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Story of me learning, riding and falling off an Inmotion V8


Ubeogesh
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Hy and welcome to the Forum! Perhaps not the nicest Story to start with....

I wish you a good and completly healing!!!

I dont know how far you investigated into EUC's in General....but what happends to you -or better your wheel- is nothing Special!

You just overpowered it (pushing to hard to fast to 25kmh on a somewhat steep hill) ....the fact that your Batterie was only at 50% CAN made the Point that it gave up.....but if the hill was steeper or the Speed would be higher, this also could happen at a higher Batterie percentage Level!

 

Each EUC has it's Limits!!! A Point where they can not deliver anymore torque/power...and ALL EUC's do the same on this Point: They CutOff, and just stop working from one second to the other! Some EUC's might have a warning like ("Caution Overpower" or warning beeps)...but if you push to hard and much to fast, it is even to late for them to warn you and the Cutout happens before warning.

It's not that bad, that this has happend on a V8....as some People think the V8 is "safe" and did not have such Cutouts.....you (and others in other threads) are the proof that this can happen to this wheel also!

I can only advice you think about that helmet Thing again! When a real cutout happens, it is pure luck how you land! You were just lucky that your Hands broke first and they were in the way.....there are Pictures Floating around where People even smashed their complete Face...and believe me, on a unexspected Cutout "running away" from the wheel is not possible anymore, especially over 15kmh....

I have -until today- about 5 broken rips....and know for sure that each fall could hit my head also! So...if you want to Keep on with your riding style (fast accelerations and higer Speed) i can only warn to drive without security gear.....

Edited by KingSong69
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Hi KingSong69, thanks for the kind reply and the welcome! I knew that "cut outs" are a thing, but I was stupid enough to think I got it under control :) Thanks for the warnings, you've leaned me more towards getting a helmet.

As for the cutout warnings, I don't remember having any of them. Just the warnings about reaching max speed.

32 minutes ago, KingSong69 said:

I have -until today- about 5 broken rips...

You mean ribs, right? That was at once, or in several crashes? How could you fall on a rib...?

By the way, I think it might be interesting to make a "EUC injuries megathread" on this forum... or is there one already?

Edited by Ubeogesh
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Interesting story, and get better soon.

With your weight and accelerating up a hill at 25 km/h, it's normal that the wheel could not keep up. That's just the limit of the V8's 800W nominal motor. You'd need a stronger motor wheel like the 16S (1200W) or ACM (1500W) or whatever to do that safely enough. So don't do it again (wheels lose almost all torque at max speed, so go slower on hills):) Also be aware the same applies to braking, so if you had tried to brake going down that hill as much/fast as you accelerated up, you'd have fallen too.

Also, helmet really is the second most important thing after wrist guards (or maybe the most important). If the wheel cuts out (instantly stops working) due to hardware failure or you overpower it (what you did, and what essentially is like a slow cut out), you simply get rotated into the ground (really fast in case of a real cut out). So ideally, face protection, but as not many people like a full face helmet (me included), a regular helmet protects at least the (most important) rest of the head. Helmet also works if you fall on something, like a curb, post, car, whatever. Here's a nice picture of a dented helmet from a car bumper, could have been the skull itself: click.

Edited by meepmeepmayer
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3 minutes ago, meepmeepmayer said:

With your weight and accelerating up a hill at 25 km/h, it's normal that the wheel could not keep up. That's just the limit of the V8's 800W nominal motor. You'd need a stronger motor wheel like the 16S (1200W) or ACM (1500W) or whatever to do that safely enough.

I'd rather loose some weight lol. Being unable to properly feed myself for almost a month gave me a good start already :)

Also, how do you know power to human weight ratio? I was told that the V8 is good enough up to ~120 kg... but I guess that is for slow riding.

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Just now, Ubeogesh said:

I was told that the V8 is good enough up to ~120 kg... but I guess that is for slow riding.

 In general it is good enough but you must consider there is no margin for error with these devices. Any vehicle will be less responsive accelerating up a hill. Most just have reduced acceleration and you forget about it. On a unicycle it results in an overlean and faceplant. Any wheel will do the same given the right condition.  There is some expectation that the rider will temper their expectations during adverse conditions which you are learning now.

The V8 is a mid level wheel. As already mentioned if you want to push things hard you'll need to look at a KS 16S or mSuper with bigger motors and larger battery packs.

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Yea losing weight is a great idea:D though it should be by choice...

You know a wheel can't do something if it can't do it and crashes you:P Pretty much the only thing that is reliable. From experience (posts here, like yours, so thanks!), it seems <1000W nominal (V8 is 800W nominal) means "think about what this thing can do" and >1000W or 1200W or 1500W means "really hard to overlean unless you're trying hard or are really fat".

