What’s the point of higher voltage? (Split from “Sherman-S 3600wh: 100V, 20", suspension, 97lb”)

[soulson]

3 hours ago, The Brahan Seer said:

If you have a 2kW motor that is 84V or a 2KW motor that is 134v is the torque and top speed the same (everything else being equal)?

What is the typical efficiency (in %) of  84, 100 and 134V motors?

 

If you have a 2kw (power) motor that is rated at 84v (voltage) and another 2kw motor rated at 134v, with "all other things being equal", the 84v motor will have more torque than the 134v motor.

This counterintuitive result is because the torque output of a PMSM is proportional to the quadrature axis current of the motor's stator windings. If you hold the power constant at 2kw, and power = voltage * current, then when you increase the voltage, the current must decrease.

However, power = torque * angular velocity too. Since the power stayed the same and the torque decreased, the angular velocity must increase. So the 134v 2kw motor will be faster, with "all other things being equal." (Faster in the sense of top speed; it will take longer to reach the top speed on the 134v motor without loss of balance because there is less torque available, so you won't be able to lean as hard.)

Edited March 23, 2023 by soulson

[JeremySPFF]

19 hours ago, mrelwood said:

You keep bringing up the car comparison. The reason why you aren’t getting the answer you want, is that there really isn’t one. Several people are trying to point it out to you, but it send like you don’t believe us.

I understand and disagree with what you and others are saying. Just because it hasn't been done on an EUC yet doesn't mean it can't. All of the points people are bringing up are personal preferences, or complaining about the accuracy of the testing, or are things that can be accounted for. We can easily factor out the things everyone is saying, like tire differences (use the same tire on both), rider differences ( use the same rider, in the same gear), wind differences (use a tunnel or closed track). I do agree that we cant be absolutely sure every watt was used, but that doesn't mean we should throw out that data. I am looking for objective data instead of subjective. If all you need is subjective reviews to make a purchase, that is great, but not me and I'm not sure why everyone is trying to convince me that I shouldn't expect it.

 

18 hours ago, sbb said:

Heck, just air drag differences from people of the same weight, but different heights and safety gear shape. 

If air drag makes the video unusable for you, that is your preference and you can throw those results out. I would much rather have objective and direct comparison videos that are slightly scientifically flawed, than subjective individual reviews.

23 hours ago, techyiam said:

Kuji timed his acceleration tests.

I really liked when he did this, it was exactly what I was looking for, and it helped me make a decision on a wheel. Unfortunately he doesn't post often and I think he dropped the acceleration tests.

 

[JeremySPFF]

3 minutes ago, soulson said:

If you have a 2kw (power) motor that is rated at 84v (voltage) and another 2kw motor rated at 134v, with "all other things being equal", the 84v motor will have more torque than the 134v motor.

This counterintuitive result is because the torque output of a PMSM is proportional to the quadrature axis current of the motor's stator windings. If you hold the power constant at 2kw, and power = voltage * current, then when you increase the voltage, the current must decrease.

However, power = torque * angular velocity too. Since the power stayed the same and the torque decreased, the angular velocity must increase. So the 134v 2kw motor will be faster, with "all other things being equal."

Thank you, this is the easiest to follow technical information I have heard.

[OldFartRides]

Jeremy, maybe you should be that guy. 

[JeremySPFF]

9 minutes ago, OldFartRides said:

Jeremy, maybe you should be that guy.

I have come to the same conclusion. My original question has also been answered in an easy to understand way that explains the technical differences between voltage by soulson.

[chanman]

1 hour ago, soulson said:

f you hold the power constant at 2kw, and power = voltage * current, then when you increase the voltage, the current must decrease.

We aren't actually holding the power constant though, with the new generation of wheels we're generally keeping the current output capability the same while increasing the voltage.

Edited March 23, 2023 by chanman

[soulson]

That is true. But I was answering a specific question about keeping the power "and all other things" equal.

[techyiam]

7 hours ago, JeremySPFF said:

Again, it's relevant to me and that's the point of the post and the data I am looking for. If you don't need it, that's great, but why are you trying to convince me that I don't need it?

On the contrary. 

You are trying to persuade us that data provided by Go George Go and others are useless, irrelevant but 0 to a specific speed times are relevant. 

I am merely providing reasons why your claim is no more relevant, and flawed. There are just way too many factors that can skewed the results.

