My Z10 Triumphs, Tribulations, and Failures

[Toshio Uemura]

37 minutes ago, mrelwood said:

If I fully charged the 16S to 100%, it didn’t take more than a slightly stronger braking on a flat surface to make the overcharge alarm go off. If you live on top of a hill, you should never start by going downhill with a 100% battery.

The 100% charge is a hard limit, so any regen at that point will make the alarm go off, and hard tilt-back should follow very soon.

The hill people will have to have a method of discharging a bit after a balancing charge that takes all cells to 100%.

Is there a good way for the hill people to discharge the wheel let’s say to 90% after a balancing charge or an overnight charge? Anything other than playing music over the internal speakers or riding in ⭕️ circles until you get dizzy? Anyone has any practical ideas? ?

[EUCMania]

Z10 charging only one pack during braking is a design flaw because, as @Toshio Uemura pointed out that it will lead to overcharging one of the battery pack during long downhill ride.

[Toshio Uemura]

6 minutes ago, Mark Lee said:

I don't really have any problem riding this wheel like the others.  Reminds me of big Mten3... 

Try downhills, steeeeep downhills. ? 

[EUCMania]

4 minutes ago, Toshio Uemura said:

Is there a good way for the hill people to discharge the wheel let’s say to 90% after a balancing charge or an overnight charge? Anything other than playing music over the internal speakers or riding in ⭕️ circles until you get dizzy? Anyone has any practical ideas? ?

Use a timer, or Charge Doctor, but it will not balance battery cells though

[Toshio Uemura]

2 minutes ago, EUCMania said:

Z10 charging only one pack during braking is a design flaw because, as @Toshio Uemura pointed out that it will lead to overcharging one of the battery pack during long downhill ride.

I wouldn’t raise the “design flaw” card so fast. There still is some mystery left to be explained. I wish one of the Ninebot people or engineers would comment on that if they can. ?

[Toshio Uemura]

5 minutes ago, EUCMania said:

Use a timer, or Charge Doctor, but it will not balance battery cells though

That’s a start. And once in a while for a balancing charge they have to stay overnight at granny’s house ? downhill or rent a second flat in the valleys. Might come in handy for other purposes too. ? 

[Mark Lee]

33 minutes ago, Toshio Uemura said:

Try downhills, steeeeep downhills. ? 

Yup did have major wobble during our group ride couple of weeks ago on steep decent.  I will update with more rides to come...

[Marty Backe]

1 hour ago, Mark Lee said:

@Toshio Uemura with all of your positive posts on Z10, I got mine today... Got a deal I could not pass up... 

You bought the one from San Francisco (I think) - he preferred smaller wheels

?

[Mark Lee]

Just now, Marty Backe said:

You bought the one from San Francisco (I think) - he preferred smaller wheels

?

No got the one I've been riding on our group rides.  Gustesta has a bad back and Z10 was just too heavy for him...

[stephen]

so! let's say you live on a big hill maybe half a mile long at 20%grade at 80-90kg what charge would it actually put back in .. are we talking allot or abit lol? 

[who_the]

On 8/28/2018 at 8:35 PM, Hunka Hunka Burning Love said:

@who_the, has no one in San Francisco gone down a steep hill and lost control of their wheel for whatever reason?  That’s kind of like saying I’ve ridden 2000 km and never fallen.    You know it’s bound to happen the next day, and the consequences sometimes aren’t that pleasant.

I think maybe a looped tether line with a quick clip isn’t the end of the world if used wisely.   I don’t ride down extremely steep hills, but I rue the day some bystander gets hurt by a 50 lb wheel flying down at them out of control.  Mark my words.    

https://www.nbcbayarea.com/news/local/Three-Injured-After-Truck-Careens-Down-SF-Street-454344883.html

No, it hasn't happened here to my knowledge. I do have a heavy-duty coiled tether I haven't used since my KS14C. Other than the inconvenience, or a potential entanglement, using a tether certainly couldn't hurt. But in many thousands of miles of safe EUC riding here in the Bay Area, among dozens of riders, up and down literally the steepest hills in our city, I'm not aware of a single "runaway" wheel down a hill.

[who_the]

Although it has certainly happened elsewhere...

Ride responsibly everybody.

 

 

[Marty Backe]

2 hours ago, Mark Lee said:

No got the one I've been riding on our group rides.  Gustesta has a bad back and Z10 was just too heavy for him...

That was him - too many names & places  I saw the ad and that it was bought within a couple of hours 

Congrat's.

[Toshio Uemura]

2 hours ago, who_the said:

Although it has certainly happened elsewhere...

Ride responsibly everybody.

 

 

How many wheels will it take him to master this slope? Three? May be four? Or even five! An expensive learning experience. Wish one could practice decents like this in a simulator first. 

[mrelwood]

25 minutes ago, Toshio Uemura said:

How many wheels will it take him to master this slope? Three? May be four? Or even five! An expensive learning experience. Wish one could practice decents like this in a simulator first. 