The hill wasn't the problem, the speed was. 25 km/h is not too far from the max speed on flat ground, and wheels lose torque the closer they get to their max speed. There's a nice diagram that @Chriull likes to post (see here), basically torque (= the ability to keep you balanced) goes towards 0 when you approach the max speed.

120kg is theoretical, you can go 15 km/h safely on the V8 (I guess, no idea) but I would not go faster than this at 120. I think 90kg is the max weight I would recommend a V8 to anyone.

Edited by meepmeepmayer
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7 minutes ago, meepmeepmayer said:

From experience (posts here, like yours, so thanks!),

Don't forget that mine had around 50% charge at that time. That day I started at around 80%... this is another lesson for me - don't be lazy and always fully charge it.

 

7 minutes ago, meepmeepmayer said:

Yea losing weight is a great idea:D though it should be by choice...

P.S. It is by choice, it was just so hard to stop eating pizzas every weekend :) Now that I see progress, I am much more motivated.

Edited by Ubeogesh
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15 minutes ago, meepmeepmayer said:

 

The hill wasn't the problem, the speed was. 25 km/h is not too far from the max speed on flat ground, and wheels lose torque the closer they get to their max speed. There's a nice diagram that @Chriull likes to post (see here), basically torque (= the ability to keep you balanced) goes towards 0 when you approach the max speed.

This. So this. So so very much this.

I'll bet if you fired up WheelLog then it would show mostly between 200-600 even up hills with the occasional 1000 watt + spike.

I have been wondering, if wheels had some sort of magical gearing that allowed you to go from direct drive into presumably second gear, then would that torque curve then shift to the right (higher speed)?

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22 minutes ago, Ubeogesh said:

Don't forget that mine had around 50% charge at that time. That day I started at around 80%... this is another lesson for me - don't be lazy and always fully charge it.

Howdy,  From reading other threads it looks like going downhill with a fully charged battery is almost as dangerous as going uphill with a partially charged battery.  The regenerative breaking from going downhill will attempt to overcharge the battery, and then the wheel will shut down.  Preventing downhill cutouts is one of the benefits of the 80% charge guideline.

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3 minutes ago, Code In Space said:

Howdy,  From reading other threads it looks like going downhill with a fully charged battery is almost as dangerous as going uphill with a partially charged battery.  The regenerative breaking from going downhill will attempt to overcharge the battery, and then the wheel will shut down.  Preventing downhill cutouts is one of the benefits of the 80% charge guideline.

I didn't follow any guide lol. I just didn't charge it after previous days small ride.

I had no idea wheels regenerate power on downhills... do all of them do this? Are they not smart enough to not overcharge at the same time?

Also, 80% seems like too much... I imagine charging is supposed to slow down after 90%, so do you really think a downhill could charge like 10%?

80% seems way too little for me... Ride to work an back takes away like 40-45% of the charge for me.

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Howdy,  This is one of those things that is hideously complex.  Much more complex than can be explained with a simple percentage charge.  It has to do with how much current the battery can deliver uphill and how much current it can absorb downhill.  Regenerative braking generates a lot of current.  Someone that really knows more about batteries that I do will need to fill in the details.

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4 minutes ago, Code In Space said:

Howdy,  This is one of those things that is hideously complex.  Much more complex than can be explained with a simple percentage charge.  It has to do with how much current the battery can deliver uphill and how much current it can absorb downhill.  Regenerative braking generates a lot of current.  Someone that really knows more about batteries that I do will need to fill in the details.

I just searched a bit about this. Figured it's a "natural" thing of electric motors, rather than an intentional feature. However if this is indeed an issue, how come EUC manufactures haven't addressed it?

In any case... none of my rides start from a downhill... rather an fast horizontal swoop followed by an uphill. But this is a good thing to keep in mind, so thanks!

Edited by Ubeogesh
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Wheels must have regenerative braking. If you need little to no power (downhill) but the magnets spin, they induce an electric current and that has to go somewhere (charge the batteries).

How much energy you get back depends on riding style, speed etc.

All you need to do is not charge to 100% and start on top of a hill. Otherwise, the wheel should warn you of overcharge and hopefully overcharge the batteries a little (which is possible) instead of instantly cutting off (never heard that, as long as you stop after the first warning you should be good).

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An excellent question, and one that I can not begin to answer.

If you want to go down the rabbit hole with batteries you can start with this thread:

http://forum.electricunicycle.org/topic/7614-battery-capacity-longevity-and-manufacturer-reserves/

In it @WARPed1701D mentions Battery University (batteryuniversity.com) as a good resource.

