July 24, 20196 yr 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
July 24, 20196 yr 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.
July 24, 20196 yr Author 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
July 24, 20196 yr 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?
July 25, 20196 yr Author 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
July 25, 20196 yr 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.
July 25, 20196 yr Author 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
July 25, 20196 yr 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?
July 25, 20196 yr Author 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
July 25, 20196 yr 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
July 25, 20196 yr 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.
July 26, 20196 yr 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
July 26, 20196 yr Author 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
July 26, 20196 yr Author 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
July 26, 20196 yr 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. Edited July 26, 20196 yr by Nealh
July 26, 20196 yr 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.)
July 26, 20196 yr 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.
July 26, 20196 yr 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?
July 26, 20196 yr Is that a characteristic of the particular motor used on the Wisper 806SE? So badass type dongles aren't effective on the 806SE? It's a typical characteristic of many electric bikes. Why would you want a Badass dongle on a Wisper when you can derestrict it for nothing? Dongles of any type have no effect on current or power. They only interfere with the speed signal to fool the controller into releasing the speed limit.
July 26, 20196 yr It's a typical characteristic of many electric bikes. Why would you want a Badass dongle on a Wisper when you can derestrict it for nothing? Dongles of any type have no effect on current or power. They only interfere with the speed signal to fool the controller into releasing the speed limit. Let me put that another way - since Badass dongles work with Bosch, Brose, Continental, Fazua, Giant, Kalkhoff(Impulse), Panasonic, Pendix, Shimano, Specialized and Yamaha motors am I right in thinking that these motors don't exhibit your typical characteristics? Do you know for sure that Wisper 806SE motors exhibit your typical characteristics? I'm just surprised that the back EMF has such a big effect at such low cycle speeds.
July 27, 20196 yr Let me put that another way - since Badass dongles work with Bosch, Brose, Continental, Fazua, Giant, Kalkhoff(Impulse), Panasonic, Pendix, Shimano, Specialized and Yamaha motors am I right in thinking that these motors don't exhibit your typical characteristics? Do you know for sure that Wisper 806SE motors exhibit your typical characteristics? I'm just surprised that the back EMF has such a big effect at such low cycle speeds. I'm not sure what your point is or what your question is. Ask it again from first principles. I think you've got completely mixed up. Back emf has no effect at zero speed, small effect at low speed and big effect at high speed. It's the thing that limits every electric motor to a maximum speed. The amount of back emf depends on the motor's KV, which is how many rpm it takes to generate 1 volt. When you choose a hub-motor for an electric bike the KV is a very important characteristic. If it's too low, the bike won't reach 15 mph. If it's too high, the motor will be inefficient and overheat. The ideal for a legal bike is somewhere around 7.2 for a 36v battery, which will mean that the motor will generate 36v at 260 rpm and give maximum power (not torque) at around 15 mph. That's why I say 260 rpm is typical for OEM bikes. It's basic good design. The same characteristics affect crank motors, but instead of bike speed, it's crank speed they have to get right. If they choose a KV too low, the motor will max out and produce no power at a normal cadence. Too high will make the motor run inefficiently. The problem here is that people have different cadences. Some prefer a low cadence of 60 or less and some prefer closer to a 100. Unfortunately, there's no solution to that other than make sure you knowthe characteristics of the motor in the bike you're buying
July 27, 20196 yr I'm not sure what your point is or what your question is. Ask it again from first principles. Let me try for the 3rd time: You said "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. " and "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." What is the maximum speed you could get out of your typical bike, even with a dongle or speed restriction otherwise disabled, before the back EMF results in zero current flowing (ie zero assistance being available), 14mph seems very low?
July 27, 20196 yr When you choose a hub-motor for an electric bike the KV is a very important characteristic. If it's too low, the bike won't reach 15 mph. If it's too high, the motor will be inefficient and overheat. The ideal for a legal bike is somewhere around 7.2 for a 36v battery, which will mean that the motor will generate 36v at 260 rpm and give maximum power (not torque) at around 15 mph. That's why I say 260 rpm is typical for OEM bikes. It's basic good design. A motor's "KV" rating it is the number of revolutions per minute that the it will turn when one volt is applied under no load conditions. So with 36V applied to it, a motor with a KV of 7.2 will produce 259.2 rpm under no load conditions. The paragraph I've quoted makes no sense whatsoever to me.
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.