MSX 100v VS MSX 84v

[Michael Tucker]

There are many variables that effect performance with EUCs; wind, slope, weight, tires, road condition, battery level, firmware, age of wheel, pedal size, rider experience, motor magnets and windings, and even manufacturer quality control. With range tests, even though the results are reported with simple empirical evidence like kilometers traveled over time, it's still just an estimate because of all the variables of your particular ride.  When measuring something like acceleration, most of us are just basing our "results" as an opinion on how fast something felt. Not very scientific. The best measure of comparative acceleration is @Kuji Rolls video comparing an MSX to a KS18XL in a parking lot with cones and measured distance. Even then because the acceleration is activated by leaning, there is no precise way to isolate and repeat the exact leaning pressure each test run.

[mrelwood]

13 hours ago, eddiemoy said:

might be closer to a ratio of the wheel size to the location of the magnets,

In relation to the wheel diameter, the magnets are further away from the edge of the rim on a 14” wheel than on a 16” wheel. So by that theory the 14” should feel more sluggish than a 16” wheel.

I don’t see how the sluggishness or zippyness could be caused by the distance of the magnets from the rim edge.

Even when talking about the virtual gear ratios, I think one thing has been left out from the consideration. The wheel’s job is to keep the balance and stay upright. If the rider causes an inbalance, the wheel will accelerate to fix the inbalance. If the motor has to work more on a larger wheel, it will do so, and possibly consume more energy. But it will still accelerate exactly as much that is needed to fix the inbalance, wether it’s on the first or third gear.

I’m confident the feeling of zippyness and sluggishness depends on two things: 1) how much input the wheel requires to create a certain amount of inbalance, and 2) how effectively the firmware is programmed to fix the inbalance.

The MSX can accelerate like a rocket, but I just have to lean a lot more for it to do so than on a smaller wheel. So the amount of available power, torque or grip is not the issue.

On the firmware side, the S2 feels a whole lot zippier and more effortless to accelerate than the IPS Zero, both with a 14x2.125” tire. Again, not talking about max acceleration, the difference is clear on a mild acceleration as well.

[EUCGUY]

On 5/2/2019 at 10:05 PM, Marty Backe said:

You owe it to yourself to get a set of MSX Powerpads from @EUC GUY. They are a game changer for climbing. I've reviewed them on my YouTube channel. Highly recommended.

P.s. I have no affiliation with Mathias and purchased the ones I use on my MSuper V3s+ and MSX.

Thank you, btw, for those interested, im making a final batch this weekend and next week, last to be sold in a good while as i switch over to monster powerpads. 
 

[stephen]

18 minutes ago, EUC GUY said:

Thank you, btw, for those interested, im making a final batch this weekend and next week, last to be sold in a good while as i switch over to monster powerpads. 
 

Will the monster powerpads fit the msx ,, they look good , 😊

[EUCGUY]

3 minutes ago, stephen said:

Will the monster powerpads fit the msx ,, they look good , 😊

nah  its too big, but those i start selling will be ready for the electronics that comes later.  final stages now to make sure theres no problems to consider, worked fine for me tho, but a few things i like to fix first

[eddiemoy]

7 hours ago, mrelwood said:

In relation to the wheel diameter, the magnets are further away from the edge of the rim on a 14” wheel than on a 16” wheel. So by that theory the 14” should feel more sluggish than a 16” wheel.

I don’t see how the sluggishness or zippyness could be caused by the distance of the magnets from the rim edge.

Even when talking about the virtual gear ratios, I think one thing has been left out from the consideration. The wheel’s job is to keep the balance and stay upright. If the rider causes an inbalance, the wheel will accelerate to fix the inbalance. If the motor has to work more on a larger wheel, it will do so, and possibly consume more energy. But it will still accelerate exactly as much that is needed to fix the inbalance, wether it’s on the first or third gear.

I’m confident the feeling of zippyness and sluggishness depends on two things: 1) how much input the wheel requires to create a certain amount of inbalance, and 2) how effectively the firmware is programmed to fix the inbalance.

