power problem with Wisper 806SE

[mpbarrett]

I have brought a second hand Wisper 806SE. I knew when I brought it that the battery had failed (reading less 10V..) and before buying a new Wisper battery I have tried running it on a new 36V 10A battery pack brought from Ebay. I want to decided whether I like it if I do then I will buy a new battery for the Wisper and use the new Ebay battery pack on another bike I want to try to convert.
The bikes works but seems to have strange problem. If I run it and either use the throttle or pedal assist once the current reading goes to maximum then the assist stops until the speed has dropped. This seems to happen above >13mph.If I keep the current below maximum its all fine and works.
It feels like there is a current limiter that's tripping in and then resetting.
I assumed that this must be an issue with the cheapo battery pack I am using, but the voltage from the pack does not go to zero so I don't think the battery pack itself is current limiting.
Does the control system on the Wisper itself have a current limitation that might be cutting in?
Any ideas welcome, I am new to electric bikes but have a background in electronics so am happy to play with the power system (and am very aware of the risks of playing with Li-ion batteries).
BTW the bike is very impressive, beautifully made and designed.
mike

 

[vfr400]

It's not likely to be the battery, but maybe it is because I can't understand what you mean by the current going up. Please explain.

 

[mpbarrett]

I mean the current read out on the display. The power goes (no drive) after the current reading has gone up to maximum (5/6 blobs).
regards
mike

 

[Deleted member 25121]

How low does the speed have to drop to before the motor will kick in again?

 

[vfr400]

I mean the current read out on the display. The power goes (no drive) after the current reading has gone up to maximum (5/6 blobs).
regards
mike

What I'm trying to establish is whether your problem causes the current to go up or whether your motor cuts whenever you use high current. Can you explain?

 

[Amoto65]

Could it be the display settings? ie wheel size etc....

 

[mpbarrett]

What I'm trying to establish is whether your problem causes the current to go up or whether your motor cuts whenever you use high current. Can you explain?

Sorry the motor cuts out when the current goes high as the speed increases. Usually above 13mph drive doesn't come in again until the speed has dropped.
Need to test it again to fully understand what's happening...
Thanks mike

 

[Roger Cashmore]

this description you have described of the power going quickly up and then dropping is precisely the same problem I have with my wisper. When it drops suddenly from full power to zero power it almost feels like the bike has put the brake on. It "hunts" up and down and for me usually seems to occur when pulling up a hill. It is a problem with the factory system / settings.

 

[mpbarrett]

this description you have described of the power going quickly up and then dropping is precisely the same problem I have with my wisper. When it drops suddenly from full power to zero power it almost feels like the bike has put the brake on. It "hunts" up and down and for me usually seems to occur when pulling up a hill. It is a problem with the factory system / settings.

That's interesting have you found a solution to it?
Mike

 

[vfr400]

Sorry the motor cuts out when the current goes high as the speed increases. Usually above 13mph drive doesn't come in again until the speed has dropped.
Need to test it again to fully understand what's happening...
Thanks mike

Electric bikes with hub-motors don't work like that. As the speed goes up, the current goes down due to the back emf from the motor opposing the voltage from the battery. I still can't understand from your description what you're saying is happening. Does it do it on level 1 on the LCD? Please give more detail about the circumstances.

You have a speed limit of 15mph on your bike, so the motor will be cut when you reach 15 mph and start again when your speed is below 15 mph. Is that what you're experiencing?

