Help / Advice with my Tesla purchase ?

[Rehab1]

11 minutes ago, Hunka Hunka Burning Love said:

So 2 out of 100 Teslas sold have some control board issues? 

I have not rode myTesla very often because I’m probably one of the 2%. We already know who the other percent is. 

[Rehab1]

5 minutes ago, Marty Backe said:

My God Man! That poor wheel  62-psi on a Gotway tire is like running on a tire made of steel. I run mine at the max listed pressure (45-psi) and that feels plenty firm.

The electronics probably can't handle that kind of vibration 

Those Canadians are always looking for bragging rights. 

[Hunka Hunka Burning Love]

7 minutes ago, Marty Backe said:

My God Man! That poor wheel  62-psi on a Gotway tire is like running on a tire made of steel. I run mine at the max listed pressure (45-psi) and that feels plenty firm.

The electronics probably can't handle that kind of vibration 

What can I say?  I like a firm wheel.    At that pressure the wheel rides smooth as butter though!    The responsiveness is killer at 62 psi.  I used to run 55 psi in my Ninebot One E+ (and I think @SuperSport used to as well), and it just makes the wheel quite nice to ride except for the bumps if you go over rough spots.  Hitting sharp bumps does take its toll though.    I did go offroading, and I'm pretty sure my speeds were over 22 kph on rough bumpy dirt paths so I think the gyro is okay with it even at 62 psi.  The tire is rock hard, but it feels so solid while you ride.  Going back to a lower pressure is difficult...

[Marty Backe]

3 minutes ago, Hunka Hunka Burning Love said:

What can I say?  I like a firm wheel.    At that pressure the wheel rides smooth as butter though!    The responsiveness is killer at 62 psi.  I used to run 55 psi in my Ninebot One E+ (and I think @SuperSport used to as well), and it just makes the wheel quite nice to ride except for the bumps if you go over rough spots.  Hitting sharp bumps does take its toll though.    I did go offroading, and I'm pretty sure my speeds were over 22 kph on rough bumpy dirt paths so I think the gyro is okay with it even at 62 psi.  The tire is rock hard, but it feels so solid while you ride.  Going back to a lower pressure is difficult...

You're not the only one. A local rider likes his in the 60's and whenever I've jumped on one of his wheels, it's way to squirrely for me. Whatever you're used to though.

Because I can, I'm going to blame your little Tesla mishap on extreme tire pressure. Case closed 

[Meng Yang]

I've used my Tesla for over a year. No issues. While I do not have the confidence to accelerate as hard as I want (for fear of cutout), I brake as hard as I want at lower speeds (at higher speeds, I brake more gently, fearing power demand may spike more than the motor can handle). Come to think of it, I should be able to accelerate as hard as I can since I'm able to brake as hard as I can without problem ... well, guess its a confidence thing. My top speed was 53 kph, and whenever I travel, I always cruise along at the Final Alarm i.e. + - 3 kph to 48 kph at higher battery levels. So far so good. My max. usable tire pressure is 40 psi.

 

I've used my V8 for over 2 years now. No issues. With less power, I don't accelerate and brake as hard as I can. I moderate my effort with the speed the wheel is going at. InMotion has an alarm + tiltback system that tells me when I have should taper my effort. I always travel at the top speed of 30 kph. My max. usable tire pressure is 50 psi.

 

I've used my Imitation China-made Airwheel X3 for nearly 3 years now. No issues. However, there was a memorable cutout, though it was rider's fault - with ~10% battery left, I did a series of hard pendulums before braking hard (& it cutout!). As this was my "learning wheel", this kind of mistake was to be expected. From using this wheel, I learn how to ride as hard as possible within the power limitations of each wheel at various battery levels.

[SlowDownDude]

Hey @Meng Yang have you ridden your Tesla through the rain and through puddles etc?  It's raining heavily where I live, should I stop until the weather gets better or can the Tesla handle it?

[Mono]

22 hours ago, Meng Yang said:

Come to think of it, I should be able to accelerate as hard as I can since I'm able to brake as hard as I can without problem

Certainly not. The faster the speed the less strong a wheel can accelerate up to a point where it cannot accelerate at all (if it allows to go up to this speed). If you lean in at this point you will just fall over. This is not true at all for braking power, which is available at all speeds, kind-of good news.

[Marty Backe]

4 hours ago, SlowDownDude said:

Hey @Meng Yang have you ridden your Tesla through the rain and through puddles etc?  It's raining heavily where I live, should I stop until the weather gets better or can the Tesla handle it?

