My Z10 Triumphs, Tribulations, and Failures

[Toshio Uemura]

13 minutes ago, Meelosh123 said:

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

Yes! Very possible! BUT you would get arrested and only your children and grandchildren could enjoy the benefits of a flattened hill.

However learning how to decent on your EUC with its power OFF might be the solution. You can then switch it ON at the bottom of your hill. No bombing required. ? 

Edited September 3, 2018 by Toshio Uemura

[meepmeepmayer]

14 minutes ago, Meelosh123 said:

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

In theory that should work. But imagine you are in some other unbraked vehicle rolling down a hill, it gets too fast very soon. Same with a EUC. So you always have to brake sooner or later. Otherwise you might just ride off a cliff and have the same result

But overcharging is no problem, the wheel will warn you when the battery is full. Worst case, you have to ride up the mountain a bit to lose battery before going further down. Just never ignore the overcharge warnings or the wheel will have to switch off.

Or did you mean recharging? I believe that happens whenever you brake, but I'm not sure how exactly.

[Mono]

52 minutes ago, Meelosh123 said:

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

It would certainly be an interesting experiment that I wouldn't ever do myself out of health concerns. Please report back your final speed and how it went afterwards.

Edited September 3, 2018 by Mono

[Meelosh123]

I guess I’m not sure what distance/gradient will cause an overcharge shut off on a 100% battery. 20, 30, 100 feet of heavy decline really isn’t that insane.

I recently have been riding in some new territory (a golf club-town kinda neighborhood) that has some monster hills (dunno how long the steepest ones are, less than a quarter mile for sure), and the first time I did it it was pitch black out and I got some wobbles I could not recover from...just had to ride it out. Never had wobbles trying to slow down before. Setting my feet a bit further back helped with my center of gravity.

If i bombed that hill, and the motor really did not have to apply any power to keep the wheel going (because gravity was providing more than enough power), would the wheel cut out after a certain speed?

[Steef Klonoa]

Still anxiously awaiting the next move for my preorder on the Z10. Does anyone know if the beeping can be stopped when you get this wheel down to the last few miles? I was watching a video of Marty the other day and the beeping was really loud once he got near that 40 mile mark! I hope there is a way to disable that. Maybe through the app?

[justanut]

6 hours ago, Jekyll_500 said:

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)

Do not worry too much about “power” problems.. Those are simply gripes about what they “expected” vs what they are experiencing.. It's just different, in a good way. I feel very confident conquering inclines and as I have no need for sudden bursts of speeds (which I’m quite sure the Z10 can deliver, except I don’t usually lean in that much), I’ve been enjoying cruising on a wheel that gives me the confidence that I have full control. I was following behind a group of grans yesterday and had no problems keeping balanced, something I couldn’t accomplish on the V8. And I’m on 30 psi! Not one of those running on deflated wheels. This wheel just eats up all sorts of terrain. I have zero complaints.

[mrelwood]

1 hour ago, Steef Klonoa said:

Does anyone know if the beeping can be stopped when you get this wheel down to the last few miles?

All wheels beep and keep beeping when the battery charge level gets too low. It is there for protecting both the batteries and the rider. Don’t ride with low batteries is the only solution.

 

[mrelwood]

2 hours ago, Meelosh123 said:

I guess I’m not sure what distance/gradient will cause an overcharge shut off on a 100% battery.

Again, it doesn’t need more than a decent braking on level ground to make the alarm go off, so I don’t think there is very much play in the system.

2 hours ago, Meelosh123 said:

If i bombed that hill, and the motor really did not have to apply any power to keep the wheel going (because gravity was providing more than enough power), would the wheel cut out after a certain speed?

If you let the gravity accelerate the wheel, you’d be golden. But if you reach the top speed and the tilt-back forces you to stop accelerating, the regenerating power at that speed is large and will cause issues very fast.

Or if there is a sudden reason to brake after all, like a buch of kids running in front of you from behind a corner...

[Toshio Uemura]

3 hours ago, Meelosh123 said:

I guess I’m not sure what distance/gradient will cause an overcharge shut off on a 100% battery. 20, 30, 100 feet of heavy decline really isn’t that insane.