One really should to start with short ones, and incrementally add steepness and length. And stand back on the pedals! The issue on the video was not that the wheel couldn't brake (wheel stayed upright), but the rider didn't get enough momentum at the back of the pedals.

[Mono]

1 hour ago, Toshio Uemura said:

How many wheels will it take him to master this slope? Three? May be four? Or even five! An expensive learning experience. Wish one could practice decents like this in a simulator first. 

If he would have been smart, he would have started below the middle of the lowest ramp in his first try. Then the answer would be zero, but the vid wouldn't have made it to the social media.

[Mark Lee]

7 hours ago, Marty Backe said:

That was him - too many names & places  I saw the ad and that it was bought within a couple of hours 

Congrat's.

It would of been sad event for our group to not have Z10 in our inventory.  Everyone in our group loves to ride it... 

[Mike Paolini]

11 hours ago, Toshio Uemura said:

Is there a good way for the hill people to discharge the wheel let’s say to 90% after a balancing charge or an overnight charge? Anything other than playing music over the internal speakers or riding in ⭕️ circles until you get dizzy? Anyone has any practical ideas? ?

I live halfway up on a hill, after full charge, I always start by riding up to the top, and then coming down.

I think another option may be a very slow side to side S down the hill.  I'll have to try that one though.

 

[Daniel Burkemper]

10 hours ago, Toshio Uemura said:

How many wheels will it take him to master this slope? Three? May be four? Or even five! An expensive learning experience. Wish one could practice decents like this in a simulator first. 

At the very least, a tether would help mitigate the wheel damage. Also a brain would help stop the wreckage altogether. 

[meepmeepmayer]

On 9/2/2018 at 5:28 PM, Arbolest said:

(loooong post)

I'm no expert by any means, but I have some comments (or rather conjectures how I see it), if only because you put so much effort in Also this touches the good old "When do we have regeneration and when not when going downhill?" question, and that  is as unanswered as ever So:

• I don't think the back-EMF does add much to the braking. Just push your wheel fast while it's off, and you see it isn't really that much resistance, not enough for seriously braking a human rider. So any wheel will have to do the usual active motor braking to slow down (what you refer to as pushing). But of course the motor slowing you down automatically helps.
• I wouldn't necessarily mix together back-EMF and regeneration.
  Back-EMF means the faster you go, the less efficient (?) the motor becomes because there's the rising counterforce. You still use energy at any speed, don't get anything back. You just have a backward force/acceleration rising with speed. So it matters more for going at a certain constant speed.
  Regeneration, meanwhile, happens when you decelerate and that kinetic energy has to go somewhere. Apparently it charges the battery, even though the motor actively does work to brake. F***k me if I know why or how that can be, but it happens, and it surely meshes together somehow with the motor turning, the same thing that causes back-EMF. The details are a big mystery to me Anyways, regeneration happens when you change your speed (reduce it), specifically when you decelerate.

On 9/2/2018 at 5:28 PM, Arbolest said:

First, think about this from the wheel's perspective if you can. Dealing with inclines and declines is quite a bit different than riding around on a nice flat road somewhere. When you're riding up or down on a slope, the wheel also has to deal with your weight, which is a big deal for these machines because they're essentially having to either work with or fight against a constant acceleration. That means that just staying still means putting out a lot of power if the slope is even slightly steep, much less actually accelerating on it!

That seems completely correct and is a good mental model. A slope adds a constant extra acceleration (from gravity) for the wheel to overcome.

In general, since force = mass times acceleration, and your and your wheel's weight don't change, forces and accelerations are interchangeable.

So we have the following effective forces/accelerations acting on a wheel (in the horizontal/forwards-backwards direction, the others don't matter here):

• The big one, air resistance. Rises disproportionately with speed. Always works against the riding direction unless you happen to have crazy tailwinds.
• Back-EMF, also rises with speed. It's always against the riding direction.
• As soon as you have some slope, you get the horizontal component of gravity (which vanishes on flat ground). Acts against the riding direction uphills and with the rider downhills.
• Tire rolling resistance (just for completeness' sake, it's there but doesn't do much else, it's just background noise), always against the riding direction.
• The quick dynamic back/forth pendulum accelerations the wheel has to do to keep the balance at any constant speed. Actually it's not much (energy wise) as mere balancing doesn't cost much and doesn't change much, so it's also just background noise.
• And now, the actual acceleration or deceleration required from the wheel when the rider leans to speed up or slow down.

And I would surmise when the net force/acceleration without the rider's input is forwards (= you get pushed downhill), you either get faster and faster and faster, or the rider adds a counterforce/deceleration to keep the speed or even slow down (a fancy way to say "the rider brakes"), and that's when regeneration happens (must happen?). Regeneration = the rider must add a deceleration to keep control.

