you think the sound would go away? Yes I have the 6A diode. How would you over volt the controller if you de-engergize the whole thing by switching KO?

JohnnieB

1. I don't know for sure, but probably not.

2. Maybe, but only when decelerating.

3.

4. You only place the XCT controller in standby when you switch off the key, which in turn de-energizes the solenoid.

If the cart is still moving, the motor is still acting as a generator due to residual magnetism and producing voltage. The solenoid contacts are now open, so there is no current drain on the electrical energy being produced by the motor and the voltage skyrockets. The voltage the motor acting as a generator impinges on the controller terminals can exceed 100V (depending on cart speed), which can take out the MOSFETs as well as some other stuff.

This isn't an issue with controllers that use a pre-charge resistor to keep the filter capacitors inside the controller charged because opening the solenoid contacts didn't completely disconnect the battery pack from the motor and the voltage generated by the motor acting as a generator was clamped to the battery pack voltage, more or less.

The XCT charges the filter caps via J1 Pin-4 or Pin-5 (Pin-5 most likely) and doesn't use a pre-charge resistor, so it needs a steering diode to provide a current path for regen voltage/current when the solenoid contacts are open.

flyn2low

Makes sense. Thanks for the education I will refrain from turning the key off! My luck it will cause some unrelated catastrophic failure like a wheel falling off.

Alright time to muddy the water. Set all regen values to 0 and it still makes the noise??

Is it possible that it could be mechanical noise from the rear end? If so why does the noise go away when switched off?

JohnnieB

Setting the Regen levels to zero in the controller doesn't completely stop the motor from acting as a generator, it just stops it the regen current from being forwarded to the battery pack. The faces of the gear teeth that touch change sides when accelerating and deceleration the same as they do going forward vs reverse, and when you shut the key off, the intensity of the mechanical force on the gear faces changes. Other than that, I have no idea why the sound goes away.

I've had a clunking sound in my differential when decelerating ever since I exploded my stock PDS motor and slid to a stop from 30+MPH. Or at least, I first noticed it after I replaced the motor and the controller it took with it. I thought it was the motor at first, since I could hear it when I pushed the cart with the motor installed and could hear it without the motor installed, but D&D tested it and gave it a clean bill of health.

The only thing I've been able to find in the differential, hubs and axles that is the least bit suspicious is some visible wear on the input gear. Since I couldn't pinpoint what was making the noise, I decided to run it until whatever was broke so I could find it.

That was three years age, the noise is still there and cart is still going strong.

cgtech

did your new motor have the rubber bumper in the motor coupler? if the sound is new with the new motor, i think i would start by checking that there is proper tension between the bumper & input shaft. proper tension is a very small gap between the motor and axle housing that is closed as the bolts are tightened.