The MSX can accelerate like a rocket, but I just have to lean a lot more for it to do so than on a smaller wheel. So the amount of available power, torque or grip is not the issue.

On the firmware side, the S2 feels a whole lot zippier and more effortless to accelerate than the IPS Zero, both with a 14x2.125” tire. Again, not talking about max acceleration, the difference is clear on a mild acceleration as well.

When trying to figure out how things work, you may want to try a more controlled comparison.  Like I mentioned and you should know by now that the 16” and the 18” wheels share the same motor where as the 14” is not.  So makes sense to compare the same motor, keeping at least that constant.  

‘The motor being the same kind of the same as you on a manual unicycle and trying different wheel sizes but keeping the same crank arm lengths.  EUC motor is - to you and the same crank arms on manual unicycle.   I don’t know how it can be any clearer.  The force you are applying from your muscles are the same.  You haven’t gotten stronger or weaker.  Get on the manual unicycle and try if you cannot visualize the difference.   If you don’t understand manual unicycles, most people don’t   The other example would be multi speed bike.  Try a lower gear and turn the pedal, should be easy.  Try a higher gear, should be much more difficult   That is similar.

‘You will find that if you keep the same crank arm length and change the wheel size, it is much harder to ride a bigger unicycle.  The acceleration would be shit.  But the top speed is faster.  The same holds true with 16 vs 18.  These motors have the same revolutions per given voltage.  Same torque.  But now the torque is applied at different location just like the manual unicycle example. With bigger wheel and revolutions per volt, we get the behavior we have been feeling.  Sluggish on the 18” but faster top speed.  Quicker to accelerate and decelerate on the 16’ but lower top speed.   Because these motors have a given revolution per voltage and are the same.  But the 18” goes further per revolution, it is bigger.  

‘It all makes sense to me.  And it fits into my thesis and what I experience. This is as clear as I can make it.  I hope this helps. 

Edited May 4, 2019 by eddiemoy

[eddiemoy]

@mrelwood, here is a picture to help illustrate.   These are 20” and 24” unicycles side by side with the same length crank arms.  

Notice the position of the pedals.  That is same as the location of the mage nets on EUC.  Which one is easier to pedal?  Which one goes faster as in top speed?  This is a clean comparison.  2hen you start changing things like putting bigger tires on the 20”, then it starts to become less clear.  Though if you put bigger tires on the 20”, then you can imagine that the wheel get bigger, so behavior would be closer to the 24”. I’m sure the tire mass has some effect, but I’m not sure how much. 

[stephen]

29 minutes ago, EUC GUY said:

nah  its too big, but those i start selling will be ready for the electronics that comes later.  final stages now to make sure theres no problems to consider, worked fine for me tho, but a few things i like to fix first

They look good mate you do a good job

[mrelwood]

2 hours ago, eddiemoy said:

When trying to figure out how things work, you may want to try a more controlled comparison.  Like I mentioned and you should know by now that the 16” and the 18” wheels share the same motor where as the 14” is not.  So makes sense to compare the same motor, keeping at least that constant.  

I understand very well the reason why gears and crank lengths affect the required force for a certain amount of acceleration. That’s not the problem.

Problem is that you are indeed doing a controlled comparison of a limited set of variables in a separated frozen timeframe, and you extrapolate the result to cover the whole interactive moving system with all the other variables added back in.

Overly simplified example: A certain race car with a smaller rear wing always wins. Hence, smaller rear wing is better in a race car, because it offers less wind resistance. It might have that effect, yes, but it’s not the reason for winning.

The physics of a simple EUC are not very simple when considering all affecting variables. And since nobody has measured the sluggishness/zippyness, the variable we are discussing is based solely on human perception, which is also largely affected by psychology. So you see why a controlled comparison of one measure can’t really work in this case?

A 14” wheel generally feels snappier than a 16” wheel. Considering your experience with various wheels I’m pretty sure you agree with that. Yet it contradicts your theory of the relative magnet location being the reason for zippyness/sluggishness.

Another point: Any EUC with a low tire pressure feels more sluggish than the same exact wheel with a high tire pressure. As the variable very noticeably affects sluggishness, it can’t be disregarded when looking for the reason for sluggishness.

