500w brushed speed controller lost almost all power

[Adamsmashem]

I have a custom razor E300 scooter, with a 8s4p lifpo4 battery (24v, 20ah), a 500W motor, and a 500w variable speed controller. After putting a hefty load on my scooter (2 people on it, going uphill for awhile) it starting loosing power fast, to the point where the wheel will only spin if it is off the ground. I have confirmed that the battery and motor are both completely fine. It has to be the speed controller. Does anyone know why it did this? Im hoping to fix this instead of buying a new one. Also, I dont want this happening again, Ive put my original speed controller through alot worse, and I want to be able to do the same. I havent opened it up yet, but no melted wires, or any smell after opening it an hour later.

 

[Chalo]

There is the possibility that you cooked the magnets in your hub motor. That would cause the motor to spin abnormally fast, but with greatly reduced torque. If that's the problem, it's unrelated to your controller.

 

[Adamsmashem]

There is the possibility that you cooked the magnets in your hub motor. That would cause the motor to spin abnormally fast, but with greatly reduced torque. If that's the problem, it's unrelated to your controller.

Im not using a hub motor, im using a brushed one, and using the original speed controller the motor works just fine

 

[Chalo]

Im not using a hub motor, im using a brushed one, and using the original speed controller the motor works just fine

Well then it looks like you found your problem. Maybe you fried one of your three phases and the controller is limping along on the other two.

 

[Adamsmashem]

Well then it looks like you found your problem. Maybe you fried one of your three phases and the controller is limping along on the other two.

I believe the three phases are only for a brushless motor, mine is brushed. Theres only a + and - for the output of the speed controller

 

[Chalo]

I believe the three phases are only for a brushless motor, mine is brushed. Theres only a + and - for the output of the speed controller

Ah. Well at least brushed DC motor controllers are cheap as dirt.

 

[amberwolf]

Brushed controllers usually fail either completely (no motor power at all) or shorted (stuck on, no throttle control).

I haven't seen one fail the way your symptoms imply, but since the likely problem would be overheating inside the controller (if your motor did not overheat), that could cause damage to various components. If solder melted on current-monitoring shunts (if any***), and there were multiple in parallel, it could have disconnected some of them, causing the reading from the remainder to indicate higher current than actual, so the controller wouldn't be allowed to operate the motor at the normal power level. Or it could have damaged capacitors, which would have different effects depending on what each one is intended to do. Same with active electronic parts. FETs could be damaged so they have far higher resistance and be unable to deliver current as intended, etc. Could even just be a connector/wire fault form heating, etc.

You could investigate to see what the controller is actually doing under load and offground to see what difference in operation you find, and that will help point to the fault. Not sure if just a multimeter would be enough or if you'd need an oscilloscope.