Anyone Ever Experience a Braking Failure Going Down a Steep Hill?

[Hunka Hunka Burning Love]

My Ninebot One E+ hasn't let me down ever since I bought it, but on some of these crazy steep hills I'm braking while going down often scare me a bit.  I still have to buy a tether.  I don't overspeed going down a hill as that is surely a one way ticket to faceplantville, but even at regular under 22 kph speeds, I wonder what would happen if suddenly something shuts down or overheats?  I'm guessing I would fall backwards while the wheel shoots forwards down the hill.

Do the MOSFET stay relatively cool when doing controlled, prolonged descents?  Except in a full battery overcharge condition, would you ever expect a wheel to fail while going slowly down a hill?  Does the steepness of the grade have any effect on heat produced at the controller or BMS?  I guess that if a MOSFET fails the wheel would likely have increased resistance to rolling so it wouldn't just free wheel down the hill?  It might go tumbling, but the back EMF should resist the wheel from spinning freely almost like a built-in emergency failure brake?

[Frode]

44 minutes ago, HunkaHunkaBurningLove said:

but the back EMF should resist the wheel from spinning freely almost like a built-in emergency failure brake?

Only if current flows. The energy from breaking must be consumed for breaking to occur, for example by current going back into the batteries or being "coocked" (i.e.transformed to heat) in a resistance. No current, no breaking

[HEC]

1 hour ago, HunkaHunkaBurningLove said:

I'm guessing I would fall backwards while the wheel shoots forwards down the hill.

I'd say you'll still most likely fall face front / down ... mainly due to your forward momentum / inertia.

[Hunka Hunka Burning Love]

I guess it just feels like you're leaning back because the contact patch has moved position to the back area more on a downhill.  I wonder if the unit angle is actually still tilted forwards or if it's actually tilted back as well?  In any case, I'm glad that there aren't many reports of this happening.  Whenever I see people down the hill that I'm descending, I wonder what would happen if I lost control or the power cut out for whatever reason.  I definitely need to get a tether.

I also had a chance to tackle an extremely high hill on gravel which was a challenge.  I didn't think I was going to make it as it was crazy steep, but surprisingly the Ninebot came through which was a great relief.  I'll have to take a photo of the hill if I decide to try that again.  Loose gravel is the worst!  Just doing a turn at speed on level ground with loose gravel, I felt the wheel sliding laterally a la EUC Extreme style, but I was able to recover and keep going.

[dmethvin]

I had a BMS cutout due to a bad battery pack a year ago while going downhill at less than 10mph. I was leaning back to brake and it just freewheeled out from under me. I pretty much landed on my feet with no problem. I think cutouts while you're leaning back are easier to recover from than leaning forward, it just seems like your posture is better for staying on your feet since once they hit the ground your momentum is still carrying you forward and tends to push your feet back under you.

[Chriull]

3 hours ago, HunkaHunkaBurningLove said:

My Ninebot One E+ hasn't let me down ever since I bought it, but on some of these crazy steep hills I'm braking while going down often scare me a bit.  I still have to buy a tether.  I don't overspeed going down a hill as that is surely a one way ticket to faceplantville, but even at regular under 22 kph speeds, I wonder what would happen if suddenly something shuts down or overheats?  

With an iphone and 9bmetrics you could log the behaviour and see how much the ninebot gets stressed.

3 hours ago, HunkaHunkaBurningLove said:

I'm guessing I would fall backwards while the wheel shoots forwards down the hill.

The wheel will be definitely "freewheeling" - hopefully it happens as @dmethvinreported and one has a better chance to stand it....

3 hours ago, HunkaHunkaBurningLove said:

Do the MOSFET stay relatively cool when doing controlled, prolonged descents?  Except in a full battery overcharge condition, would you ever expect a wheel to fail while going slowly down a hill?  Does the steepness of the grade have any effect on heat produced at the controller or BMS?

Again best answered by 9bmetric logs... Theoretically/imho the steeper the decline the more the wheel has to brake == more current and so more power dissipation for the mosfets...

3 hours ago, HunkaHunkaBurningLove said:

  I guess that if a MOSFET fails the wheel would likely have increased resistance to rolling so it wouldn't just free wheel down the hill?  It might go tumbling, but the back EMF should resist the wheel from spinning freely almost like a built-in emergency failure brake?

Failed mosfet's where till now reported as short circuit for the motor coils, which leads to a quite abrupt stop and presumably a faceplant...

[Rehab1]

@HunkaHunkaBurningLove Oh how I hate gravel roads especially turning! I also hate talking about face plants!!  Yes take a picture of this treacherous hill. Well at least you gained some additional somatosensory inputs that may come in handy someday. Before long you'll be riding up sand dunes?

