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Greetings, um... electric unicyclists.  (Is there a better name?  Cycleers?  Cyclnauts?)  I have made the decision to venture into this strange, unfamiliar land within the next two months.  Although I will likely start with a smaller wheel, I plan to eventually move to use of a Gotway EUC.  Once I have graduated to their use, I plan on owning both a 14` and 18` Gotway, both for urban and off-road use (including tricking), though I'll start off with the 18` since my training EUC will likely be ~14`.  I have many questions related to this significant expenditure, however, before I made the dive.  So, my questions are mostly about the Mspeed 18`.

And yes, I know the MkIII is releasing sometime this year.  Thanks for beta testing it for me, but I want to go with a tried and proven off-road model, at least until I find out that there's a V Speed model for the MkIII.

1.  Theoretically, since the system has regenerative braking, wouldn't it be possible to recharge the battery by turning the wheel off and pushing it with the trolley handle?
2.  Has anyone successfully found a way to safely get 12v/5v from the battery?  I'm especially interested in at least USB.  Any resources on how to do this properly?
3.  Has anyone found a better tyre than the stock one?  I'm looking for a good off-road one.  A good 18" with a 2.5" width is good, right?  Has anyone tested a wider tyre?
4.  I need to maximize my battery capacity.  I'm guessing that no one's yet beat 1Rad Werkstatt's 1035 KWh deal?
5.  Any recommendations for a saddle?  As in, how they're usually made, of what material, etc?
6.  Do we know the maximum load?  I won't be putting more than 75kg on it, but just in case.
7.  Surely there are examples of EUCs failing, like broken pedals or something?

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1. yes

2. some wheels have it as standard (ks, gotway mcm4), you can also make one yourself using a dc-dc voltage converer, couple of bucks from dx.com

3. i guess they're hard to find

4. why would you need so much? planning to ride for many hours in one go? you can make custom batteries, cheapest option

5. apparently not many people want to sit on their electric unicycle, not many saddle mods around

6. hard to answer, there are people 120kg+ riding with success, but at cost of performance

7. unicycles shutting down unexpectedly is the main worry, several reasons for this, loads of posts on this forum on the topic

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1. The wheel needs to be turned on for any charging to occur, the half-bridges won't conduct if the wheel isn't turned on, and thus there's no connection between the motor and the batteries, plus it's not that simple, ie. just connecting a 3-phase motor to a battery and turning it won't work, it needs to charge the motor coils and then shoot off the excess energy to the battery, and repeat it fast as the motor turns. Here's a more detailed fairly good (although only with a 1-phase motor) explanation of how it works: http://electronics.stackexchange.com/a/56187

You're unlikely to get much charge from just pushing it around, there isn't much power involved in that.

2. You could use a step-down transformer (buck converter) for this, just make sure it can handle the full voltage of the EUC battery (67.2V or so), most cheap ones I've seen are limited to 35V max.

3. Don't know about these, probably at least one person to ask is @vee73

4. I don't know of any higher capacity batteries than the >1kWh battery done by @1RadWerkstatt available for MSuper. You could build a battery yourself, but you need some special tools and it can be dangerous if you don't know what you're doing.

5. Don't know about this, if the plastic frame is sturdy enough to support your weight, I guess you could tape a pillow on top of it? :D 

6. I think 120kg is what most manufacturers state, although at least the smaller motors/batteries will probably be struggling with that much weight. I wouldn't expect any problems powerwise with 75kg and a powerhouse like MSuper with 1000W motor.

7. Unexpected shutdowns are more or less common, although many times it's the rider making some mistake (overleaning / overspeeding), or riding with too empty battery (especially in cold conditions). I recommend using full set of protective gear at all times, there's always the chance that something breaks unexpectedly.

I don't recall anyone saying that their pedals have broken, but there have been numerous blown mainboards (mostly Ninebots, due to faulty firmware ;)), especially the motor drive bridges, broken batteries (faulty cells or faulty BMS) and while the shells can usually take quite a beating, they can crack with hard enough hit or over time with wear & tear of multiple crashes. The motors themselves and pedals seem to be fairly robust, usually if there's a problem with the motor, it's a loose hall-sensor.

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Rough figures 18x2.50 size tire is really hard to find.
I have found only two good model. They, too, are only available in China.
The second is a slightly lower figure, while the rubber is lighter.
This is good if you drive at high speed. But if you do not drive continuously at full speed, the heavier is good. However, its availability has been recently really bad.
Neither model is perfectly suitable for such terrain.
But a little cutting, the pattern is done in really rough.
Although this ..

