Motor stops too early after going fast - but only on max power

[SimonMikkelsen]

A year ago I bought an ebike from dutch Brinckers, the dealer said the electric system is provided by Batavus. The motor is in the front wheel.
It has 9 power levels, 1-9 where 9 is max. If I go a bit past 25 km/h, like 27, the motor will kick out already at about 22 km/h when I am in power level 9. If I change to 8 (which is lower power) it will work just fine, but of cause it only provides the power of level 8. The general formula is that the faster and the longer I go past 25 km/h the longer time level 9 will not work. All other levels works just fine all the time.

It is very frustrating in a hilly city, where I can go with 40 km/h down hill and when I have to go up hill it will be with 20-22 km/h where the bike with my help would go 27 km/h.

The motor isn't just overheating. After going like 30 km/h level 9 will completely stop working for a while but level 8 (and the others) will work just fine. So I will get motor power by going to a lower power level.

Does anybody know about such a behavior? It is quite frustrating in several ways.

 

[sjpt]

One possibility is that it comes from some form of battery protection. The motor may not be hot, but not clear what is going on inside the highly stressed battery.

 

[vfr400]

Can you show a picture of the LCD control panel?

 

[SimonMikkelsen]

Here are 2 pictures with the LCD control panel turned on and with all possible symbols turned on (while starting). Thanks.

 

[Andy-Mat]

Here are 2 pictures with the LCD control panel turned on and with all possible symbols turned on (while starting). Thanks.

As someone has already alluded to, you may have a small battery, and it cannot supply the needed current well. A test with a higher capacity battery would tell you either way.
Thats what it sounds like to me personally....
Andy

 

[vfr400]

If it were the battery, it would cut off at low speed, where maximum current is drawn, not at 22km/h where current is reduced by the back emf.

 

[vfr400]

That's a standard Bigstone C6, C600, C7 or C700 display, the same as what comes with Das Kit. It's programmable, but you might need the password. It looks like they all start with 8, which leaves 999 possibilities. I know that some come without passwords, so you might be lucky.

There's a manual somewhere that you can download. I provided a link in a thread a month ago, but I can't find it now, nor the original download address. The manual covers all settings.

This Youtube video might help.

From memory, once you get past the password, there are two speed limit screens. One is for the throttle (t top right of LCD)and the other is for the PAS (p? top right). You have to set both.

Here is a manual, but it doesn't include the hidden settings. Maybe if you change to 6 levels of assist instead of 9, it might solve your problem. 9 is too many anyway.

Bigstone C600E-LCD Manuals

Bigstone C600E-LCD Pdf User Manuals. View online or download Bigstone C600E-LCD User Manual

www.manualslib.com

 

[SimonMikkelsen]

I didn't find the extended manual either (searched the forum on manual and Bigstone on your user) but I tried the max speed setting of the manual you posted, and upping it from 26 km/h to just 27 helped a bit and 28 even more.

But I did a test: I turned off the bike (i.e. the display) and drove down hill with at least 35 km/h, turned it on while still speeding. Then it did the same. When I drive with PAS 0 I can hear the motor a bit, but when I turn it off is says nothing. I guess that the motor or battery should not be active when the LCD is turned off.

Btw. when I set max speed to 40 km/h the bike gradually turned down power already at the usual 26 km/h so I guess this bike is definately has its limits.

 

[vfr400]

Did you set both the t and the p speed limits?
Did you try it with 6 PAs levels instead of 9?

The controller is switched off when the LCD is switched off, so there's no way that electricity can turn the motor. If you can hear the motor turning when switched off, it's being turned by mechanical means, so your clutch is probably stuck. Test it by rotating the wheel forward and reverse. You should feel a significant difference. If it's the same in both directions, your clutch is stuck. I'm assuming that you have a geared hub-motor, not a DD one. If you don't know what that means, show us what you have.

 

[Andy-Mat]

If it were the battery, it would cut off at low speed, where maximum current is drawn, not at 22km/h where current is reduced by the back emf.

That is totally wrong!
Someone who remembers only half the course content maybe?
If it were true, the faster you went the less power would be taken from the battery, which is obviously totally false...
As everyone here knows, the faster you go, the quicker the charge is used up!
You may be mistaking the indication from certain SOC meters, which go down as more current is drawn....BIG ERROR!
I have tried to educate you previously about such things. Without any success...
Its a very poor indication of your basic level of electrical knowledge, which you have made before here, and then you have simply gone ballistic to "cover up" your errors, and after being called out, and very rude as well......
I have also mentioned before that for a "self called" expert on e-bikes, your lack of electrical knowledge is really obvious to many here.....
I bet you go ballistic again!
Wait up people.....

 

[SimonMikkelsen]

Did you set both the t and the p speed limits?
Did you try it with 6 PAs levels instead of 9?

I think I need to find the extended manual. There was only a single max speed (SET2 in the manual) and no options for PA levels (which like you say would be nice with only 6 instead of 9). I tried holding + and - down for a long time but got no pincode screen (or anything else), like in the video.

