How to test Motor

[Engineer]

I have an Alien Titan bought 2 months ago. Bob of alien bikes exchanged
the battery as we thought it faulty (only running for 8-9 miles and
cutting out.) I fitted the new battery but the motor would not run at
all, Bob sent a new controller which I fitted but again motor does not
run.
It is a Suzhou Bafang 24 volt motor. The fault condition is when key
switch turned on all 3 lights are on, at the bike. Also when I measure
with a multimeter each of the 3 "phase wires" going to the motor read
24 volts measured between each phase wire and -ve wire at key switch
regardless of position of throttle.
I do not fully understand how these brushless motors function but am I
to understand that only 2 of the phases should have 24 volt (one of which is -ve) on them for the motor to turn. Is there any way I can test the motor (I have another 24 volt source)?
I have visually checked the wiring for breaks and kinks as best as
possible, also I have disconnected the brake wiring.
Bob says he has never had a motor fail so I would like to be able to at
least confirm motor is ok. I do miss being able to ride the bike as
due to my age and lack of fitness, I cannot ride it without the motor.

Thanks in advance

John

 

[Andrew harvey]

motor test

To prove the motor windings, first disconnect the motor, then measure the resistance between pairs of ends, with a multimeter set to it's low ohm range. The readings should be similar, say around 0.5ohm.
The windings are wired in a star or as Crystalyte call it a Y fashion, each of the three winding cables feed a different set of coils, but the negative terminal of the coils are joined together. As they are all 'commoned up' any voltage appllied to one cable will be applied to them all, unless a return (negative ) path is made. It may be that your controller works by switching the negative line.
Of more use is to test the hall effect sensors, find the small red and black cables, going to the motor. Apply your control voltage from say your throttle, + to the red cable, - to the black, connect your multimeter, set to read low DC voltage, to the black cable and a hall effect sensor lead, normally with SB motors they are blue green and yellow. Now turn the wheel, slowly, if you have a freewheel turn it backwards.
If the sensor is good the voltage should vary between, about 0, and your control voltage, repeat this for all 3 cables. If you find one or more cables were the voltage does not change then it is likely that you have found the fault. The hall effect sensors do not normally break themselves but the cables used are prone to breaking down due to their small size and the bends in them.
You can also use a voltmeter to check there is a voltage applied to the red and black hall sensor cables.
I have used SB motors for about 5 years now and like Mr Alien have never had a motor fault, but you may still have one.
For a more complete and better written fault finding guide check out e-bike.ca there tests are for Crystayte motors but apply to most brushless motors just as well.

 

[Tsnafu]

I have an Alien Titan bought 2 months ago. Bob of alien bikes exchanged
the battery <snip> Bob sent a new controller which I fitted but again motor does not
run.

Then tell Bob you want a new wheel, it's not down to you to find out why it isn't right. You have a 1 year guarantee on all major parts (and the sale of goods act on your side)

Tom

 

[Engineer]

Thanks for comprehensive reply Andrew, I will try out your suggestions as soon as possible. As for returning the wheel, well yes the motor is under guarantee, but I would still like to positively identify the problem (it may be just a loose wire) if possible and also there is the cost and hassle with sending it back.


Thanks for replys.