Each person will decide for himself or herself which data is relevant.

But if you wish to influence others, at least provide a convincing argument, and not a flawed one.

7 hours ago, JeremySPFF said:

most likely a lot of other riders

Purely speculative. 

 

Edited March 23, 2023 by techyiam

[mrelwood]

18 hours ago, The Brahan Seer said:

If you have a 2kW motor that is 84V or a 2KW motor that is 134v is the torque and top speed the same (everything else being equal)?

The problem is that everything else can’t be equal. If you increase the voltage, you either add more cells (more battery capacity, more resistance) or organise them differently (less batteries in parallel, less current). Both affect the wheel’s performance. Like I said before, we know how each single parameter changes things, but you can’t change just one thing, so the end result is challenging to calculate.

 

15 hours ago, JeremySPFF said:

Again, it's relevant to me and most likely a lot of other riders

That is only your subjective view though. Objectively, looking at what people have requested at the forum, Telegram chats etc over the years, I  don’t remember anyone else requesting what you are. And for good reasons, which are already outlined in this thread.

15 hours ago, JeremySPFF said:

why are you trying to convince me that I don't need it?

Because the way you have so far described for the data to be collected is faulty, would probably cause the data to be misleading, and might just as well lead you into making a wrong purchase decision. If you need faulty data to make a purchase decision, nobody’s stopping you. But to think that your purchase decision would then be someone better, is false.

14 hours ago, JeremySPFF said:

I understand and disagree with what you and others are saying.

You are then also disagreeing with facts though.

14 hours ago, JeremySPFF said:

rider differences ( use the same rider, in the same gear),

Sounds like you didn’t read my previous reply. Imagine this: Kuji accelerated the master to 50km/h in 3.5 seconds, and the V13 in 3.0. Some other riders though accelerate faster on the Master. Heck, I would accelerate faster on my V11 than either of those. How can you consider such data to be objective? How do you even take in such data? Omit the ones that you feel to be irrelevant? That would make the data subjective.

14 hours ago, JeremySPFF said:

I am looking for objective data instead of subjective.

Please describe how would you organise an “objective” acceleration test for EUCs?

14 hours ago, JeremySPFF said:

If all you need is subjective reviews to make a purchase, that is great, but not me and I'm not sure why everyone is trying to convince me that I shouldn't expect it.

I’m the most pedantic buyer I know of, and I make a spreadsheet on basically any purchase decision that requires more than a few seconds to decide. Yet it’s clear to me that on self-balancing vehicles any acceleration data can’t be a part of an objective comparison.

If the tests that people have been making for a decade isn’t good enough for you, you need to make the comparisons yourself. Expecting others to match your criteria for objective testing is futile, especially when you are expecting to see objective data that can’t be objectively measured.

14 hours ago, JeremySPFF said:

I really liked when he did this, it was exactly what I was looking for, and it helped me make a decision on a wheel.

I hope you didn’t subjectively rely on one person’s results though.

[The Brahan Seer]

4 hours ago, mrelwood said:

The problem is that everything else can’t be equal.

I didn't phrase my question very well. I was actually meaning that 'the everything else being equal' was the rider weight, riding style, environment, temp etc.

I wanted to know if there was any difference between the power delivery of a motor rated with the same power output but different voltages.

ie if I had a 84V 2kw motor EUC verses a 100v (or 134v) 2kw motor EUC 

I hear the expression:

VOLTAGE is like the pressure that pushes water through the hose. It is measured in volts (V). CURRENT is like the diameter of the hose.

But how does that translate to BLDC motors? with P=IV etc but motors behaving differently with magnetic saturation which is way over my head and makes me realise I have absolutely no idea what any of the figures actually mean anymore. 

But I have come to the same conclusion as you that it is currently impossible to know with the information we currently have.

Do we know anything about the actual performance specs of any of the motors? Even an efficiency graph would help so much.

As mentioned previously above one day we really need to put all these wheels on a dyno, rolling road to get at least some comparison.

I cannot work out from anything posted online about how each wheel behaves compared to others and I don't have access to any to try myself.

So I am still non the wiser other than bigger voltages equates to higher rpm and therefore speed (everything else being equal) and thats it.

 

 

 

[JeremySPFF]

7 hours ago, mrelwood said:

That is only your subjective view though.

