I'm still using my home-built bike which has a secondhand 180w brushed hub motor, three new motorbike batteries and a 36v 500w controller with Hall-effect twist grip throttle bought on Ebay from someone called e-crazyman in Hong Kong. The set-up has impressed people who have ridden it, although it would not win any prizes for looks. A bonus in some ways because that deters the many local bike thieves. The batteries are charged after every use and are still in good nick.
On the day, the bike began to judder and the power dropped off dramatically, hence the long pedal home. I first suspected the motor brushes but these look ok. I connected the motor directly to the battery (off the bike) and it whizzed round. So fast, in fact, that it nearly tore itself from the jig.
I emailed e-crazyman (not expecting much because the gear was purchased over a year ago) and, in fairness, received an immediate response. He told me to test between the red and black wires of the throttle connector. I did, and obtained a reading of 5.7v. I informed him of this but have yet to receive a reply, so I don't know if this is normal or not. I am not familiar with the electronics side of things although I have some electrical knowledge. I have no diagrams for this unit so I don't know how to test the components correctly. I don't even know how the throttle works - or the controller, if I'm honest! Oh, and I also get a reading of 37v on the indicator connector when the battery is fully charged. I suspect that many controllers of this type work in a similar way as most of the ones advertised seem to have the same connections - battery, throttle, isolator, indicator, brake, etc. - so I need to know what readings to expect.
One thing that has always puzzled me is that I get a spark when connecting the battery after charging even though I have installed an on/off switch on the controller. This tells me that there is a closed circuit somewhere in the set-up. I, therefore, disconnect the battery when I park for any time to save power.
Once I find the faulty component I can order a replacement and rest my weary legs again.
Hope this is helpful to you in helping me,