Ninebot One Z : Z6-Z8-Z10

[houseofjob]

11 minutes ago, Scatcat said:

Gaaaaaah!

I'm already looking at my bank balance and starting to rationalise how it really wouldn't hurt so much to make a z-shaped hole in my savings... 

[kasenutty]

Buy Bitcoin 

[EricGhost]

It's good to know that NB/Segway it's still in the EUC market, this in the long term will only benefit the products. Big companies are slower but when they move they always do a big step forward even if not always successfully.

Maybe you can remember Merceds 1rst class A car model big advertisement, high expectations and .... hoops unstable car, but in the end ..... 

so competition will rise I hope and products design & manufacturing must follow ..... I hope so ...

Edited August 15, 2017 by EricGhost

[noze02]

8 hours ago, MaxLinux said:

What are the advantages/disadvantages of using a tubeless tire on a EUC?

You can ride with a lower pressure (more contact area=more traction) without the risk of puncturing the tube.

I think nobody mention it, but a fat tire apart from giving more traction it can make the ride more confortable (the air inside the tire works as a suspension as the air is compresible).

Quite excited with the new One Z, lets see in October when they released over here, maybe I need to get one :-)

[ir_fuel]

6 hours ago, kasenutty said:

Buy Bitcoin 

I just did that last week.

It went from 2900 to 3700 euro for 1 BTC 

But I only bought for 400 euro 

5 minutes ago, noze02 said:

I think nobody mention it, but a fat tire apart from giving more traction it can make the ride more confortable (the air inside the tire works as a suspension as the air is compresible).

Good point. You get a bigger shock absorber. Interesting for off road.

[Mono]

1 hour ago, noze02 said:

You can ride with a lower pressure (more contact area=more traction) without the risk of puncturing the tube.

Agreed, it's nice to be able ride with lower pressure without risking snakebites. The main advantage is IMHO better comfort. More contact area does not change the traction in principle, because the pressure on this area is lower and both effects cancel out. Exceptions granted, but probably both ways. 

Quote

I think nobody mention it, but a fat tire apart from giving more traction it can make the ride more confortable (the air inside the tire works as a suspension as the air is compresible).

That's the original main point of the fat tire concept, AFAICS. It provides enough suspension to make "real" suspension superfluous. Comfort pure.

The main reason for air in the tire is shock absorption in the first place. The awesome absorbing properties of air are the reason why airless competitors are never really catching on.

Edited August 15, 2017 by Mono

[Mono]

12 hours ago, MaxLinux said:

What are the advantages/disadvantages of using a tubeless tire on a EUC?

Tubeless becomes also more and more popular for bicycles as well. EUCs are even better suited for the technology, because they usually don't have holes in the rim.

Apart from the already above mentioned: 

• Apparently more difficult to pump up. I guess it is because they leak air left and right until there is already some reasonable pressure in the tire.
• Apparently more difficult to mount (I have zero experience). 
• Can be used with a tube as well, which can come in handy in case of a defect abroad.
• Generally more resistant to defects. On bicycles, putting a liquid sealant seems to be obligatory for the installation. Without, the tire may be leaking air immediately. The sealant has to be renewed from time to time.

[Scatcat]

12 hours ago, houseofjob said:

I SHOULD have seen that one coming 

[LanghamP]

On 8/14/2017 at 10:31 AM, ir_fuel said:

That makes no sense. Skinny tires give less friction so they allow you to go faster with the same force because of the smaller contact patch . Weight isn't an issue. The traction issue is also non existent as you can't spin a bicycle tire or a euc tire, there isn't enough torque to break traction. That's for cars and motorbikes.

 

Mtb tires are wide and stubbier so they can find traction over a bigger surface since it usually is uneven. Making a wide slick wouldn't help.

 

 

[andress]

23 hours ago, Marty Backe said:

The cheapest/junkiest batteries in the world would have nothing to do with overheating wires. Batteries push out electrons. If anything, cheap batteries can't pump out the electrons fast enough which would result in cooler wires. Cheap batteries can cause battery pack problems, but not wiring harness or control board failures.

Until I see specifics, like "I opened up the battery pack and found XYZ batteries, and here are the pictures to prove it", I consider this unsubstantiated gossip. But if you ever find actual evidence, I and others would be very interested in reading about it.

Actually the voltage sag that is more pronounced with bad batteries would cause higher currents running through the wires while using the same wattage and since it is current and not voltage heating the wires up it could actually in theory worsen the situation with overheating wires.

[US69]

21 minutes ago, andress said:

Actually the voltage sag that is more pronounced with bad batteries would cause higher currents running through the wires while using the same wattage and since it is current and not voltage heating the wires up it could actually in theory worsen the situation with overheating wires.

Thats not the case...

The gotway problems with overheated wires was not on wires from batterie to board...it was from board to motor, where the motor needed an amount of amps that was asked from the board. whatever batteries you have does not play a role here, it was just not batterie related.x

Other than that @Soju i would like to question that "cell" rumour, and would like to know more, as Gotway can be blamed for a lot of things, but not for there batteries.