The controller is switched off when the LCD is switched off, so there's no way that electricity can turn the motor. If you can hear the motor turning when switched off, it's being turned by mechanical means, so your clutch is probably stuck. Test it by rotating the wheel forward and reverse. You should feel a significant difference. If it's the same in both directions, your clutch is stuck. I'm assuming that you have a geared hub-motor, not a DD one. If you don't know what that means, show us what you have.

When switched of or set to PA 0 I hear the motor is switched off. When PA is 1 or higher I can hear the motor working a bit even when going so fast it should not help. So I think the motor part is ok. Because I experience the problem even when going fast with everything switched off, I have thought about a sensor or some part of the system that end up holding a charge for longer than intended. E.g. like a capasitor that when charged above a certain level, would cause the motor to switch off - but only on PA level 9.

That is totally wrong!
...
I bet you go ballistic again!
Wait up people.....

Obviously I don't know if you two have a history, but personal battles are no good in public.

To clarify, my bike draws maximum power both a low speeds and up to about 25 km/h. From a general electric point of view the battery should be pushed as much at 10 km/h as at 35 km/h (where it should not help at all) but I don't know the finer implementation details of e bikes, so I'll have to ask the experts about what is really happening when I go fast and the motor should not help me.

 

[danielrlee]

That is totally wrong!
Someone who remembers only half the course content maybe?
If it were true, the faster you went the less power would be taken from the battery, which is obviously totally false...
As everyone here knows, the faster you go, the quicker the charge is used up!
You may be mistaking the indication from certain SOC meters, which go down as more current is drawn....BIG ERROR!
I have tried to educate you previously about such things. Without any success...
Its a very poor indication of your basic level of electrical knowledge, which you have made before here, and then you have simply gone ballistic to "cover up" your errors, and after being called out, and very rude as well......
I have also mentioned before that for a "self called" expert on e-bikes, your lack of electrical knowledge is really obvious to many here.....
I bet you go ballistic again!
Wait up people.....

Andy, you're talking about two very different things. You're referring to the power required to maintain a given speed. VFR is referring to the current draw of a motor through its entire RPM range and the effect of the BEMF on this current draw.

IMO, VFR is correct. Current draw is higher at lower speeds for a given system due to the effect of the opposing BEMF at higher speeds.

 

[Deleted member 25121]

To clarify, my bike draws maximum power both a low speeds and up to about 25 km/h. From a general electric point of view the battery should be pushed as much at 10 km/h as at 35 km/h (where it should not help at all) but I don't know the finer implementation details of e bikes, so I'll have to ask the experts about what is really happening when I go fast and the motor should not help me.

vfr200 is correct, the back EMF created inside electric motors limits their maximum RPM at which point the power and current drawn reduces:

 

[vfr400]

I think I need to find the extended manual. There was only a single max speed (SET2 in the manual) and no options for PA levels (which like you say would be nice with only 6 instead of 9). I tried holding + and - down for a long time but got no pincode screen (or anything else), like in the video.

There are different software versions. you don't always get access to all the settings.

When switched of or set to PA 0 I hear the motor is switched off. When PA is 1 or higher I can hear the motor working a bit even when going so fast it should not help. So I think the motor part is ok.

That's normal and how it should work. the motor will spin as long as you pedal and the PAS level is 1 or more.

Because I experience the problem even when going fast with everything switched off, I have thought about a sensor or some part of the system that end up holding a charge for longer than intended. E.g. like a capasitor that when charged above a certain level, would cause the motor to switch off - but only on PA level 9.

In 10 years of working with these things, I've never heard of that problem. I don't believe that there's anything other than software that could cause it.

Obviously I don't know if you two have a history, but personal battles are no good in public.

Don't take any notice of him. He's just a troll. He knows nothing about how electric bikes work.

To clarify, my bike draws maximum power both a low speeds and up to about 25 km/h. From a general electric point of view the battery should be pushed as much at 10 km/h as at 35 km/h (where it should not help at all) but I don't know the finer implementation details of e bikes, so I'll have to ask the experts about what is really happening when I go fast and the motor should not help me.

You only know how much power your motor draws if your LCD displays watts or you use a wattmeter. The controller holds the maximum current from zero speed up to the speed that the back emf in the motor prevents it from reaching that maximum current. As the speed increases above that, the current ramps down to zero at the theoretical maximum speed when (motor rpm)x(motor KV) = (battery voltage). The speed at which that happens depends on the motor KV and the controller's maximum current.

 

[Andy-Mat]

I think I need to find the extended manual. There was only a single max speed (SET2 in the manual) and no options for PA levels (which like you say would be nice with only 6 instead of 9). I tried holding + and - down for a long time but got no pincode screen (or anything else), like in the video.