One issue is ofcourse the term itself, as different people probably mean different things by sluggishness/zippyness. All in all, an actual scientific pondering of the matter hasn’t been approached very much, in this or any thread.

[eddiemoy]

49 minutes ago, mrelwood said:

I understand very well the reason why gears and crank lengths affect the required force for a certain amount of acceleration. That’s not the problem.

Problem is that you are indeed doing a controlled comparison of a limited set of variables in a separated frozen timeframe, and you extrapolate the result to cover the whole interactive moving system with all the other variables added back in.

Overly simplified example: A certain race car with a smaller rear wing always wins. Hence, smaller rear wing is better in a race car, because it offers less wind resistance. It might have that effect, yes, but it’s not the reason for winning.

The physics of a simple EUC are not very simple when considering all affecting variables. And since nobody has measured the sluggishness/zippyness, the variable we are discussing is based solely on human perception, which is also largely affected by psychology. So you see why a controlled comparison of one measure can’t really work in this case?

A 14” wheel generally feels snappier than a 16” wheel. Considering your experience with various wheels I’m pretty sure you agree with that. Yet it contradicts your theory of the relative magnet location being the reason for zippyness/sluggishness.

Another point: Any EUC with a low tire pressure feels more sluggish than the same exact wheel with a high tire pressure. As the variable very noticeably affects sluggishness, it can’t be disregarded when looking for the reason for sluggishness.

One issue is ofcourse the term itself, as different people probably mean different things by sluggishness/zippyness. All in all, an actual scientific pondering of the matter hasn’t been approached very much, in this or any thread.

I don't doubt there are many factors affecting the feel of the wheels.  

I can't give you the complicated calculations that describe what is happening and if I did you would understand it anyway.  So simplifying it is for the masses.  We use examples that people can relate with.  It is obvious it doesn't relate with you.  I'm not going to sit here and split hairs with you.

You can lower the tire pressure on a 16" wheel to have the same contact patch and it will still feel more zippy than an 18" wheel.  I don't think the contact patch is a big factor.  Size of the wheel is a probably a bigger factor.

Anyone who has ridden different wheels can feel the difference between the 14, 16, 18 wheels and we all describe it as sluggish/zippy.  Don't think our experiences are all that different.  

 

[Issah]

On 5/4/2019 at 1:26 PM, EUC GUY said:

Thank you, btw, for those interested, im making a final batch this weekend and next week, last to be sold in a good while as i switch over to monster powerpads. 
 

Oh jeez. I need those pads, but can't afford to buy them before May 20th. Crossing my fingers you won't run out of stock before then.

[stephen]

On 5/4/2019 at 12:26 PM, EUC GUY said:

Thank you, btw, for those interested, im making a final batch this weekend and next week, last to be sold in a good while as i switch over to monster powerpads. 
 

@EUC GUY i have your pads the first batch now i see they have an outer ring pla plastic can this be added to my old pair as it looks nice .. My pads  are still in perfect condition not even worn to say I've done over 2000 miles and i few falls here and there😊😊 thx

Edited May 5, 2019 by stephen

[EUCGUY]

29 minutes ago, stephen said:

@EUC GUY i have your pads the first batch now i see they have an outer ring pla plastic can this be added to my old pair as it looks nice .. My pads  are still in perfect condition not even worn to say I've done over 2000 miles and i few falls here and there😊😊 thx

The shape would fit, but I changed the height of the ramped part by a few mm after first gen, installing the ring would not allow for enough foam to stick up and instead the ring would be felt in the legs. 

[stephen]

1 hour ago, EUC GUY said:

The shape would fit, but I changed the height of the ramped part by a few mm after first gen, installing the ring would not allow for enough foam to stick up and instead the ring would be felt in the legs. 

☹️

Edited May 5, 2019 by stephen

[RayBanMonster]

On 4/25/2019 at 1:01 PM, meepmeepmayer said:

That absolutely correct.

But the 84V 1300Wh/1600Wh battery is 6p, while the 100V 1240Wh battery is 4p, so the 84V has 50% higher peak current.