I recently have been riding in some new territory (a golf club-town kinda neighborhood) that has some monster hills (dunno how long the steepest ones are, less than a quarter mile for sure), and the first time I did it it was pitch black out and I got some wobbles I could not recover from...just had to ride it out. Never had wobbles trying to slow down before. Setting my feet a bit further back helped with my center of gravity.

If i bombed that hill, and the motor really did not have to apply any power to keep the wheel going (because gravity was providing more than enough power), would the wheel cut out after a certain speed?

What kind of hills are we talking here? This kind? I need to ride that down once in a while, when I stay at my relatives over night in Kobe. It goes on for about a mile or so.

 

[kasenutty]

That hill has wheels, like a big cement semi trailer.

[Toshio Uemura]

16 minutes ago, kasenutty said:

That hill has wheels, like a big cement semi trailer.

Earthquake protection feature! ? 

[mrelwood]

1 hour ago, Toshio Uemura said:

What kind of hills are we talking here? This kind? I need to ride that down once in a while, when I stay at my relatives over night in Kobe. It goes on for about a mile or so.

 

In my understanding you would be on your butt in a few hundred yards or earlier if you started to go down that hill with a battery that has been fully balance charged overnight.

I think it depends on what is the difference between the charging cut-off and overvoltage cut-off voltages on the BMS. Or wether the control board has a mechanism to better handle a situation like this. @esaj likely knows.

[palachzzz]

14 hours ago, meepmeepmayer said:

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.

It is slightly difficult to describe it with my poor english, but I will try:

When you are braking, FETs short one of motor winding for a short period of time, the motor winding turns into a coil of step-up DC-DC convertor, which accumulates braking energy, after that FETs disconnect coil from itself and connect*** to a battery, and accumulated coil energy flows to a battery. Coil short needed to increase generated voltage, otherwise it won't charge a battery.
It's basic principle of regeneration in electric transport.

***actually FET don't connect it to a battery, it is done by back Diodes built-in into FETs, but such description will help to understand proccess.

Edited September 4, 2018 by palachzzz

[Toshio Uemura]

7 hours ago, mrelwood said:

In my understanding you would be on your butt in a few hundred yards or earlier if you started to go down that hill with a battery that has been fully balance charged overnight.

I think it depends on what is the difference between the charging cut-off and overvoltage cut-off voltages on the BMS. Or wether the control board has a mechanism to better handle a situation like this. @esaj likely knows.

Now, I feel really lucky that I had forgotten my charger, when I visited 3 months ago on my Tesla and stayed over night. I had 70% battery left but I would have probably charged the wheel over night had I brought the charger. ?

[Steef Klonoa]

Thanks @mrelwood

[sb3en]

On 9/2/2018 at 10:28 AM, Arbolest said:

 

This is  interesting and brings up a valid point. But I think that what may be behind the weird braking issue is actually a lot simpler than many of us are assuming (Please, anyone with greater electrical knowledge feel free to strike this idea down, but do give a thorough explanation as to why ).

While it is true that a forward spinning motor like the type used in EUCs will generate a back-EMF as it rotates, which can be collected/stored for use later (regenerative braking), I feel like not enough attention is payed to the fact that this is NOT the only way that EUC's (and even most other electrically driven motors) slow themselves down. The simplest form of braking with these (and most types of) electric motors is simply to have the speed controller that's governing the motor's rotation run it backwards. I mean, instead of letting the siphoning off of the back-EMF cause the braking, the device just applies current in a cycle that opposes the motion of rotation. While no-where near as efficient in terms of power-savings (it saves zero power...In fact it uses even more ), this is WAY easier to implement.

I find it easiest to think of this form of braking as the controller pushing something (a wheel) to a stop, and I see regenerative braking more as letting the motor itself pull you to a stop...

I feel like Ninebot must have just done something like this for their braking routines instead of following along with the other EUC makers (no idea why though...). It may even help to explain why it feels so weak when trying to brake going downhill! Hear me out on this one:

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!

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...

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. 

If the Z10 is only braking directly and trying to push you to a stop, instead of boosting its effectiveness with regenerative braking and effectively pulling at the same time... It's going to have some problems, especially when compared to wheels that both push and pull simultaneously... 