 

[Meng Yang]

9 hours ago, SlowDownDude said:

Hey @Meng Yang have you ridden your Tesla through the rain and through puddles etc?  It's raining heavily where I live, should I stop until the weather gets better or can the Tesla handle it?

Guess Marty has already answered this question. 

As for me, I don't usually ride around in the wet. However, there were occasions where I rode through drizzles and puddles of water for about 5 km. No problem. 

[Meng Yang]

8 hours ago, Mono said:

Certainly not. The faster the speed the less strong a wheel can accelerate up to a point where it cannot accelerate at all (if it allows to go up to this speed). If you lean in at this point you will just fall over. This is not true at all for braking power, which is available at all speeds, kind-of good news.

Why not? 

While I understand we can accelerate harder at low speeds compared to high speeds, I don't understand why we can brake as hard as we want be it low or high speeds. Care to explain? 

[Chriull]

On 11/27/2018 at 8:36 AM, Meng Yang said:

Why not? 

While I understand we can accelerate harder at low speeds compared to high speeds, I don't understand why we can brake as hard as we want be it low or high speeds. Care to explain? 

For accelerating one is bound by the "max torque over speed" limit (https://forum.electricunicycle.org/topic/11477-what-speed-is-safe-to-ride/?do=findComment&comment=201203) .

For breaking the different braking techniques have to be distinguished:

(Regenerative) braking works totally different: The 3 Halfbridges work as step up converter to get the voltage generated by the motor a little above the battery voltage, so that there is a current flowing out of the motor into the battery generating the braking torque. Afair this is more or less done by feeding a PWM signal to the Mosfets at the lower side of the Halfbridges and by adjusting the PWM frequency the voltage is regulated. Imo the body diodes of the upper mosfets are used to rectify the generated motor voltage and feed the current into the battery.

But real details are afair not known/established - at least not around here. Can't remember a in-deep discussion with results about this topic. So motor speed limits/ranges for which this principle works and with which efficiences are not testet/discussed/known. It's just to say that here is no such thing comparable to this "max torque over speed" limit as for acceleration - but maybe some other limiting principles.

Next one would be to break by shortening (putting some fixed load at ) the motor coils - the motor current here should be higher for higher speeds and by this the braking torque.

The third technique to break works by changing the commutation sequence of the coils, so they are not accelerated like with normal driving but decelerated. For this technique there could be a torque over speed diagramm with the "max torque over speed" limit mirrored to the quadrant with negative speeds/torques?

As far as we guess the main braking technique used for EUCs is regenerative braking. One strong clue for this is that the firmwares allows no braking anymore once the battery is full. There were already some discussions about this topics and some other braking techniques could be possible sometimes, but that's only presumptions.

Edit: See https://forum.electricunicycle.org/topic/11839-help-advice-with-my-tesla-purchase/?do=findComment&comment=202607 instead

But from all the papers/web sites/discussions i have read the main "problem" of electric braking is that there is not enough torque at low speeds to come to an "acceptable" standstill - for this additional mechanical brakes are (would be) needed. "Somehow" braking torque dimishes once one approaches a speed of zero. (My naive explanation for this - low "turning" energy - low voltage -> low current -> low torque  )tead.

Edit: dynamic braking (shortening the motor coils) supplies braking force at zero speed. Additionally by the self balancing feature of the EUC and the rider wanting to stop this is no problem in our case.

 

[Meng Yang]

12 hours ago, Mono said:

Certainly not. The faster the speed the less strong a wheel can accelerate up to a point where it cannot accelerate at all (if it allows to go up to this speed). If you lean in at this point you will just fall over. This is not true at all for braking power, which is available at all speeds, kind-of good news.

Another question:

Am I to understand that you meant that the FULL Braking Power is available Regardless of Speed? That means I can brake as hard at 5 km/h or 50 km/h?

Yet another question:

At 10% battery level, why did my Airwheel X3 suffer a cutoff, even though I braked less heavily than normal? Does it mean I can't brake as hard at lower battery level compared to higher battery levels? I don't understand coz you mentioned braking power is available at all speeds (& speeds and battery levels are correlated).

[Chriull]

1 hour ago, Meng Yang said:

At 10% battery level, why did my Airwheel X3 suffer a cutoff, even though I braked less heavily than normal?

The Airwheel X3 is of the first generations of wheels. There were many problems, like BMS cutting off.

"Inbetween generations" used to blow up the mosfets while harder braking.

These wheels behaviour/abilities cannot be compared to nowadays wheels.

[Mono]

4 hours ago, Chriull said:

As far as we guess the main braking technique used for EUCs is regenerative braking.