So the theoretical peak power of the 84V MSX is 84*6/100*4 = 126% that of the 100V MSX. It's bigger.

You'll never reach those crazy high theoretical peak numbers with either wheel, so it doesn't matter. Get the wheel you like. The 100V MSX is faster and you can enjoy the prestige, the 84V MSX gives you better range, otherwise it's more or less the same wheel. The Z10 looks great and you won't overlean it also.

All three wheels are safe (as well as all the other current brand wheel with big enough batteries). On paper, the 84V 6p 18 inchers like the MSX 84V or KS18XL beat other 18 inchers in peak power.

Thanks for this informative modifier.. your "Kung Fui"is strong... I didn't factor the issues you  raised, thanks

[Elliott Reitz]

The only part number for the wheel-assembly I"e seen on any MSX (in adv pics) is:

60V-180900297

As for torque being current limited by the batteries - I doubt that theory since the "series resistance" to deliver 40+ Amps exceeds the rating of the 12Ga wires in the rest of the motor system.   If so it would only be noticible at a nearly dead stop to climb a curb or very steep slope for less than 3 seconds (more would fry the wires togeather or burn one like a fuse). 

Disclaimer:  I have an MSEE plus 30 years experience in engineering.

[Elliott Reitz]

Additionally, I found the internal resistance of the battery cells is 0.04 ohms.  Link: https://www.hurt.com.pl/prods/bat/_li_ion/ncr18650ga.pdf

So, assuming 24 cells in series for 100V, the internal resistance of the 100V series is 0.96 ohms. This means a 10A strand drops nearly 10V at that surge of current.  It also means 15A will drop 14.4V. 

So going back to the 4x24 vs 6x 20 cells wiring, the 100V system would already be running 60A to get to 85V... and by the time the 84V were drawing 60 amps it would be dropping 8 volts (100 V still has more power at 84V system).    Both systems have a theoretical 100A maximum battery limit through series resistance. 

100V has more power and more torque.

QED

[Electroman]

4 hours ago, Elliott Reitz said:

The only part number for the wheel-assembly I"e seen on any MSX (in adv pics) is:

60V-180900297

As for torque being current limited by the batteries - I doubt that theory since the "series resistance" to deliver 40+ Amps exceeds the rating of the 12Ga wires in the rest of the motor system.   If so it would only be noticible at a nearly dead stop to climb a curb or very steep slope for less than 3 seconds (more would fry the wires togeather or burn one like a fuse). 

Disclaimer:  I have an MSEE plus 30 years experience in engineering.

Thanks for the info.

I run my 1600Wh MSX as 20s9p + lower gauge from harness to the board itself, power is the same from what I can feel, only I can go a bit longer of course.

Seen what the battery can do even to pliers, stupid mistake but enough about that, in fact Fronius are building portable stick welders with much smaller li ion packs.

Limitation must be elsewhere indeed.

[esaj]

46 minutes ago, Elliott Reitz said:

Additionally, I found the internal resistance of the battery cells is 0.04 ohms.  Link: https://www.hurt.com.pl/prods/bat/_li_ion/ncr18650ga.pdf

So, assuming 24 cells in series for 100V, the internal resistance of the 100V series is 0.96 ohms. This means a 10A strand drops nearly 10V at that surge of current.  It also means 15A will drop 14.4V. 

So going back to the 4x24 vs 6x 20 cells wiring, the 100V system would already be running 60A to get to 85V... and by the time the 84V were drawing 60 amps it would be dropping 8 volts (100 V still has more power at 84V system).    Both systems have a theoretical 100A maximum battery limit through series resistance. 

100V has more power and more torque.

QED

Was going to write about the same thing, but you got it first...  Yeah, the 24S packs will have higher internal resistance, couple that with less packs in parallel, it might be that the 100V versions actually have lower maximum (safe operating range) power output vs. 20S, and the only upside is (up to a point) higher top speed. But there are a lot of variables at play, so it might well be that the the internal resistance of the battery packs is not the main issue.