 

[mpbarrett]

That's not correct what you are suggesting is that as the speed increases the power (I*v) goes down that's just not possible otherwise you could reach a terminal velocity using no power...
I understand that the power will be limited at 15 mph to ensure the speed doesn't exceed the legal limit. But that is not what happens.
Above 13mph when the current display goes to maximum the drive then stops no further assistance, once the speed has reduced to less than maybe 8mph and a period of time has passed then the power comes back on again.
It feels like something is current limiting, rather like a thermal cutout that them takes a period to reset.
I will try to get some current measurement data from the system once the weather has got s bit cooler, 100f in Cambridge today.
Regards
Mike

 

[Deleted member 25121]

That's not correct what you are suggesting is that as the speed increases the power (I*v) goes down that's just not possible otherwise you could reach a terminal velocity using no power...
I understand that the power will be limited at 15 mph to ensure the speed doesn't exceed the legal limit. But that is not what happens.
Above 13mph when the current display goes to maximum the drive then stops no further assistance, once the speed has reduced to less than maybe 8mph and a period of time has passed then the power comes back on again.
It feels like something is current limiting, rather like a thermal cutout that them takes a period to reset.
I will try to get some current measurement data from the system once the weather has got s bit cooler, 100f in Cambridge today.
Regards
Mike

That shouldn't happen, something is faulty.
Above 13mph you have maximum current displayed but zero assistance, either the displayed value is wrong or current is being dumped somewhere with no motive power coming from the motor, some thoughts:
1. does the controller or motor get hot if you continue in this state for a few minutes? If so it could indicate that the current displayed is correct and the fault could be in the controller or motor
2 are you able to wire in an ammeter in series with the battery to see what the actual current is? Could be tricky but might be possible with the bike on a stand. If the real current is low under fault conditions it could indicate a likely controller fault
3 I'm thinking that it's unlikely to be a wiring problem if the fault appears and disappears at consistent speeds.

I speak as an electronics engineer with an ebike

 

[vfr400]

That's not correct what you are suggesting is that as the speed increases the power (I*v) goes down that's just not possible otherwise you could reach a terminal velocity using no power...

I've been working on electric bikes for very many years. I know how they work. I'm trying to help you. If you have the answers tell me how it works out.

 

[MikelBikel]

I have brought a second hand Wisper 806SE. I knew when I brought it that the battery had failed (reading less 10V..) and before buying a new Wisper battery I have tried running it on a new 36V 10A battery pack brought from Ebay. I want to decided whether I like it if I do then I will buy a new battery for the Wisper and use the new Ebay battery pack on another bike I want to try to convert.
The bikes works but seems to have strange problem. If I run it and either use the throttle or pedal assist once the current reading goes to maximum then the assist stops until the speed has dropped. This seems to happen above >13mph.If I keep the current below maximum its all fine and works.
It feels like there is a current limiter that's tripping in and then resetting.
I assumed that this must be an issue with the cheapo battery pack I am using, but the voltage from the pack does not go to zero so I don't think the battery pack itself is current limiting.
Does the control system on the Wisper itself have a current limitation that might be cutting in?
Any ideas welcome, I am new to electric bikes but have a background in electronics so am happy to play with the power system (and am very aware of the risks of playing with Li-ion batteries).
BTW the bike is very impressive, beautifully made and designed.
mike

I'm using an 806SE which does exactly the same thing. On Assist level5, goes to 15.5ish mph fine, then motor torque stops, speed falls to 14.4ish, and torque comes back on full suddenly, back up to 15.5ish, off, on, off.. etc. Gets annoying as it seems willing enough, and a smooth tail off would be better for riders balance/comfort, maybe for battery too. Same behavior on throttle.
Reducing assist to level4 13.?mph stops it. I assume because 15.5 limit is never exceeded (tho "to assume makes an @ss of u and me"). So seems to be a power controller speed limit issue.
Could a settings change help? If someone could tell us how the menus work or where the info is please it would be most helpful.
Cheers. Mikel

 

[mpbarrett]

I've been working on electric bikes for very many years. I know how they work. I'm trying to help you. If you have the answers tell me how it works out.

sorry I did not mean to upset you, put it down tot he heat...
mike

 

[mpbarrett]

That shouldn't happen, something is faulty.
Above 13mph you have maximum current displayed but zero assistance, either the displayed value is wrong or current is being dumped somewhere with no motive power coming from the motor, some thoughts:
1. does the controller or motor get hot if you continue in this state for a few minutes? If so it could indicate that the current displayed is correct and the fault could be in the controller or motor
2 are you able to wire in an ammeter in series with the battery to see what the actual current is? Could be tricky but might be possible with the bike on a stand. If the real current is low under fault conditions it could indicate a likely controller fault
3 I'm thinking that it's unlikely to be a wiring problem if the fault appears and disappears at consistent speeds.