When switched of or set to PA 0 I hear the motor is switched off. When PA is 1 or higher I can hear the motor working a bit even when going so fast it should not help. So I think the motor part is ok. Because I experience the problem even when going fast with everything switched off, I have thought about a sensor or some part of the system that end up holding a charge for longer than intended. E.g. like a capasitor that when charged above a certain level, would cause the motor to switch off - but only on PA level 9.



Obviously I don't know if you two have a history, but personal battles are no good in public.

To clarify, my bike draws maximum power both a low speeds and up to about 25 km/h. From a general electric point of view the battery should be pushed as much at 10 km/h as at 35 km/h (where it should not help at all) but I don't know the finer implementation details of e bikes, so I'll have to ask the experts about what is really happening when I go fast and the motor should not help me.

Any vehicle, no matter what its power system, including a normal pushbike, requires more energy to go faster, than to go slowly.
The general rule from physics is to travel twice as fast, requires 4 times more energy.
Its a fact of both physics and life.
Is there anyone here who thinks/knows differently? Then please be so kind as to have a look at this website:-

Kinetic energy - Wikipedia

en.wikipedia.org

Where those interested will find the following, which is very easy to understand and can be liken to personal knowledge when driving most any vehicle:-
Since the kinetic energy increases with the square of the speed, an object doubling its speed has four times as much kinetic energy. For example, a car traveling twice as fast as another requires four times as much distance to stop, assuming a constant braking force. As a consequence of this quadrupling, it takes four times the work to double the speed.
In this case, "WORK" with regard to an e-bike, using no pedal power, is directly proportional to the amount of power being taken from the battery and being used to turn the electric motor. e.g. The faster you go, the more power is being used.
regards to all
Andy

 

[vfr400]

Any vehicle, no matter what its power system, including a normal pushbike, requires more energy to go faster, than to go slowly.
The general rule from physics is to travel twice as fast, requires 4 times more energy.
Its a fact of both physics and life.
Is there anyone here who thinks/knows differently? Then please be so kind as to have a look at this website:-

Kinetic energy - Wikipedia

en.wikipedia.org

Where those interested will find the following, which is very easy to understand and can be liken to personal knowledge when driving most any vehicle:-
Since the kinetic energy increases with the square of the speed, an object doubling its speed has four times as much kinetic energy. For example, a car traveling twice as fast as another requires four times as much distance to stop, assuming a constant braking force. As a consequence of this quadrupling, it takes four times the work to double the speed.
In this case, "WORK" with regard to an e-bike, using no pedal power, is directly proportional to the amount of power being taken from the battery and being used to turn the electric motor. e.g. The faster you go, the more power is being used.
regards to all
Andy

You're getting current, power and energy mixed up. As a motor speeds up, current goes down because the back emf is proportional to its speed. At zero rpm, the whole battery voltage is available to the motor to push current through it. At 50% of its max speed, only half the battery voltage is available and at max rpm, there is zero voltage, which is why it no longer can provide power and won't go any faster.

Instead of spouting stuff from wiki, use the simulator to see how it all works.

Motor Simulator - Tools

Our ebike motor simulator allows you to easily simulate the different performance characteristics of different ebike setups - with a wide selection of hub motors modeled, and the ability to add custom batteries and controllers and set a wide variety of vehicle parameters you'll be able to see...

www.ebikes.ca

 

[SimonMikkelsen]

Any vehicle, no matter what its power system, including a normal pushbike, requires more energy to go faster, than to go slowly.

When a bike is going 25 km/h it has a kinetic energy, i.e. potential energy. You only use energy to get to this point (accelerate), but unless another force is acting upon the bike it takes no additional energy isneeded to stay at your current velocity. That is why space crafts can travel for many years on a single burn, because there is no resistance from air.

In the real world you have friction in the bike, from the road, from the air and from gravity (when going up hill) which subtracts energy from your system (you + bike). That has nothing to do with the potential energy and is much more complicated to calculate than just squaring the speed.
Kinetic/potential energy has nothing to do with the energy needed to maintain a given speed. You mostly have to think about your kinetic energy when braking, because then you want to remove it.

 

[vfr400]

When a bike is going 25 km/h it has a kinetic energy, i.e. potential energy. You only use energy to get to this point (accelerate), but unless another force is acting upon the bike it takes no additional energy isneeded to stay at your current velocity. That is why space crafts can travel for many years on a single burn, because there is no resistance from air.

In the real world you have friction in the bike, from the road, from the air and from gravity (when going up hill) which subtracts energy from your system (you + bike). That has nothing to do with the potential energy and is much more complicated to calculate than just squaring the speed.
Kinetic/potential energy has nothing to do with the energy needed to maintain a given speed. You mostly have to think about your kinetic energy when braking, because then you want to remove it.

I can add a bit to that. It takes approximately 250w to drive an MTB type bike at 25 km/h on a flat road. At that speed, complete system efficiency will be around 70%, so we can say 357 watts from the battery. With a half-empty battery, voltage would be around 36V, so current would be 9.9 amps. That's without pedalling. If you add 100w of pedal power, the current comes down to 7.1 amps.