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Discussions Question and Answer Forums Electric Scooter, Bike, and Go Kart Repair Forum

Low light comes on and breaker tripps.

I have a 2nd hand e300 that's not running right. Even with brand new and charged batteries the yellow "low" light comes on when I twist the handle past the middle and then in 20 seconds the breaker trips. It is version 20 and I've been reading that's supposed to have a single speed throttle, yet it has 2 speeds. Please advise where to start testing. I am 70kg and even the slightest incline is a great obstacle for the scooter.
From your description, we would lean towards the problem being a faulty new battery or battery pack or a faulty motor.

Since the yellow "low" battery indicator light comes on past half throttle that proves that the battery pack is significantly dropping Voltage under load. If the problem is the batteries and the circuit breaker is tripping then the circuit breaker may be worn out and need replacement also.

The first test we recommend performing is to test the Voltage of the individual batteries when the throttle is in the full position and the scooter is being held still. If both of the batteries have an equal Voltage drop that is a good sign, however, they should not drop under 11 Volts each during this test. If one of the batteries drops more Voltage than the other battery then that battery is most likely defective and may be causing the problem.

Please let us know how it goes.
I will test that asap. How can I verify the throttle and controller belong together?

Update :

Frame is version 20, charger is 24 and I can not identify the version of ECM and throttle.

The controller's model is zk2430hb4-fs. It has a 4 pin throttle connector with yellow, red, green and black wires.

The throttle is variable with 5 wires, 2 of which are black and go into the same pin in a 4 pin connector. Wire colors are 2 black, red,green and orange.

Are those two supposed to be used together?

I measured the voltage at full throttle when being held-23.5V and yellow light stays off. Both batteries perform identical when measured separately.

However when riding it drops to about 21.3 and the low light comes on under 23V.

My charger provides 27.7V when hooked to a voltmeter and 26V when charging the batteries. They are rated to be charged at 14.4-14.7V each. Is it possible I need a couple of volts more to fully charge the batteries and have the voltage stay above 23 when riding?


As to the breaker issue I replaced it with a 30A fuse and it hasn't gone off yet. Is 30 too much?

The throttle and controller are compatible with each other.

The output Voltage of the charger is within specifications for the E300 scooter. From your diagnosis, the battery pack shows as being old or worn out and needs to be replaced.


Razor engineered the E300 scooter to have a 20 Amp circuit breaker. Installing a 30 Amp fuse could cause problems due to the wiring not being able to handle that much current. A 30 Amp fuse could also put the speed controller at risk of overheating if the scooter is used to go up hills because the 20 Amp circuit breaker is supposed to trip under these type of conditions and a 30 Amp fuse would not blow at the same current level as a 20 Amp circuit breaker.

Thank you. I bought a 28.8V charger and it is much better. The low light only comes in later in the run. I also put in a 20A fuse and that has been fine so far.

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