If you think about the evidence of the Z10's handling on downhill braking. It feels as if it doesn't provide as much power/torque, BUT IT DOES. It's just that it's trying to fight your momentum with one hand (and leg) tied behind its back! This would make it feel MUCH weaker to us when comparing it to any other wheel because we're used to that great synergy (and amazing stopping power) that can be achieved if regenerative braking is implemented properly! The wheel is still giving us just as much power as it would in any other situation. The problem is that that's ALL it's giving us!

Sound's a bit silly, right? Why would Ninebot ever do something like this?!?! I think we need to ask... because if this is actually the case, then there's some work that needs to be done, and I do mean ASAP! 

 

Now see, this is intensely interesting to me! As soon as I read this, I immediately saw a problem with the fact that only ONE battery regained 20% of its capacity...  This shows that the system actually IS regenerating some power and storing it but... That means that the system as a whole only regenerated HALF as much capacity as the other equivalent wheel!?!? If it was really dumping ALL of the regenerative power (or as much as it didn't need to use elsewhere...) back into a single battery pack that only had half the total capacity of the system, then it should have jumped by 40%, right? 

What I mean numerically is simple (going to use nice round numbers for this):

If our two test wheels each have 1000wh capacities to start off with (a single 1000wh battery for the Tesla and 2 individual 500wh batteries for the Z10) , and both were run down to 600wh remaining by the time they made it to the top of the mountain (600wh for the Tesla and 300wh for each pack in the Z10), then everything is good and even. BUT, on the downhill run, if the Tesla regenerates back up to, say, 800wh remaining (20% capacity change) for 200wh of total regen, and the Z10 has its battery packs reporting at 300wh remaining (0% capacity change) and 400wh remaining (20% capacity change) for 100wh of total regen, then something is very wrong with that! 

First, it makes no sense to me why Ninebot would implement regenerative breaking, but only for half the system... And then what the heck is it doing with the rest of the power it's getting back from the motor?!?!

THIS CAN'T BE THE WHOLE STORY HERE!

 

I don't remember how the Z10 battery packs are connected together. If they are directly wired together then I agree with you. However, if they both plug into the control board, then I see no reason to assume that they would auto-balance. Especially if the board has some way of monitoring battery temperature or some other parameters that can help it make an informed decision as to which battery to pull the most current from at any given time. For example, let's say that one battery tends to heat up faster than the other... It would be more efficient (and safer) to draw a larger percentage of the needed current from the battery that tends to stay cooler.

 

 

*sigh* I almost would have been happier to hear that the system wasn't using any of the regenerative power at all, because then it would still be a straightforward, plain old mystery. Either that or that all of the power had been dumped back into the single pack which would have just indicated a balancing issue... But now I'm just confused, because those results mean that it's only regenerating at half the efficiency of the other wheels! What's going on here?! 

 

 

Didnt read any of it !

[Ziiten]

1 hour ago, sb3en said:

Didnt read any of it !

Didn't understand any of that.

[esaj]

18 hours ago, mrelwood said:

In my understanding you would be on your butt in a few hundred yards or earlier if you started to go down that hill with a battery that has been fully balance charged overnight.

I think it depends on what is the difference between the charging cut-off and overvoltage cut-off voltages on the BMS. Or wether the control board has a mechanism to better handle a situation like this. @esaj likely knows.

The overvoltage cut-off should only affect charging, AFAIK, the BMSs on all the brand wheels either don't have overvoltage protection on the discharge-side, or it must be set higher than 4.2V cell. Some might tilt-back or otherwise warn you if the voltage is too high, but shouldn't cut-out. But I don't know if anyone has tried to run a reaaaally long downhill straight off the charger, it might shutoff (or destroy your batteries) if the cells are kept at overvoltage for too long or the voltage reaches high enough number.

Some Germans (or at least German-speaking people) built a brake chopper(a circuitry that dissipates overvoltage during braking by dumping it through 2x 100W power LEDs or halogen bulbs) for KS16, that should take care to keep the voltage down, but requires some changes for other voltages than 67.2:

And even there you run the risk of burning the LEDs (halogen bulbs can take much more abuse) if they're kept on for long enough while and can't cool fast enough. The original circuit does have temperature-protection feature, so placing a temperature-sensor near the LEDs can be used to disable the chopper if the temperature goes too high (of course then all the braking energy is dumped to the battery during overvoltage).