 

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2 hours ago, Ubeogesh said:

You mean ribs, right? That was at once, or in several crashes? How could you fall on a rib...?

Yip, sorry, my english :-)

That is from two different crashes...one self overconfidence...one a cutout on a hill!.....on both i fall on the side, with my arm laying on the side(no chance to turn the arm/hands up fast enough)... and as the arm was laying on this side where i fall, my arm literally broke my rips...the arm only received some bruises!

But like said, both crashes could have lead to much worth injuries....just imagine a curb stone is in the near of a fall, very easy to have a cracked head, also!

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32 minutes ago, Ubeogesh said:

I didn't follow any guide lol. I just didn't charge it after previous days small ride.

I had no idea wheels regenerate power on downhills... do all of them do this? Are they not smart enough to not overcharge at the same time?

Also, 80% seems like too much... I imagine charging is supposed to slow down after 90%, so do you really think a downhill could charge like 10%?

80% seems way too little for me... Ride to work an back takes away like 40-45% of the charge for me.

The 80% charge "guideline" is more meaning for not charging always to 100%  for longevity , then you have longer batterie life....and more cycles of loadiing before the batterie gets weaker....but really, thats a different  thing and a normal user doont have  to worry about lifetime of batteries....

 

If your rides start with a Very long downhill....90-95%charge should be totally fine!You also get a voice/beep warning before a overcharge cutout will come! enough time to slow down! The energie has to go somewhere, so no!, the wheel is not able to handle that more "intelligent"....

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  • 1 month later...
On 04/07/2017 at 5:17 PM, KingSong69 said:

If your rides start with a Very long downhill....90-95%charge should be totally fine!You also get a voice/beep warning before a overcharge cutout will come! enough time to slow down! The energie has to go somewhere, so no!, the wheel is not able to handle that more "intelligent"....

They could have it consume the excess power. It could generate heat, lighting, .... 

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On 04/07/2017 at 3:00 PM, Ubeogesh said:

As for the cutout warnings, I don't remember having any of them. Just the warnings about reaching max speed.

How are they different? My hunch is that you didn't have a cutout but an overlean. That is, you may have heard an overload warning. That is, the motor didn't shut down and stop working, but it was too weak to keep supporting you. 

The maximal torque a wheel can deliver goes linearly down with increasing speed and reaches zero at the (theoretical) max speed of the motor.^1 This has nothing to do with battery, just the motor. In the free running experiment, I see a speed of 42km/h for the V8. So I would estimate the max speed around 50-55km/h, anyone has some specific information on that?

This means, at 25km/h the wheel has about half of its maximal torque of zero speed. Leaning in ~100kg at this speed might just about be too much to ask for.

The most important lesson to learn is IMHO to lean in (and drive) more carefully in particular above 15km/h-or-so, always. Protection gear may help, but is IMHO less important.

motorcurve.gif

Torque, power, and efficiency versus speed of the theoretical model of the motor.

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2 hours ago, ir_fuel said:

They could have it consume the excess power. It could generate heat, lighting, ...

If the motor is nominally (say) 800W with peak over 2400 W then potentially you could be talking about regenerative braking generating similar amounts of power when decelerating, even if it is not very efficient this could be getting close to 1KW in some situations. That is not a trivial amount of heat to try to get rid of and it needs to be electronically controlled as it is still part of the force that is balancing you. Feeding it back into the battery is the simplest way to produce the required braking force under full control.

In practice, as I understand it, it is the voltage peaks, rather than current, that regenerative braking can cause that are the real problem with a full(ish) battery. I.e. You can ride uphill for a kilometre and still have overvoltage issues riding back down hill. This is because the nearer the battery is to full the less it is able to sink this regenerative energy (and thus pull the voltage down) and that can result in the voltage rising above the safe maximum for the battery, even though it isn't full.

Edited by Keith
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I will make the experiment the next time my battery is fully charged (doesn't happen very often). I just wonder whether I should try hard braking or soft braking to begin with. Hard braking is anyway non-generative, AFAICS. That is, a very smart controller could switch away from regenerative braking when the battery is full. Of course, non-generative braking is only possible for a comparatively short period of time until overheating.

Edited by Mono
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4 hours ago, ir_fuel said:

Why?

Why it is: because regen braking is limited in the amount of deceleration it can produce, because the allowed charge current for the battery is comparatively low.

Why do I think it is: collected wisdom from a bunch of forum threads and looking at the voltage and wattage changes during braking and I can even feel when my Gotway MCM2s switches from regen to power braking, aligning with the data. I don't have the time right now to dig out the threads, there are quite a few of them, including rather controversial discussions. 

Googling

   regenerative or power braking site:http://forum.electricunicycle.org

or any subset could be a good start. 

Edited by Mono
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