Gotway uses the the same batterie type since the V3\Acm...Sanyo or Panasonic!

In our specifications, there are not much other which can be used!

 

about 2 years ago there was one case, where they put a wrong batterie type in a few wheels, and had that "cell sheater"running after them for a longer time! Perhaps this "rumour" has stayed over from that time...

 

[Mono]

If the battery provides a lower voltage, isn't this also the voltage the motor "sees"? (And hence we need larger motor currents to deliver the same power a longer duty cycle to maintain the motor current but it doesn't need to increase). Otherwise I wouldn't understand why in these graphs

http://forum.electricunicycle.org/topic/7549-current-demand-versus-battery-voltage/?page=3#comment-106384

maximal motor current depends on battery voltage. Of course the maximal current drops with a voltage drop. But if the constraint is constant power output the current should go up. 

Edited August 16, 2017 by Mono

[Chriull]

7 hours ago, andress said:

Actually the voltage sag that is more pronounced with bad batteries would cause higher currents running through the wires while using the same wattage and since it is current and not voltage heating the wires up it could actually in theory worsen the situation with overheating wires.

For the same wattage (output power) at the same speed the torque and hence the motor current is the same. Battery voltage has no influence on the motor current, as long as it is high enough - once it is below the needed motor voltage, the motor current decreases and by this the output power ( max torque over speed limit is reached).

the motor voltage is always lower than the battery voltage - this is provided by the controller which "steps down" the battery voltage as needed.

by lower battery  voltage just the average battery current rises accordingly - but the battery current is always lower than the motor current and at the battery side there is no thermal problem with the wiring, etc. (but also this was already misdesigned/badly manufactured by some wheel producers, having the cell conections heat up to melt the battery pack wraps...)

for details see http://forum.electricunicycle.org/topic/7549-current-demand-versus-battery-voltage/

 

6 hours ago, Mono said:

If the battery provides a lower voltage, isn't this also the voltage the motor "sees"? (And hence we need larger motor currents to deliver the same power).

As before - output power is torque times speed, current is direct proportional to torque, so constant power output at constant speed gives a constant current.

to overcome a constant force ( uniform acceleration, incline,... disregarding air drag) needs a constant torque and by this constant current.

Quote

Otherwise I wouldn't understand why in these graphs

http://forum.electricunicycle.org/topic/7549-current-demand-versus-battery-voltage/?page=3#comment-106384

maximal motor current depends on battery voltage. Of course the maximal current drops with a voltage drop. But if the constraint is constant power output the current should go up. 

The maximal motor current flowing at zero speed is battery voltage divided by the resistances, which are the internal resistance of the battery and the ohmic coil resistance (+ wiring, contacts and mosfets).(1) The other point of this limit line is when the generated back emf of the motor equals the battery voltage. So this limit line moves to/from the origin dependend on the battery voltage.

so also by lower battery voltage the maximal possible power output drops - its then easier to overlean the wheel.

Edit: by battery voltage drop the max current line shifts "left and down" and by this the max power output possible decreases. With a constant power output as constraint the motor current stays constant (at the same speed) as long as this constant power (speed/torque= current point) is within the possible limits. Once it is outside the possible li its the constraint can't be kept up anymore and power and current decreases.

(1) ignoring of course the current limiting of the controller - thats just a theoretical point to construct the line.. 

Edited August 16, 2017 by Chriull

[ir_fuel]

All this discussion about batteries ....

 

Can't they just make one that runs on petrol? 

[Tomek]

1 hour ago, Chriull said:

 

the motor voltage is always lower than the battery voltage - this is provided by the controller which "steps down" the battery voltage as needed.

I don't think that's correct, i.e. the controllers limit the current, not voltage (unless I mixed something up) that goes to the motor. The torque, speed, power relationship may be misleading in this context. From electrical perspective Power (W)  = current (A) x voltage (V) (Ohm's law), so the higher the voltage of the battery, the more power goes to the motor, providing that the controller pushes the same amount of current in both cases.

[Tom Fagerland]

38 minutes ago, ir_fuel said:

All this discussion about batteries ....

 

Can't they just make one that runs on petrol? 

Or pedals. Honestly, a self-balancing pedalled unicycle would be pretty cool...

[WaveCut]

1 minute ago, Tom Fagerland said:

a self-balancing pedalled unicycle

Already invented by nature. Called - legs!

[Tom Fagerland]

4 minutes ago, WaveCut said:

Already invented by nature. Called - legs!

Nah, needs improvement...

[Chriull]

9 minutes ago, Tomek said:

I don't think that's correct, i.e. the controllers limit the current, not voltage (unless I mixed something up) that goes to the motor. The torque, speed, power relationship may be misleading in this context. From electrical perspective Power (W)  = current (A) x voltage (V) (Ohm's law), so the higher the voltage of the battery, the more power goes to the motor, providing that the controller pushes the same amount of current in both cases.