[Chriull]

Some (technical) thoughts regarding MSX 84V (20s6p battery configuration) vs MSX 100V (24s4p battery configuration):

Assumptions:

- both wheels have the same motor

- one Li Ion Cell has an internal resistance of 0,04 Ohm

- the motor coils (2 of them in series, as they are commuted each time) have 0.3 0.2 Ohm ohmic resistance (this number is very wildely guessed - could be anywhere else in very about this range. This is just assumed to have some numbers to work with!)

- 60 km/h no load speed for 84V -> leading to a kv of 0,714 km/h/V Edit: (1)

- ~78 km/h no load speed for 84V -> leading to a kv of 0,93 km/h/V

- contact/wiring and mosfet resistances are not considered

- there is a current limit at 120A (from an old post of an gotway representative)

Internal resitance of the 20s6p battery: 20 * 0,04 Ohm / 6 = 0,133 Ohm

Internal resitance of the 24s4p battery: 24 * 0,04 Ohm / 4 = 0,24 Ohm

 

The maximum torque over speed diagram (operational limits of the motor) are then defined by the maximum no load speeds on the x-axis:

84V * 0,93 km/h/V = 78.5 km/h

100.8V * 0,93 km/h/V = 94.2 km/h

On the y-axis (current == torque) the limit is set by the internal resistances and the Voltage (I = U/R) - the "no speed" (short-circuit) current flowing:

84V, 20s6p: I = 84V/(0,24+0,2)Ohm = 252 A

100V, 24s4p: I = 100V/(0.133+0.2)Ohm = 229A

So with the abovementioned assumptions the 100V version has more torque and speed in any case. (But this could change with different values for motor coil resistance and current limit, which are just guessed)

But, there could exist a point in time, were the 84V Version "overtakes" the 100V version torque wise by having a higher battery capacity (slower voltage decrease) ... if one drives long enough ... But although could not be - did not look at this in detail...

Edit:

Unfortionately i took the numbers for no load speed from the wrong row and got the Z10 numbers instead of the MSX 84 numbers ;(

The MSX 84 has about 78 km/h at 84V! ... not 60 km/h!...

So i changed all the number above and the charts accordingly.

I also took now 0.2 Ohm for the two motor coils in series instead of the 0.3 Ohm (this value was still afair from an "old" m3s - with the higher power ratings this could/should decrease a bit the coil resistances? Or not - have no idea )

 

Edited July 21, 2019 by Chriull
numbers reworked

[meepmeepmayer]

The 84V has more torque though, going by real world reports Or at least it has more oomph/instant acceleration, maybe that's mathematically different from torque.

Keep in mind that what the battery can do is not necessarily the real-life limitation, but mostly a theoretical one. Normal riding is like 10-15A which is far away from 40 or 60 or wherever 4p vs. 6p would make a difference.

A 800Wh (3p) MSX would not feel different than the 1600Wh MSX, the firmware is the same after all. And the firmware determines how much power a wheel is allowed to draw until you run into the actual hardware limits at high speeds (which looks like it would be the motor or the shitty cabling). See the Nikola with its higher battery usage to get more oomph/torque, it's a firmware choice anywhere but at the hardware limits.

So I assume (without further knowledge) the higher torque of the 84V is due to the firmware (and if it's only the exact same firmware resulting in higher torque for high current/low voltage vs. low current/high voltage).

Would love to hear more info and speculation about this (torque) topic. I wish there was a EUC technical whitepaper of some kind.

[Elliott Reitz]

23 minutes ago, meepmeepmayer said:

The 84V has more torque though, going by real world reports Or at least it has more oomph/instant acceleration, maybe that's mathematically different from torque.

Keep in mind that what the battery can do is not necessarily the real-life limitation, but mostly a theoretical one. Normal riding is like 10-15A which is far away from 40 or 60 or wherever 4p vs. 6p would make a difference.

A 800Wh (3p) MSX would not feel different than the 1600Wh MSX, the firmware is the same after all. And the firmware determines how much power a wheel is allowed to draw until you run into the actual hardware limits at high speeds (which looks like it would be the motor or the shitty cabling). See the Nikola with its higher battery usage to get more oomph/torque, it's a firmware choice anywhere but at the hardware limits.