14078527.t.jpg

 

EDIT:

The problem is that the rings can be found only in Taobao to.
From there, you can not order from the Chinese.
Somebody has to buy it from there, and send.

 

 

 

 

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28 minutes ago, esaj said:

1. The wheel needs to be turned on for any charging to occur, the half-bridges won't conduct if the wheel isn't turned on, and thus there's no connection between the motor and the batteries, plus it's not that simple, ie. just connecting a 3-phase motor to a battery and turning it won't work, it needs to charge the motor coils and then shoot off the excess energy to the battery, and repeat it fast as the motor turns. Here's a more detailed fairly good (although only with a 1-phase motor) explanation of how it works: http://electronics.stackexchange.com/a/56187

You're unlikely to get much charge from just pushing it around, there isn't much power involved in that.

@esaj: But there is some amount of energy to be captured from pushing it, right?  Particularly, if the braking system primarily does it's charging when going downhill, and since it's only powered on for the use of self-balancing, not propulsion, then there must be a way of replicating that action while on a flat road, even if it's not much energy to be collected?

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10 minutes ago, pArmitage said:

@esaj: But there is some amount of energy to be captured from pushing it, right?  Particularly, if the braking system primarily does it's charging when going downhill, and since it's only powered on for the use of self-balancing, not propulsion, then there must be a way of replicating that action while on a flat road, even if it's not much energy to be collected?

Yes, probably you will get a little charge from that, but not much (ie. you'd have to push it for a loong, long time to fully charge it from almost empty ;)). And as the wheel has to be turned on at the same time, it will also use some power to stabilize itself (but not much, few tens of watts maybe?). The question then is, if the charge got from pushing is more than what it is using at the same time (maybe, but I still I won't expect it to be much).

If you tilt the wheel even slightly forwards when pushing it with the trolley handle, it's actually using power, as the motor is being run to return to the upright position, so you'd need to either keep it fully upright or slightly tilted backwards in regards to the direction you're pushing it.

EDIT: Actually, thinking further, there might be a minimum speed required to charge, as the voltage from the motor towards the batteries has to be larger than the battery voltage for the current to run from motor to battery.

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Quote from Wikipedia:

"When considering human-powered equipment, a healthy human can produce about 1.2 hp briefly (see orders of magnitude) and sustain about 0.1 hp indefinitely; trained athletes can manage up to about 2.5 hp briefly and 0.3 hp for a period of several hours."

So one horsepower is 746 watts. 0.3hp would be 224W. If the regenerative braking was 100% efficient and if charging was 100% efficient and if you could maintain 0.3hp whilst pushing fast enough (as @esajmentions) to generate a voltage greater than the existing battery voltage and if the wheel being powered up took negligible power itself then you could charge a 224Wh battery in an hour. They are really big "If's". Charging seems to be in the order of 70% efficient (based on charging at 1/10th C (for example slow charging NiCads) takes 14hours. Regenerative breaking efficiency in wheels is known to be poor probably well less than 20% but let us be generous and say 50% and assume the wheel is consuming just 20W just being on. Then 224Wx50% = 112Wx70% = 78.4W less 20W used by wheel.

So if you had the stamina of an athlete and kept it up for a full hour you just might put 58Wh back into the battery. My guess is in reality it might be 1/10th of that if anything at all.

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The voltage might actually not be a problem, if the inductive kick-back is anything to go by:

l4DhHLe.png

 

This was with a 12V 3-phase motor, and I flicked the motor turning with my fingers... easily 50V kickback (although probably very shortlived), with a couple of tries I got it to go over 60V.

EDIT: Got a bit clearer image after fiddling with the scope settings... the scope's crap, and I had to put it together myself (that's why the display is slightly angled :D), but on the other hand, it cost 16€ and it's better than nothing ;) 

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13 minutes ago, Cranium said:

Great looking display on your little scope @esaj!

Yeah, it's not that bad for the price... First time I had to solder surface-mount components, all the resistors and the regulator went well, but I burned one TL084-opamp, luckily it was the piece that was originally missing from the kit, so I had ordered 10 of those :P  Apparently you can't scroll the view up and down, so if the signal doesn't fit into it (like in the above image), you're out of luck. Or maybe I just haven't found out yet how it's done. But you can set the triggers way out of view, which was handy catching those large kickbacks.

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