Help with Kids Electric Quad 36V

[Electricquad123]

My son’s 36V quad bike has been converted to run of 2x18V drill batteries . It was all working fine until it stopped about 20 minutes into the ride, batteries still reading about 75%. Anyway re charged and now the motor /wheels run fine when I lift the back axle of the ground but as soon as it’s put back on the ground or he sits on it it doesn’t move. Output from batteries reads about 39v, input to motor 33.5v then when I pull the throttle it jumps to 39v but still no movement when under load. Could it be faulty controller or motor? Or is something more serious
Mechanically everything runs free and fine no obstructions

 

[brianmoooore]

Connect the batteries directly to the motor, bypassing the controller, and see what happens.

 

[Electricquad123]

Connect the batteries directly to the motor, bypassing the controller, and see what happens.

I did it while on the floor and the quad shot backwards , do you think this proves it’s a dodgy controller? Sorry compete novice here lol

 

[brianmoooore]

That's what it sounds like, although there's still a remote possibility that the motor is taking excess current, and the controller has electronic overload protection which was kicking in..

 

[Electricquad123]

That's what it sounds like, although there's still a remote possibility that the motor is taking excess current, and the controller has electronic overload protection which was kicking in..

Thanks for your help, is there any way to check? It seems 39v at the battery and 39v at the controller when the throttle is on full so would guess that means it’s fine? But again Ive not idea .

 

[brianmoooore]

Output from batteries reads about 39v, input to motor 33.5v then when I pull the throttle it jumps to 39v

A voltage is measured between two points, typically with a black probe and a red probe. Where did you have the probes when you took these three measurements?

 

[mainline]

Thanks for your help, is there any way to check? It seems 39v at the battery and 39v at the controller when the throttle is on full so would guess that means it’s fine? But again Ive not idea .

It more than likely has a controller that drives the motor using Pulse width modulation.
It sounds like a problem with the controller.