G (not) Runner - hub motor wont freewheel

[BikeLoveSpreads]

Hello
I am very new to this forum. I have lurked a bitin the past when deciding how to go about creating my own electric bicycle (still a dream). I recently took on the task of helping a friend try to resurect an electric bicycle that has recently stopped working. I'm good with bikes and basic electrics but i know nothing about electric bikes. It did not take me long to become a bit stumped, so thanks in advance for any tips.

The bike is branded "G-Runner" and appears to be Chinese made and imported to New Zealand. It is a stepover style frame with a hubmotor mounted in a 22" rear wheel. It has nothing in the way of a manufacturers plate or stamp on the motor that i can see. No manual. It runs on 4-12V batteries. Very cheaply made, it seems, but also very useful as inexpensive transport for its owners who are trying to make do with little in the way of cash flow.

Without the batteries charged there was heavy resistance in the motor when pedalling. After hooking up 48 V of freshly charged batteries, the lights in the indicator panel come on, but the motor would not respond to the (twist) throttle and/or to pedalling, and there was still heavy resistance in the motor when turning the pedals. I pulled out what i think was the controller and after checking all of the connections, i focused on the bundle of wires that connects the controller to the hub motor. In this bundle their are 3 heavier guage wires (yellow, blue and green) with individual connectors and 5-7 lighter guage wires collected in one connector. I discovered that when i opened the connectors of the heavier green, blue and yellow wires, the resistance to pedalling in the hub motor disapeared. My inclination was to put some power directly into the motor via these green, blue and yellow leads, however with no wiring diagram and no experience i thought best to wait on this.

So i went away to try and find some more information and ended up here. I greatly appreciate any kind of a steer I can get.

thanks heaps

Chris

 

[d8veh]

You cannot put power to the three phase wires (thick yellow, blue, green). It's a three phase motor and can only be powered by timed pulses from the controller. Havy resistance with the phase wires connected means that the motor is acting as a generator. If the bike has regen function operated by the brakes, maybe a brake switch is stuck on, in which case the motor power will be disabled as well. First check that the brake levers spring back fully, then follow the wires to the controller. Try disconnecting the connectors at the controller end to see if that solves it. A photo of the bike and the controller would help.

 

[dogman dan]

Typicaly, if you have heavy resistance on a direct drive motor when the motor is plugged in, then the resistance goes away if you unplug the motor from the controller, that indicates a blow fet in the controller is shorting the phases.

Bet you need a new controller, or repair to the controller if you are up to it.

Once you get started trying to fix broken ebikes, a 30 buck motor controller and throttle tester is a real time saver. If you confirm all work, then it's on to the battery or just wiring issues.

 

[dnmun]

you can test the controller for shorts with a voltmeter. if you don't have a voltmeter, go find one. don't do anything else to make it work until you have a voltmeter to measure first.