So I assume (without further knowledge) the higher torque of the 84V is due to the firmware (and if it's only the exact same firmware resulting in higher torque for high current/low voltage vs. low current/high voltage).

Would love to hear more info and speculation about this (torque) topic. I wish there was a EUC technical whitepaper of some kind.

So let's consider the battery pack series resistance more carefully, and then a more extreme example the battery pack difference. 

At 0.04 ohm/battery, the battery resistance of the 100V battery pack is (24*0.04/4) = 0.24 ohms, and the 84V pack  (20*.04)/6 = 0.133. 

At 200Amps motor consumption,

    ---- the .24 ohms would reduce 100V to 52V, and ...

    ---- the 0.133 ohms would reduce the 84V to 57.4. 

So yes as mentioned above there is a cross-over point... which appears to be pretty close to 200A.   I doubt that small difference is experienced by anyone side-by-side though I've asked on FB where there were 100V & 84V riders riding together (I've not yet seen side-by-side nor anything other than speculation over torque). 

Disclaimer:  yes, I'm actually an engineer. 

Edited July 19, 2019 by Elliott Reitz

[Elliott Reitz]

Via another example motor current (I found the crossover point) ... 150A both batteries are only putting out 64V as shown:

100V - 150A * .24ohm = 64V

84V - 150A * .133ohm = 64V

So that equates to 64V * 150A = 9600W, or 12.8 hp... .  Converting to torque more by exmple I found for ebike where 1000W produced 160nm so guessing that would scale to 1536 nm here 1132 ft-lbs.  I also get 1120 ft-lbs via the 12.8 hp converter with 60 rpm (approx 1 turn/sec on a 1foot wheel) (similar answer without motor specs to work with). 

Reasonableness check?  Well my EBR 1190sx (fast motorcycle) has over 150 ft-lbs, 220hp and its potential to wheelie is why I have an EUC.     1120 ft-lbs is enough to dead lift a 300 lbs person up a stairway if he could ride it. 

[mrelwood]

IIRC the 84V MSX has a low battery tilt-back at 72V, which makes any behaviour below that voltage a moot point.

Edited July 20, 2019 by mrelwood

[Elliott Reitz]

 

On 7/19/2019 at 4:16 PM, Elliott Reitz said:

Via another example motor current (I found the crossover point) ... 150A both batteries are only putting out 64V as shown:

100V - 150A * .24ohm = 64V

84V - 150A * .133ohm = 64V

So that equates to 64V * 150A = 9600W, or 12.8 hp... .  Converting to torque more by exmple I found for ebike where 1000W produced 160nm so guessing that would scale to 1536 nm here 1132 ft-lbs.  I also get 1120 ft-lbs via the 12.8 hp converter with 60 rpm (approx 1 turn/sec on a 1foot wheel) (similar answer without motor specs to work with). 

Reasonableness check?  Well my EBR 1190sx (fast motorcycle) has over 150 ft-lbs, 220hp and its potential to wheelie is why I have an EUC.     1120 ft-lbs is enough to dead lift a 300 lbs person up a stairway if he could ride it. 

 

On 7/20/2019 at 2:38 PM, mrelwood said:

IIRC the 84V MSX has a low battery tilt-back at 72V, which makes any behaviour below that voltage a moot point.

So unless there are different controllers or the controller is smart enough to set a different threshold on the 100V model, this threshold would mean:

.... the 100V MSX ALWAYS has more TORQUE too.   

eg: 

.... (84-72)V / 0.133 ohm = 90 A.  And 90A*72 = 6480 W (power dissipated across the motor)

...  (100-72)V / .24 ohm = 116 A.  And 116A * 72 = 8400 W  (assumes same tiltback voltage)

1.3 times the torque under maximum load minimum speed (with identical threshold controller).

OTHERWISE, if the controller uses an 86 % nominal voltage tilt back it would go the other way.

.... 72.24V * 90 A = 6502 W

... 86 V * (I = (100-86)/.24 = 58.3) = 5017.

So STILL a side-by-side test will be needed to determin dead-lift torque vs configuration.