I know that it is correct  if you want to know more about this you could read the links in the i provided before

Edited August 16, 2017 by Chriull

[Mono]

47 minutes ago, Chriull said:

I know that it is correct  if you want to know more about this you could read the links in the i provided before

Is this mainly a matter of technology choice? I mean, is it in general/principle possible to modulate current instead of voltage to control motor current? Or is it even more or less a matter of viewpoint of the duty cycle? 

Edited August 16, 2017 by Mono

[Chriull]

17 minutes ago, Mono said:

Is this mainly a matter of technology choice?

It's no choice - all EUCs (and BLDC controller as far as i know) function similar.

For a asked force (acceleration, incline, air drag, bump, balancing, etc...) at a certain speed a certain torque is needed. For this torque a certain current is needed. The motor generates a speed depending Back EMF and has a voltage drop along the coils.

So with the known Back EMF (measured by the controller, resulting from the rotational speed) (1) the current battery voltage is "stepped down" so that exactly the current for the actual needed torque is flowing. ( For a static system more or less I motor = (U_stepped_down-Umotor)/Rcoil. With Umotor = U back emf + Imotor * Rcoil)

Imho this is acomplished by the PID algorithm for stabilizing the wheel.

Quote

I mean, is it in general/principle possible to modulate current instead of voltage to control motor current?

Current and voltage are not freely "adaptable/to be choosen" - the motor has for each "working point"(speed/torque) a certain current/voltage "need". If this is not "satisfied" the "working point" changes. So if one modulates the current a certain voltage will "arise" - if one modulated the voltage a certain current will flow. So it's more a viewpoint matter than a real choice what (current or voltage) is modulated. 

Edit: (1) maybe also not measured? could be that the back emf (their zero crossing) is just used instead of/additionally to hall sensors. Since the motor current of two of the motor phases are measured and the sum of all three is always zero this currents are the "control variable" for the balancing algorithm. But for implementation details "our" members from the firmware thread are the competent contact persons...

Edited August 16, 2017 by Chriull

[Mono]

I am still trying to understand what you mean precisely by "modulate".

Is it not correct to say that the controller "passes" to the motor, depending on the duty cycle, either 0V or the battery voltage (which then undergoes the forced "step down")? In other words, there are only two voltages interlaced (from which we could compute a weighted average voltage)? Or in other words, the controller just turns the motor on and off repeatedly in very short periods of time?

Edited August 16, 2017 by Mono

[Tomek]

well, it's probably just a matter of wording things. if you only look at the current and voltage that goes into the controller, the current is dynamic and voltage is constant. The controller does a lot of "magic" with feeding electricity to the coils, such that the motor spins at a required speed and with required torque, and it does it does it super-fast. However, to the best of my knowledge, the controller can't "step down the voltage". It technically only opens and closes the transistors, but at very high speeds, which effectively can control the speed and torque of the motor. btw. PWM outputs of microcontrollers follow a similar principle. They don't "step down" the voltage, but by turning the output on and off at full voltage, you can create the effect as if the voltage was decreasing (e.g. a LED on your Arduino will fade down).

considering the toque equation, you can also say that if torque = power / speed then toque (in an instance of time) = current (flowing in that moment to the motor controller) x voltage (feeding the motor controller) / speed (of the motor). how current and voltage are specifically divided and fluctuating across the three motor phases, i.e. what happens between the controller and the motor is of no importance from this perspective IMO. Of course, due to heat losses, the power consumption of the motor will be a bit lower than the power consumption of motor+controller. 

[US69]

28 minutes ago, Tomek said:

well, it's probably just a matter of wording things. if you only look at the current and voltage that goes into the controller, the current is dynamic and voltage is constant. The controller does a lot of "magic" with feeding electricity to the coils, such that the motor spins at a required speed and with required torque, and it does it does it super-fast. However, to the best of my knowledge, the controller can't "step down the voltage". It technically only opens and closes the transistors, but at very high speeds, which effectively can control the speed and torque of the motor. btw. PWM outputs of microcontrollers follow a similar principle. They don't "step down" the voltage, but by turning the output on and off at full voltage, you can create the effect as if the voltage was decreasing (e.g. a LED on your Arduino will fade down).

 

1 hour ago, Mono said:

Is it not correct to say that the controller "passes" to the motor, depending on the duty cycle, either 0V or the battery voltage

As far as i know the Controller not only passes the Batterie voltage to the Motor...With the big capacitors it is even holding a certain amount of (higher)Voltage, so that it never goes down under a specific value. Without capacitors the wheel is working but as soon some power is needed you are going to faceplant....i had experienced that myself on a capacitor-defect KS16.

That's why i think what happens with voltage/amps delivered by Batterie before the board is totally different to what arrives at the Motor After the board!

@zlymex had some nice measurement which Show that very nicely, or?

[Mono]

9 minutes ago, KingSong69 said:

With the big capacitors it is even holding a certain amount of (higher)Voltage

They are not only used to account for voltage drops of the battery but also used to increase the voltage above the max battery voltage?

What's roughly the size of these capacitors?