Just FTR, that's not my conclusion from the evidence I have seen from several independent sources (as already discussed in another thread).

Regen braking should also mean that at low speed acceleration is stronger than braking, because allowed discharge currents are larger than charge currents. But that's not the reason why I came to the above conclusion.

[Mono]

1 hour ago, Meng Yang said:

Am I to understand that you meant that the FULL Braking Power is available Regardless of Speed? That means I can brake as hard at 5 km/h or 50 km/h?

I don't know. For one, if the controller gives no electrical input to the motor at all, we see deceleration. Then, with no input, we see (much) more deceleration at 50km/h than at 5km/h already just because of wind resistance. Then, regenerative braking is somewhat feeding off the back EMF, which diminishes to zero with decreasing speed. That is, there should be the less regen braking power the lower speed, but I think it would be better to look at the equations before to make assertive claims on this one.

[Chriull]

1 hour ago, Mono said:

Just FTR, that's not my conclusion from the evidence I have seen from several independent sources (as already discussed in another thread).

Whellog logs show in most cases regenerative breaking (negative currents). Afair i delivered once a log which could would strenghten assumptions that other techniques are used too? But Whellog data is unfortionately quite inprecise...

1 hour ago, Mono said:

Regen braking should also mean that at low speed acceleration is stronger than braking, because allowed discharge currents are larger than charge currents. But that's not the reason why I came to the above conclusion.

Low speed braking is exactly one of the uncertainties - we'd need some measurements/tests to come from guessing/assumptions to knowledge.

Imo also while balancing, where small decelerations (=braking) is needed this could maybe done much easier and finer by changing the commuting of the coils than switching to regenerative breaking?

I just know, that i am not knowing it and that i have (had? - these discussions were already some time in the past) some personal assumptions...

[Mono]

2 minutes ago, Chriull said:

Whellog logs show in most cases regenerative breaking (negative currents). 

Are these battery currents or motor currents?

[Chriull]

2 hours ago, Mono said:

Regen braking should also mean that at low speed acceleration is stronger than braking, because allowed discharge currents are larger than charge currents. But that's not the reason why I came to the above conclusion.

Just for the records - in case of discharge (acceleration) the voltage from the batteries is "stepped down" to the motor voltage (and vice versa the battery current increased to the motor current), for regenerative braking the motor voltage is "stepped up" above battery voltage (and by this the motor current reduced to a lower battery current)

 

2 minutes ago, Mono said:

Are these battery currents or motor currents?

Good question! That's from my KS16S (which was my first wheel which reported negative currents) and i am strongly assuming it's the motor current. But i did not study the logs and tested  thouroughly enough to give an definitive statement.

The only way to distinguish between regenerative and non regenerative braking in this case is to look at the battery voltage - if it increases by beeing fed with the motor current or not... That was afair how i differentiated this with my KS16B logs, who reported currents unsigned...

2 hours ago, Mono said:

But that's not the reason why I came to the above conclusion.

Btw, what is the reason?

[Mono]

44 minutes ago, Chriull said:

Just for the records - in case of discharge (acceleration) the voltage from the batteries is "stepped down" to the motor voltage (and vice versa the battery current increased to the motor current), for regenerative braking the motor voltage is "stepped up" above battery voltage (and by this the motor current reduced to a lower battery current)

 

Good question! That's from my KS16S (which was my first wheel which reported negative currents) and i am strongly assuming it's the motor current. But i did not study the logs and tested  thouroughly enough to give an definitive statement.

The only way to distinguish between regenerative and non regenerative braking in this case is to look at the battery voltage - if it increases by beeing fed with the motor current or not... That was afair how i differentiated this with my KS16B logs, who reported currents unsigned...

Btw, what is the reason?

The voltage drop between 3m01 and 3m05 in this graph commented by you as "definitely a non regenerative braking" from the Non Regenerative Braking thread was one of them:

and this comment and my own observations/experiments.

 

[RockyTop]

Keep in mind that shorted braking would put out a lot of heat. The energy has to go somewhere.  In my trade (large motors) the heat can heat the room and reqire 10 ton air conditioner or you can regen the power back to the grid and use it to run a 10 ton  air conditioniner.

[Mono]

8 hours ago, Chriull said:

But from all the papers/web sites/discussions i have read the main "problem" of electric braking is that there is not enough torque at low speeds to come to an "acceptable" standstill - for this additional mechanical brakes are (would be) needed. "Somehow" braking torque dimishes once one approaches a speed of zero. (My naive explanation for this - low "turning" energy - low voltage -> low current -> low torque  )

Though that seems not quite true with at least two of my wheels which allow quite strong deceleration right into zero and seamlessly into negative speeds. I can perfectly imagine that electric skateboards and kick scooters have much less sophisticated braking control routines (they don't need these sophisticated controllers because they do not need to self-balance) and that they work only regeneratively.