On 9/2/2018 at 5:28 PM, Arbolest said:

In addition to this, and this is the kicker, the wheel has to deal with MOMENTUM. When going uphill, the wheel is applying power in the same direction as you are moving. It's working WITH your momentum. But downhill? Especially riding STEEPLY downhill? Whew, that must be torture for the poor little things... They have to work AGAINST your momentum. They have to:

1) Use power to keep you upright

2) Use power to hold up your weight (fighting an acceleration)

3) Use power to DIRECTLY OPPOSE YOUR DOWNHILL MOMENTUM

That last one, which anyone who has ridden one of their e-horses (I love that term, @Toshio Uemura) downhill at speed would know with startling clarity, is an incredible feat. The amount of kinetic energy these wheels are able to overcome can be truly astounding sometimes... Just imagine how much force that you (as a human being) would need to apply in order to try and slow down a fully grown adult going 15-20 miles per hour downhill within a reasonable distance...

This is mostly nitpicking, but since momentum is mass times speed, even downhills it doesn't change when you just go along. But to keep your momentum (and to not get faster and faster and increase the momentum) the wheel has to apply a force (which is just a change in momentum) to counteract the gravity acceleration trying to increase momentum.

Same idea, on flat ground, you have air and tire resistance and back-emf forces the wheel has to overcome to keep your momentum (=speed). That's why riding costs energy, mostly.

I think you're right that going down steep hills (and braking) is the hardest for a wheel to do. It is for the rider at least Not sure why, though. The actual power requirements are lower. But maybe because you're faster downhills, back-EMF and more kinetic energy make the difference?

On 9/2/2018 at 5:28 PM, Arbolest said:

In case that didn't make sense, try this mental image on for size: Consider that riding on an incline is like constantly riding your wheel while aggressively leaning forward/backward on a flat road. If you're riding up or down a hill with a 20 degree slope, that's effectively like trying to accelerate/brake by leaning forward or backward by 20 degrees on a flat road. Now imagine adding in the stress of breaking on top of that, and you'll start to see how much power you're actually asking from the wheel.

Hm... the general idea seems good. Just as leaning forwards requires an acceleration from the wheel, so does gravity add a forward acceleration downhills that's suddenly there that the wheel has to counter. So I guess you're more or less right there.

--

Now for your Z10 theory, I don't think that can work.

• Back-EMF is there whether you like it or not, so the Z10 "only" using active motor-braking doesn't make sense to me. How could it?
• Same for regeneration, can you even have no-regeneration despite decelerating the wheel?

So I'd say:

• The weak braking is either a firmware feature (for whatever reason) or they limited the braking to prevent too high stresses on the electronics. Not sure if/how exactly stresses are higher than going steep uphills where the Z doesn't feel weak like this.
• The fact that only one of the batteries is getting recharged is just an engineering quirk or design, along with the fact that the two battery packs can have different voltages in the first place. How do you even drive a motor with two batteries at different voltages?
  What explains the "less" regeneration the Z has according to Marty? Where does the energy go? Good question

I don't think there is something different with the Z10 in the principle of how it works. Back-EMF will always brake the motor. Regeneration is always going to happen (...right?). They just designed the wheel differently. Maybe this is where the low voltage shows somehow?

It's a mystery, and we really could need a proper physicist or electric engineer here to uncover the secret behind how these damn wheels actually work

Edited September 3, 2018 by meepmeepmayer

[palachzzz]

25 minutes ago, meepmeepmayer said:

I don't think the back-EMF does add much to the braking. Just push your wheel fast while it's off, and you see it isn't really that much resistance, not enough for seriously braking a human rider. So any wheel will have to do the usual active motor braking to slow down (what you refer to as pushing). But of course the motor slowing you down automatically helps.

Just connect all the motor wires together, and try again. 

[Toshio Uemura]

59 minutes ago, Daniel Burkemper said:

At the very least, a tether would help mitigate the wheel damage. Also a brain would help stop the wreckage altogether. 

You see this kind of decent a lot with snowboarders on their first days.

 

[Jekyll_500]

Are you sure that only one battery is being charged while braking? I‘m quite sure the S2 always tries to charge its batteries equally. Do I have to try braking only softly with a rider weight of ~200pounds? I have never had problems with the E+ or the S2 but they are also much slower...I‘m reading now a lot about power problems. I don’t like the style of the Kingsong Wheels, but would the KS18-L be a better performer for heavy riders? Price would be about the same (Z10 a bit cheaper)

[meepmeepmayer]

56 minutes ago, palachzzz said:

Just connect all the motor wires together, and try again. 

Yes but the wheel doesn't short itself while braking, does it? So the battery (or the capacitors? I wonder what will happen if you keep pushing a wheel with the battery disconnected) acts as a buffer.

Edited September 3, 2018 by meepmeepmayer

[Meelosh123]

Is it possible to avoid any overcharging simply by bombing the hill and refusing to decelerate?