[Hunka Hunka Burning Love]

If it ever stops raining here I'll have to give it another go!  I did roll past a couple of bewildered park workers who waved back and said hi.  I was worried they were going to kick me out of the park or give me a fine, but I think they were more puzzled by what I was riding more than anything.  It's nice that these EUCs look like a gliding single wheel without a motor so I think some authorities don't know if it's powered or not!  I went by really slowly past them showing that I'm not tearing up the walking/bike paths and terrorizing people.  I'll have to practice my fake skateboard kick push to confuse them a bit more...    I think bicyclists are more of a hazard in these parks as they are constantly zooming past a high speed past pedestrians.  I always pass people at barely faster than walking speed to try to avoid startling anyone.  After checking that I'm clear then I speed up.  That way it gives them a good chance to take a peek at what I'm riding and briefly chat if they have a comment.

I've got too many things installed on my iPhone to unjailbreak it.  I don't bother with cracked apps, but it's mainly to be able to use Kodi on my phone.  I'd likely have to wipe it and upgrade to the next IOS just to get 9Bmetrics going.  I'm curious about the current and voltage spikes, but maybe not that curious as to mess with my phone setup for the time being.

[Keith]

First Rule of thumb with any wheel (IMHO) is don't go down any hill that is steeper than the wheel can go up as maximum braking down will be similar to maximum power up.

Having said that, going up hill you have wind, friction and gravity all working against you and consuming power. Going down hill wind and friction are assisting in slowing you down. 

I think, therefore, it is unlikely that heat will be a bigger problem going down hill than up. Currently, the only way I am aware of to consume that braking power is by regenerating energy into the battery so any failure is likely to be due to either the battery becoming fully charged or the back EMF voltage exceeding the acceptable battery charge voltage, going slowly will help the latter.

As far as I can tell, a braking failure resulted in my only faceplant, and on the flat! Accelerating to maximum speed (showing off) with a fully charged battery I immediately, but not aggressively, leaned back to slow down again the peddles suddenly went "floppy", strangely enough I came off forwards not backwards. I tend now to use the excellent chargedoctor and stop the charge when it drops to 1 amp unless I have a long ride ahead, that ensures some braking headroom. Took me weeks and weeks to creep back up to beeping speed again though.

[OliverH]

From my experience: Going downhill stresses the MOSFETs also. I had run a KS18 in heatprotection downhill. Controlled soft, than hard tilt back, slow down, stands still with hard tilt back till cool down.

If the motor can't handle the cintetic energy he'll slip or doing a cut off. Remember there's a cut off point 30 degree for and backwards of the shell. I've seen people (light weight) doing downhill fast and braking hard with no problem. A couple of kg more would have been resulted in a faceplant.

[The Fat Unicyclist]

I live on a fair sized hill, so I am experimenting with this daily... And while I haven't worked it the detail yet, I observe both regenerative and degenerative braking - depending on speed and steepness...

[Pingouin]

Hi,

I went up a montain on a 5km road going up with a 4 to 8° angle, then I came down, didn't have any issue, I was going up at 14kph, and down at 19kph average, with a fully charged battery. (about 500m height difference)

I checked the temperature at the top of the montain just after the climb, it was 62°C, and 47°C when arriving at the bottom. I think it's doable if you don't go too fast.

[electric_vehicle_lover]

I think the BMS can cut off for excess of voltage when braking/regen. Also if temperature gets higher some value.

The board can also cut for excess of voltage of battery when braking/regen.

The MicroWorks 30B4 board doesn't cut off for excess of temperature but will beep and slow tilt back the pedals so it is safe.

I don't know of more conditions for a cut off.

[Hunka Hunka Burning Love]

I suppose the risk of "over braking" is then greater going down a steep hill. People have managed to fry their controller boards during an emergency brake.  Going down a hill, if you brake too quickly that might spike the regenerative current too high for the board to handle I'm guessing?  I gotta unjailbreak my phone and get that 9botmetrics app working... When is the android version coming out?  I just got a new to me LG G3 that I'm dying to use...

[EUC Extreme]

 

"

Anyone Ever Experience a Braking Failure Going Down a Steep Hill?"

 

Every time when I'm driving

 

[Hunka Hunka Burning Love]

Well it's pretty difficult to brake in mid-air going over a hill at high speed so I'm not surprised!  Not everyone gets as much airtime as you do.  Some of us like going at our granny speeds for safety.  

Now if Ninebot would get their heads out of their hindquarters with ticking off their loyal distributors and get on with developing the next Ninebot 16" wheel that is lightweight, capable of 45 kph cruising speeds, and is super reliable they might not lose as much market share to their competitors, and I would have some reason to stick with the Ninebot brand.  My NBOne E+ is slow, but it is so reliable going up and down hills that I really can't complain much about it.  It's slow and steady, but it might not win any races.    If InMotion proves to be just as reliable, they are going to be real winners in the end.