Edited September 5, 2018 by esaj

[esaj]

Didn't read much of the braking conversation here otherwise, but I'd say @palachzzz's description is correct based on what I know. Better explanation here (for single-phase DC-motor, but the idea works the same for 3 phases):  https://electronics.stackexchange.com/questions/56186/how-can-i-implement-regenerative-braking-of-a-dc-motor   The answer to the question explains how the regenerative braking works and how it can pump up the voltage so that the current direction changes. 

It seems the wheels use, if not exclusively, at least most of the time plain regenerative braking. Other forms of braking electric motors exist (without separate mechanical brakes), but the problem is dumping the energy accumulated during braking as heat. AFAIK, the only sensible other way of braking an EUC besides regenerative would be "plugging", where the battery power is used to "try to run the motor in reverse", ie. the stator coils are switched so that they try to keep the rotor from turning ("pulling" the permanent magnets after they have passed the coil). The downside of that is that it burns off even more energy as heat in the motor and mosfets.

Edited September 5, 2018 by esaj

[Rehab1]

20 hours ago, Toshio Uemura said:

What kind of hills are we talking here? This kind? 

 

Nice! No grass to mow. 

[mrelwood]

3 hours ago, esaj said:

The overvoltage cut-off should only affect charging, AFAIK, the BMSs on all the brand wheels either don't have overvoltage protection on the discharge-side, or it must be set higher than 4.2V cell. 

I seem to be wrong here, but I had understood that there indeed is a voltage at which the BMS (or the wheel itself) shuts down thinking it’s power source is damaged or of the wrong type. The limit could be 4.35V, or could be quite a bit higher.

This calls out for a test! I wonder if someone here has a separate BMS, a large enough power source, and a bit of time...? 

[esaj]

11 minutes ago, mrelwood said:

I seem to be wrong here, but I had understood that there indeed is a voltage at which the BMS (or the wheel itself) shuts down thinking it’s power source is damaged or of the wrong type. The limit could be 4.35V, or could be quite a bit higher.

I don't know for sure anything else except that my rides start with a downhill everytime, and I've taken both KS16's, the generic and the Firewheel down that hill "hot off the charger" after a full balancing charge, none of them have ever cutout due to overcharge (although likely they've all been overcharged slightly on that downhill on many occasions) with the original packs. Only time that caused a cut-off was with the custom packs that had a wrong type of BMS (using the same protections on both charge & discharge). Yes, it sucked, although luckily I didn't fall but managed to land on my feet and keep running when the wheel shot out from under me.

 

Quote

This calls out for a test! I wonder if someone here has a separate BMS, a large enough power source, and a bit of time...? 

I don't have a separate BMS currently, I shipped the packs to have the BMSs exchanged to ones I bought from 1RadWerkstatt by the guy who built them (he runs his own company, which among other things, builds custom Li-ion batteries, mostly for diving equipment) and said he can keep the "wrong" BMSs. I'd have to tear down a pack to get the BMS, unlikely to do it before my trip at least.

Edited September 5, 2018 by esaj

[mrelwood]

3 hours ago, esaj said:

my rides start with a downhill everytime

How long and how steep is the hill? Do you get warning beeps from the wheels?

When I stopped with what I consider to be a medium powered braking from 30km/h after riding only a few hundred metres at level ground, I always got a warning beep from the 16S.

[esaj]

41 minutes ago, mrelwood said:

How long and how steep is the hill? Do you get warning beeps from the wheels?

Firewheel or the generic didn't have warnings (or then I never noticed them) for overcharge, but the KS's would beep if going down faster and then braking stronger with full battery. A quick glance on height maps says it rises about 10 meters vertically in about 110 meters of horizontal travel, so not particularly steep (about 9%, if I calculated correctly, the steepest bikelane around here is a long uphill one at the edge of the town with parts going up to 18%). The asphalt is cracked and there are lots of bumps in the road caused by ground frost, so I don't usually ride it down very fast anyway.

 

Edited September 5, 2018 by esaj

[Marty Backe]

I took the Z10 to Palos Verdes / Redondo Beach, in Southern California for some trail riding and a little tour of the Redondo Beach Pier. The Z10 sure is a new wheel for riding in sand and soft terrain.