Low RPM cogging/growling on Dual Motor Offroad EV Setup

[Mark199]

Hey Endless-Sphere Crew,

After spending many hours crawling through the forums to try and find our answer, finally taking the time to post this up to see if anyone can help point us in the right direction.

My brother and I are creating an offroad micro EV to be used around property. We have some issues getting the settings of the controller's right though.

The cart is epic, drives like a beast and climbs hills no worries. We have a huge piece of natural bushland and tracks to put it through its paces.

Main Issue:
- At VERY low rpm the hub motors hesitate to start, sometimes reversing first before finding forwards, then makes a cogging/growling sound until it picks up speed. Listen/see here:

(This noise does NOT go away when we turn off REGEN) (RLS_TPS BRK % =0)

- With cart switched on, but no throttle applied, when we turn the wheel by hand, it randomly "cogs"/gets stuck at points, and we can feel the regen seeming to try and kick in. Listen/see here:

(This noise goes away if we switch off REGEN) (RLS_TPS BRK % =0)

- When we drive the cart at low speed, the regen doesn't seem to kick in until the cart is at a certain speed, then it works well. Seems to have almost no regen at low speeds though. If we drive fast, the regen kicks in beautifully and slows the cart down no worries.

- We want to be able to drive this cart around using mainly REGEN, with the physical handbrake for emergency or stopping on hills etc.

- When power switched off, the wheels spin freely with no resistance, noise or issue. So its not a mechanical issue.

EDIT: - When we first wired up the hub motor on the workbench, it did not make this cogging/grinding noise. It is only since we have changed settings and wired the two sets of controllers and hub motors to the cart that we experience this.

Setup:
- QS QS205 2000W 50H V2 48V x 2 (Rear Wheel Drive)
- SIA KLS6022H Controller x 2
- SIA CT-22 Speedometer
- SIA Throttle Pedal (No brake, REGEN only.)
- 48V Lithium
- 48v 120ah lifepo4 cells
- 250 amp BMS
- NO Brake pedal (regen Only when throttle released)
- Physical Handbrake will be installed soon.

Settings:

 

[scianiac]

I believe most of the cause of these issues is just how things work. Motors with hall sensors still need to rotate a certain amount for the halls to start working so cogging when starting under high loads can happen. And while to what extent depends somewhat on the controller design regen only works when the motor is spinning fast enough for the controller to generate a voltage higher than the battery.

The only ways to get braking at near zero or zero speed is to either short the phases which has issues so is not normally a feature on most controllers or active braking / position control which generally requieres some more precise position feedback than halls. If the controller can be configured for an encoder and you can find a place to mount one that wil solve the first issue and technically could solve the end if the controller supports servo mode but probably not and it may be to hard to setup in any way that works nicely.

As for which settigs to adjust to improve the issues somewhat I have no idea as I'm not firmilar wit these controllers but somebody may have some advise on how to improve them, particulalry the first maybe can be improved or mostly solved with settings.

 

[Mark199]

Hey Scianiac,
Thanks for the response.

When we first wired up the hub motor on the workbench, it did not make this cogging/grinding noise at low rpm. It is only since we have changed settings and wired the two sets of controllers and hub motors to the cart that we experience this. I have now made an edit to the original post to reflect this. We are pretty sure its got something to do with the settings and sadly we cannot find the original settings again. The supplier has not been very helpful on that front.

 

[fechter]

The problem sounds like what happens when the controller isn't reading the hall sensors properly or it's running in sensorless mode.

 

[Mark199]

The problem sounds like what happens when the controller isn't reading the hall sensors properly or it's running in sensorless mode.

Hey Fechter,
Thanks for your response and patience with my reply.

From what I could find online, the Kelly KLS-H controller does not have sensorless mode. We have double checked the wiring of the hall sensors and all seems like it should. The controller does has an Identification angle operation function which I am assuming takes care of ensuring the hall wires are in right order when operating after its done.

It is happening on both of the hub motors connected to the cart, each of them with their own controller. We have tried today to isolate one side, removing the second hub motor wiring, and still same issue. So assuming it is not related to interference.

We are not quite sure where to go next from here.

Do you know how to update the firmware on these KLS-H controllers? I tried the kellycontroller.com website but it seems to be errors on everything but the main homepage.

Any ideas would be greatly appreciated! We are so close to getting this done.

 

[fechter]

I get the same problem when I try to go to the Kelly website. Not sure what's up with that. Hopefully it comes back up after the weekend.

I did manage to find a copy of the manual. See attached.

Since it seems like it was working at one point, it would seem like one of the settings is off, but not sure which one. The manual explains most of the settings. It seems like maybe it's trying to brake at the same time it's supposed to be running.