Question about a motor and if it may be bad

[peonyu]

So here is the issue i am having...I have a Razor electric scooter that i ride at times and lately, the scooter is losing voltage very fast and then it runs at a crawl. It should run for 40 minutes @ about 15mph, but instead it hits 10mph and lasts only 10 minutes.

This has been something that i have been trying to resolve off and on for about 2 weeks now.

I have swapped out the batteries and the problem is still there, and i even ran the motor directly off the batteries to bypass the throttle and any switches / circuit breakers - didn't change anything and the problem persists.

So that leaves me with the motor. I tested the positive and negative wire leds coming from the motor with a volt-meter set to the Ohms setting, and it zeroed out on me...I am not a pro with motors, but i am pretty sure that that should have infinite resistance meaning that the motor is faulty. I think that this is the issue but i would like a second opinion before i order a new motor.

The motor btw, is just a 24v DC motor that has a sprocket on the end and the pos / negative wire leds coming from it.

 

[Paperdoc]

If the test you did was to connect the Ohmmeter to the two wires coming from the motor and measure the motor's resistance, the "zero" reading is normal. In actual fact, the DC resistance of the motor is not zero but so VERY low that many meters cannot read it properly. When a motor really is operating, what limits the current it draws is NOT simple DC resistance, it is the inductive Reactance of the motor coils. That is, as the motor rotor turns in the magnetic fields, that action produces what's called a "back-EMF", which is effectively a voltage opposing the supplied voltage from the battery. When the motor is NOT turning (as when you tried your resistance measurement) there is no "back-EMF", and the windings of the motor are heavy enough to behave like a VERY small DC resistance.

Testing whether a motor like that (or maybe some other part of your scooter) has a flaw is more complicated and you really should take it to a competent service tech to determine your problem. What you've done so far is eliminate the simple explanations, so now comes the tricky part.

 

[peonyu]

You are right, i hooked up the multi meter to the motor again and spun the shaft and it gave me a 1 instead of a 0 for continuity. I guess it is time to take it to the shop and see what they say, i was hoping it would be a easy problem to isolate / bad motor but doesn't seem that way.

 

[Paperdoc]

Good luck. We'll be interested to know how this goes.

 

[deadlyapp]

Unfortunately you may find that it is just cheaper/easier to replace the motor completely. I had a 1HP fan motor that I wanted to have looked at / serviced and nobody was really willing to spend the time to do it considering a new replacement was only $250.