Help! Giant Twist Esprit Troubleshooting Needed

[Namastebuzz]

Hello.

I've had my mum's old ebike in the workshop for the last few years. We used it a couple of years ago for a few months and it worked OK. Last year I tried it out and the display would come on and then cut out after a few seconds so I thought it was a problem with the battery. Put it back and left it as we didn't really have any need for it TBH and I have a lot of other stuff to fix anyway (well, too much really).

So, finally decided to try it out again as our oldest could commute to the station on it and my wife could also use it for work occasionally. It has two 36v 8A batteries which I assumed were dud. Took both apart and measured the cell voltages. One battery showed 26V and all the cells showed around 2.6V. THe second battery showed 39V and all 10 cells showed 3.9V apiece so no bad cells in either. I charged both batteries up and they both went to 41.something Volts and seem to hold it allright.

Then I checked the Control/Display unit and realised it had A BATTERY in it! I thought it would be powered off the main unit but, obviously, it needs memory backup. Changed that and the system powers up fine. THe battery gauge reads full and the display does everything you ask.

The front wheel had a damaged tyre valve so I took it off (bit of a palava) and fitted a new tube. Whilst the wheel was off I inspected all the wires going into the motor and they seemed fine. There was an extra, smaller gauge, black wire coming out of the motor that was a couple of inches long and didn't go anywhwere but it wasn't cut or torn because the end was neatly finished and the core was down inside the sheath out of harm's way.

Anyway, went for a test ride and there is no assist. The motor is not coming on. Switched between all the modes and nothing. The bike pedals fine though.

So, where do I start? The brakes have no wiring at all going to them - just the brake cables - so I assume there's no possibility of brake inhibitors? I guess the next step is the sensors that tell you the cranks are turning? IS there anything else I've missed? THe wires to the motor look hard to access - I thought it'd be a plug but it's not. Where is the brain/controller/ESC located? I guess I can check power input/output there. Are there any tech manuals for these things?

Sorry for all the questions. I'm a total ebike n00b but I was a bicycle mechanic for a while and I build Brushless RC cars so I've got some relevant knowledge to be helping me along.

 

[Nealh]

Having removed the front hub motor wheel have you checked the motor connector has been fully pushed back together properly all the way ?

 

[vfr400]

What you wrote isn't very clear. When you took off the wheel, did you disconnect anything or did you leave it hanging by the motor cable?

My thoughts are that there must be a connector because the cable runs through the frame. If you can't see one, it might be just inside where the wire goes in, so you can pull it out. maybe you tugged it a bit so it's not connected.

Unfortunately, you've taken the photo from the very worst angle. it doesn't show the motor cable, nor the controller, nor which motor connection system you have.

 

[Namastebuzz]

Thanks guys.

I didn't unplug the motor cable but simply loosened it from the clips down the fork leg and swung the wheel out.

I'll go up and down the bike and check for any connectors that I can see and clean them and check they're all tight and get some more pics too.

 

[Namastebuzz]

OK I've attempted to trace the motor cable connections. It looks (to me) that the wires go right into the hub motor and there's no obvious connector. There's a rubber surround/grommet but I'm wary of prising that out unless it's meant to be removed.

I can pull several inches of cable out of the frame and the covered black cable gives way to three uncovered wires but I can't get it any further to see if there's a connector.

I opened the cover over the top of the rear rack to expose the ESC and a load of connectors. They were all clean, dry and shiny but I sprayed contact cleaner on them all for good measure.

 

[Namastebuzz]

OK. Managed to loosen the cables at the ESC end enough to give me some slack. Got the connector out of the frame. In fine condition.

Measured the voltage coming to it as 0.06V whether I'm turning the pedals or not.

 

[vfr400]

OK. Managed to loosen the cables at the ESC end enough to give me some slack. Got the connector out of the frame. In fine condition.

Measured the voltage coming to it as 0.06V whether I'm turning the pedals or not. View attachment 38103

The motor is 3 phase AC, so you have to set your meter to ACV to see anything. Even then, the controller, takes feedback from the motor about it's rotation. if it doesn't see rotation, it'll stop sending power pulses while it figures out what to do.

Isn't there a separate cable to the motor for the hall sensors? That looks like a hall sensor connector at your controller, and looks like it's-the grey or dirty white wire just above the three phase connector, and it looks like it's damaged in the photo, but it's not very clear.