[Gimlet]

The big problem with going down hill is that momentum builds up very quickly and added to gravity it can easily overcome the braking ability of the motor on hills that the wheel is quite capable of climbing.

I've had more seat drops from wheels running of ahead in freewheel than step offs or crashes and now treat downhill stretches with great respect, even resorting to slalom techniques on some of the steeper ones.

[MarkoMarjamaa]

1 hour ago, Gimlet said:

The big problem with going down hill is that momentum builds up very quickly and added to gravity it can easily overcome the braking ability of the motor on hills that the wheel is quite capable of climbing.

I've had more seat drops from wheels running of ahead in freewheel than step offs or crashes and now treat downhill stretches with great respect, even resorting to slalom techniques on some of the steeper ones.

If I don't feel confident about the slope, I just slalom. Going up or going down.

[Keith]

@Gimlet that is very very good point. Allowing the wheel to speed up down hill is certainly a very real danger, although tilt back and beeping should happen on most wheels it probably will not feel as discouraging to the rider as on the flat as you are tilting back anyway against the slope and speed could easily increase to the point where there is not enough torque to balance the wheel - let alone brake! Although not specifically a hill, In the below thread the rider states the log showed 46kph, lift shut off speed is around 45kph so it is hardly surprising the wheel shut down, just not funny that the EUC will run to 40kph with so little overhead.

So there are a choice of failures available if you let the wheel gather too much speed down hill.

• tilting back too far until wheel thinks it's fallen and shuts down
• exceeding shutdown speed
• running out of torque
• Back EMF too high and over stressing components
• unable to brake enough to prevent wheel speed increasing further
• Battery full so nowhere for current to go
• overheating.

Slaloming is certainly a tactic to keep in your head if you do find the wheel getting away from you (or even turning sideways if there is room) that dumps the energy into the tire instead of the electrics.

 

[The Fat Unicyclist]

If I was to stop on a hill, it would use power (to stay in one position).

So,  the closer I come to stopping, the less likely it is to be generating power.

So, harder braking is better???

[Hunka Hunka Burning Love]

I would think your first two statements are correct.  The last statement I think might be troublesome.  I once drove a very heavy vehicle down an extremely steep downgrade.  I kept the speeds slow, but braking was tremendously harder to do even in low gear.

I think with our EUCs it might be wiser to keep the speeds moderate and controlled, and avoid hard, sudden braking if at all possible as on a downward slope the forces on the wheel are greater than on a flat road.  The wheel has to brake against the rider's weight along with the forces of gravity acting on it down the slope.. The wheel doesn't know the angle it is riding on of course, but there is an increased load on it as if your weight has increased all of a sudden (apparent weight).

[The Fat Unicyclist]

I definitely agree - hard braking adds a risk of injury that should be avoided. 

But is there a benefit in varying the amount of braking (more and less) to alternate between draining and charging the battery, reducing the chance of an overcharge cutout? 

Assuming of course that we know when the braking is draining or charging. 

[HEC]

2 hours ago, HunkaHunkaBurningLove said:

The wheel doesn't know the angle it is riding on of course

While that's true with most (if not all) of the current controller board designs (as @esaj can confirm) due to having MPU's gyro and accelerometer outputs connected together nothing stops designers of the wheel / programmers of the firmware to use the accelerator outputs separatelly (or even adding secondary MPU just for this purpose) and detect asscend or descend of the wheel as well.

[Hunka Hunka Burning Love]

57 minutes ago, The Fat Unicyclist said:

I definitely agree - hard braking adds a risk of injury that should be avoided. 

But is there a benefit in varying the amount of braking (more and less) to alternate between draining and charging the battery, reducing the chance of an overcharge cutout? 

Assuming of course that we know when the braking is draining or charging. 

That's a very good question! Should one be steadily "riding the brakes" on an EUC going down a long, steep hill or vary things with speeding up and braking, speeding up and braking, etc?  

With cars I see people riding their brakes, and I often wonder how long their pads are going to last doing that as they heat up and possibly glaze over. 

It would be interesting to see a Wheelmetrics or 9botmetrics graph with temperature readings to see what is happening.

With my iPhone it seems to be able to detect and record altitude and grades so EUCs should be able to as well, but I wonder if that information would be useful to the wheel operating system.  I remember we touched upon different sensors and methods to do so, but how would the extra information change the riding characteristics and behaviour of the wheel I wonder?

[Alien Rides]

I live and ride around the steep hills of San Francisco. I've been able to make it up pretty much any hill I've tried, although at a very slow speed, around the same speed as a grandma inching up a hill. Most of my wheels are able to make it to the top no problem, but some have overheat issues. I've never had a problem with batteries cutting out, or overheating going down though. I typically descend pretty slowly, and avoid sudden breaking when going downhill.