[Mono]

2 hours ago, RockyTop said:

Keep in mind that shorted braking would put out a lot of heat.

Some time ago I computed the numbers based on the heat capacity of the motor wires and it seemed entirely feasible. It may also well be the case that you can't brake hard for more than a few (tens of) seconds.

[RockyTop]

24 minutes ago, Mono said:

Some time ago I computed the numbers based on the heat capacity of the motor wires and it seemed entirely feasible. It may also well be the case that you can't brake hard for more than a few (tens of) seconds.

The motors that I work with (40hp ) accelerate half the time and brake the other half. Full stop to 1700 RPM  3 - 7 times each minute. So I suspect your are correct about the lesser demand.  

[Chriull]

19 hours ago, Mono said:

The voltage drop between 3m01 and 3m05 in this graph commented by you as "definitely a non regenerative braking" from the Non Regenerative Braking thread was one of them:

Thanks for reminding me!

Quote

and this comment ...

Seems i never got this - was just around my starting time here.

So i change back to my opinon that the wheels use, depending on the situation different braking techniques. From @Daan's citing of Shane Chen this should be regenerative and reverse braking (1). There is a nive overview of the differents braking techniques: https://e2e.ti.com/blogs_/b/motordrivecontrol/archive/2013/10/18/the-art-of-stopping-a-motor#. They suppose to use this reverse braking and change to dynamic braking (shortening the motor coils) approaching zero speed (2)...

Also a nice master thesis "ANALYSIS OF REGENERATIVE BRAKING IN ELECTRIC MACHINES" can be found at https://smartech.gatech.edu/handle/1853/47660. This shows that the maximum reachable braking torque for regenerative braking is linear to speed. For a "surface permanent magnet synchronous machine including core loss resistance" a "little bit below" this - did not get into detailed reading till now (2) to see which applies to our BLDC motors used in the EUCs ... and if he maybe used other settings than we assume that are used with EUCs.

Also http://ieejournal.com/Vol_3_No_2/Different Braking Techniques Employed to a Brushless DC Motor Drive used in Locomotives.pdf shows diminishing torque with decreasing speed for each of the dynamic/regenerative braking techniques (also their "approach" to regenerative braking is to my knowledge different than the one used with EUCs).

So (theoretically!) maximum possible braking deceleration should be (more or less) proportional to speed?! (M=k*v, F=M/r, a = F/m -> a = k*v/(r*m) )

But since with reverse/plugging braking massively high motor currents (==braking torque) can be reached (~2,7 times of normal (acceleration) operation is mentioned in one of these papers) this maximum could be limited by firmware? So the EUC has chances to survive emergency braking? And finaly leaves some more or less constant braking force over speed? 

 

(1) is imo also called plugging braking in many papers. As far as i understand "plugging braking" is (mostly) described as applying full reverse force?

(2) But since an EUC also has balancing "included" this switching to dynamic braking could be superfluous?

(3) Beside nice descriptions of the used models (motor + inverter + power supply) there are some interesting "statements" in there like that the current reachable with regenerative braking is without relation to the specifications of the power supply (battery). So sometimes doing detailed reading could be very interesting to understand such relations.

There is also much theory showing differences between DC motor and different synchrounous machines regarding max torque over speed limits

[Mono]

14 minutes ago, Chriull said:

Also http://ieejournal.com/Vol_3_No_2/Different Braking Techniques Employed to a Brushless DC Motor Drive used in Locomotives.pdf shows diminishing torque with decreasing speed for each of the braking techniques (also their "approach" to regenerative braking is to my knowledge different than the one used with EUCs).

So (theoretically!) maximum possible braking deceleration should be (more or less) proportional to speed?! (M=k*v, F=M/r, a = F/m -> a = k*v/(r*m) )

WIthout having looked into any of this in detail, that doesn't sound as it could possibly be true. It would mean that when switching from forward motion to backward motion one has first decreasing torque when speed approaches zero and at zero speed a torque jump from 0 to maximal torque/acceleration. That would also suggest that there is only minimal torque for backward-self-balancing when going slowly forward. Both neither make sense in my physics intuition (when I activate the motor in forward direction it should have only minor influence whether it is currently slowly moving forward or backward) nor (much more importantly) is it supported by the evidence when riding EUCs.