 

[Namastebuzz]

Well spotted VFR400. Yeah it does look a bit damaged.

So I'm guessing the hall sensor tells the ESC that the wheel's turning and if it's broken and not telling the ESC that it's turning then there will be no power sent to the motor?

 

[vfr400]

It doesn't look so bad in that photo. There's probably another connector in there, so have a look at it in case there's any obvious fault.

Whichever connector for the hall sensors that you can get at, you need to check the hall sensor function. It's probably best to do it at the controller, because that will test the whole harness.

Pull out the glue from the back of the connector so you can get your probes in. Two of the wires, probably black and red are the 5v supply. Check that first with everything switched on, then check between any ground and each of the other three wires while you turn the motor wheel backwards. They should pulse on and off with 5v as the wheel rotates.

 

[Namastebuzz]

Thanks. Will have to wait til the weekend to have a go but I'll post back then.

 

[lolo23]

Thanks. Will have to wait til the weekend to have a go but I'll post back then.

Hi there, any news with your bike issue?
I have the same bike and suddenly gave me a similar error. When I turn on the bike, the display shows low battery (the yellow light) but the motor works and turns the power off. (the bike has two batteries, both full of charge).<
Anyone with same error and hopefully the solution?
Cheers!

 

[Namastebuzz]

Must admit I've not got any further with mine yet. A bunch of other stuff seems to have got in the way.

Is the battery in your display flat?

 

[lolo23]

Yes, the display shows the battery in yellow colour (the last bar) and it turns off. It happened few times, I moved the cables in the fork and it has worked a couple of time but not anymore.
I need to open the hub motor and see what's happening there...
Do you have any tutorial or do you know how to open this motor?
Thank you for your response!

 

[Andy-Mat]

Yes, the display shows the battery in yellow colour (the last bar) and it turns off. It happened few times, I moved the cables in the fork and it has worked a couple of time but not anymore.
I need to open the hub motor and see what's happening there...
Do you have any tutorial or do you know how to open this motor?
Thank you for your response!

Have you not considered that you may have a battery/charger problem..?
That's where I would look first, with a voltmeter.
Andy

 

[Andy-Mat]

Yes, the display shows the battery in yellow colour (the last bar) and it turns off. It happened few times, I moved the cables in the fork and it has worked a couple of time but not anymore.
I need to open the hub motor and see what's happening there...
Do you have any tutorial or do you know how to open this motor?
Thank you for your response!

May I suggest that you leave the motor alone for now at least, nothing you have mentioned makes me think of motor.
My thoughts are battery, battery charger and it's fuse, and possibly controller wiring and possibly a fuse.
Motors can easily be damaged by the wrong hands and tools, and even if it was open, what are you going to look for? Motors generally have only a few Hall effect sensors inside them that might go wrong, and getting to them can be MOST difficult.
Damage to the wiring is of course a possibility, but as long as the motor wiring has not been wrenched out, IMO it is unlikely to be the motor.
As I posted before, get hold of a multi meter, learn how to use it and check the battery voltage first, as the indications you have mentioned seem to point somewhat in this direction.
Has the battery been unused for some months or longer at some point, this ages a battery quickly and it may need re-celling.
If the battery is low, then check the output voltage of the charger using the meter.
If you told me the nominal battery voltage, boz´th I and many others here could tell you exactly what to look for.
Do make sure that you do not cause shorts or use a current meter setting, only DC voltage settings should be used to check both battery and charger.
Insulating the metal parts of the probes with insulation tape, except for the pointy end, is always a good idea.
Do wear safety glasses.
Let us know how you get on.
Andy

 

[Nealh]

Rarely does the hub motor present an issue unless the halls have been compromised.
In both cases some simple phase and hall testing can rule out faults.

In the Op post having done the above tests, pedal sensor would be my next check and test.


With the second issue.
The fact that moving wires made the hub turn lends it self to being a wire issue, either a bad hub connection or a broken wire inside the sheathing. Continuity checking those wires may be the way forward.

As we know from experience trying to give advice from a far is never always accurate, often info has been omitted by the poster or they haven't a clue how to use a meter for testing.

 

[lolo23]

Thank you so much for your response and advice Andy and Nealh!
I am going to get a multimeter and learn how to use it.
I will keep posted here in case it's useful for someone else.
Cheers!