I speak as an electronics engineer with an ebike

sorry I am not making myself very clear...
The when the drive cuts out the current does drops to zero.
I will set it up in the garage today and directly monitor the battery current and voltage.
I am a retired professional electronic engineer with (30 years designing and building electronic system for a oil field research company) with a very well equipped garage
Does anyone have cct diagram for the 806SE control system?

BTW thanks everyone for all the helpful comments.

regards
mike

 

[Nealh]

If the current drops to 0 then usually the target speed in this case 15.5mph has been reached. Though your reading say's 13mph have you clarified that with a GPS reading at the same time, it may be that the lcd reading is out and a LCD P1 type parameter setting needs adjustment.

 

[Deleted member 25121]

sorry I am not making myself very clear...
The when the drive cuts out the current does drops to zero.
I will set it up in the garage today and directly monitor the battery current and voltage.
I am a retired professional electronic engineer with (30 years designing and building electronic system for a oil field research company) with a very well equipped garage
Does anyone have cct diagram for the 806SE control system?

BTW thanks everyone for all the helpful comments.

regards
mike

Ah, if the current drops that changes things significantly. As MikelBikel suggests it could be the controller hitting the assistance speed limit at 13mph (not far off the legal limit of just over 15mph) but if it doesn't kick in again until you get down to 8mph, as you said earlier, then something is wrong.

Also you mentioned that a period of time must pass before the power comes back on again which suggests an overheating problem.

If I was you I wouldn't bother with the tricky current measurements for now and focus on the conditions necessary for power to be restored to the motor. Also have a look to see if the controller or motor are overheating.

(By the way, the motor is likely to be brushless with internal Hall sensors detecting the position of the permanent magnet rotor, current is applied through stationary outer coils. The controller limits the motor speed by controlling those currents.)

 

[vfr400]

The controller limits the current to a fixed amount - typically 15 amps.
When a motor is stationary, it has low resistance, so without the controller limiting the current, it would draw enough current to burn, which is why the controller limits the current.

As soon as the motor starts to turn, it generates a back emf that opposes the battery voltage. At around 260 rpm,the back emf is 42v so your motor has no net voltage, no current can flow and you have zero power.

Without the controller, the current vs speed graph would be a ramp from something very high at zero rpm down to zero at around 260 rpm. With the controller, the graph is a flat 15 amps until some point where that line meets the ramp function, then it ramps down to zero following the same ramp as without a controller.

At 14 mph, it's almost certain that you will be in the zone where the back emf is controlling the current below 15 amps, so you won't get maximum current.

All this is considering that you have set the bike to give maximum power.

If you put an ameter or wattmeter on the battery line, you will see maximum current only when the motor starts to spin. After that, it will go down to 1 amp with the wheel in the air.

If you see anything different to what I describe, something is drastically wrong. This is what I'm trying to establish with you. The exact behaviour will indicate the type of cause to your problem.

If your current is going to maximum when your controller is set to level 1, then you clearly have a problem, which would be something like a motor connector not pushed all the way in, a bad connection somewhere else in the motor cable or a faulty MOSFET in your controller.

If only you would describe the facts in detail instead of letting your incorrect preconceptions colour your minimal report, we could get to the bottom of it.

 

[Deleted member 25121]

At around 260 rpm,the back emf is 42v so your motor has no net voltage, no current can flow and you have zero power.

Is that a characteristic of the particular motor used on the Wisper 806SE?

At 14 mph, it's almost certain that you will be in the zone where the back emf is controlling the current below 15 amps, so you won't get maximum current.

So badass type dongles aren't effective on the 806SE?