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E300: Bad Controller or Battery?

Hello, I recently picked up a used E300 for pretty cheap and I'm trying to diagnose what's wrong. Here's where I'm at:

* Controller "clicks" when applying throttle. It sounds like it's clicking on, then off right away.

* I assumed the battery was bad, but individually they both test out at about 12.6 volts and when I attach them directly to the motor the voltage doesn't drop below 12.

* Break switch tests fine

* bypassed fuse, switch etc.

My gut tells me it's probably just bad batteries, but I can't get over the fact that the volts don't really drop when under load. Which should I replace first, the batteries or controller? Any other ideas?


The motor will not place very much load on the batteries if the rear wheel is spinning in the air. When the batteries were attached directly to the motor for load testing was the brake applied or wheel dragged on the ground to put a heavy load on the motor?

Ah, that's an interesting point. Yes, the wheels were spinning freely when I connected directly so that might explain the lack of voltage drop. That said, the wheels were also spinning freely when I applied throttle through the controller and all I hear is the click. Wouldn't the lack of resistance mean that too should have worked?

Yes, I agree that with the 12 Volts per battery reading if the controller and throttle were good it should have worked with the wheels off the ground. It would be a good idea load test the batteries anyways though just to make sure they are good before replacing the speed controller and or throttle.

This is very helpful. I'll give this a shot and report back.

For some reason I thought you had a Crazy Cart instead of E300 so the testing directions I posted (and now deleted) were wrong for the E300. There are so many versions of the E300 that I can not post throtle testing directions without knowing which version it is. Do you know which version the E300 scooter is?


The E300 label indicates 31. Or do you need the version of the controller?
The scooter version is fine. The E300 version 31 scooter has a simple on/off throttle with two momentary switch contacts inside of it. To test the throttle unplug it from the controller and check for continuity between the two orange wires, and then again between the two brown wires. The same color wires should have continuity when the throttle is in the full throttle position, and not have continuity when the throttle is at the zero throttle position.

Thanks, I'll test that. However, since I can clearly hear the clicking in the controller when applying the throttle, doesn't that indicate the throttle switch works? Or is it possible the switch is immediately switching off? I suppose I could also jumper the two orange wires to force full throttle?

The throttle has two switches inside of it so if the controller clicks then one of the switches could be good and the other bad. The throttle wires could be jumpered on the controller's throttle connector to simulate a working throttle. I would turn the power switch on before jumping the throttle wires though because the controller might have a safety feature that does not run the motor if it detects the throttle on when the power switch is turned on.

I'm so confused! I did a continuity test on both of the switch wires and they seem to react properly to the throttle so at this point I assumed it was the battery. I tried with known working batteries both testing out at 13.2 volts and it's the exact same problem. Can I assume my controller is bad now?

We would test a few other parts before pointing toward the controller as the problem.

Since the throttle and battery pack have already been tested and are good we will leave them off of the list.

  • Test for input Voltage at the controller. (This will determine if the wiring harness, fuse, and switch are good)
  • Unplug the brake lever from the controller and see if the scooter runs with it unplugged. If the scooter does not run with the brake lever unplugged then bridge together the controller's brake switch connector terminals and see if the scooter runs then. (Some versions have normally open brake switches and others have normally closed brake switches so this test will simulate a good brake switch for all versions)
  • Test the motor by unplugging it from the controller and wiring directly to a battery or battery pack to make sure that it works.

After these tests have been performed and if none of the tests point toward a faulty part that is connected to the controller then we would presume that the controller is not working.

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