Yes, my subjective view is that I look for objective information to make a decision. This is what I am trying to explain. The problem is you don't understand the difference between objective and subjective.

 

7 hours ago, mrelwood said:

How can you consider such data to be objective?

You still don't understand, objective data is measurable. If Kuji runs 5.8, that is one datapoint, when we group all riders data points, we get a collective picture. Objective data isnt always correct but it is ALWAYS MEASURABLE, when viewed with other objective results we get a clearer picture. Subjective is when Kuji says 'this feels fast to me'. I cannot measure how it feels to him.

 

7 hours ago, mrelwood said:

Please describe how would you organise an “objective” acceleration test for EUCs?

I am so glad you asked. Eevee's just posted a video with some good objective information and testing. Not perfect, but a lot better than only subjective information.

 

7 hours ago, mrelwood said:

Yet it’s clear to me that on self-balancing vehicles any acceleration data can’t be a part of an objective comparison.

This is just your opinion. In my opinion, the video above gives me a lot more of what I need. Acceleration tests are what I am looking for. Maneuverability tests are what I am looking for. Stress tests are what I am looking for. Comparison's where both wheels undergo the same tests are what I am looking for. You can argue my preference is wrong, but you cant say the tests aren't objective unless you don't understand what that means.

 

7 hours ago, mrelwood said:

I hope you didn’t subjectively rely on one person’s results though.

You can always tell someone is losing an argument when they try to put the other person down.

[JeremySPFF]

17 hours ago, techyiam said:

You are trying to persuade us that data provided by Go George Go and others are useless

I am not. All I am saying is that it is subjective. Subjectivity is not useless or irrelevant, its just not the same as objective. In general, my argument is that most of the information on EUC's is subjective and we should also add objective data to the results to get a better picture.

[Mono]

On 3/22/2023 at 7:49 PM, soulson said:

Advertised figures that matter on their own:

1. Continuous power output in watts (of the whole system: batteries, controller, and motor)
2. Peak power output in watts IF the amount of time it can be sustained is specified in seconds, again for the whole system
3. Battery capacity in watt*hours
4. Efficiency of the whole system as a dimensionless ratio of watt*hours consumed to watt*hours delivered to pavement

Advertised figures that don't matter on their own:

1. System voltage
2. Peak power output if the amount of time sustained is NOT specified
3. Number of transistors in the controller
4. Current rating of xyz component
5. Motor power rating
6. Free spin speed

These figures can be useful, but only if you know other details about the wheel/rider/riding conditions.

Yes, I only don't understand why free spin speed is not useful. We know that up to 1/2 free spin speed the motor power increases with speed and above 1/2 free spin speed the power decreases with increasing speed while the power requirements increase which dramatically increases the risk of an overlean. I find hence free spin speed to be valuable information on it's own right. Sure, when battery or controller generate only 100W for a 3000W motor, this is irrelevant. But that's not likely to be the case. The limits of battery or controller should generally be relevant close to zero speed (where current is maximal) and not at 1/2 free spin speed, am I wrong?

Edited March 24, 2023 by Mono

[OldFartRides]

“ The problem is you don’t understand the difference between objective and subjective “.

”Eevee’s just posted a video  with some good objective information and testing”.

Well, on your rec. I suffered through twenty seven minutes of mostly bromance theatre with a sprinkling of objective testing and some contradictory misinformation.

From the vid. : 

6:20 - “4000 watt motor…Never been an euc with this motor in it- with this much power before either. Even crushes the v13 in terms of power - mostly because the controller can deliver more power to the motor. I actually think the v13 is more powerful”.

19:08 - “ this 4500 watt motor”

Maybe you were impressed with the lab coats and  clipboards ?

You make the objective/ scientific content Jeremy. Wow us all.

[JeremySPFF]

1 minute ago, OldFartRides said:

Well, on your rec. I suffered through twenty seven minutes of mostly bromance theatre with a sprinkling of objective testing and some contradictory misinformation.

So, your problem is that the video is bad and you don't like the actors? But you do agree some of the testing was objective?

1 hour ago, JeremySPFF said:

Not perfect, but a lot better than only subjective information.

As you can see, I already said it wasn't perfect. It is however an example of objective information. Before you put more words in my mouth, the video also has subjective information.

 

2 minutes ago, OldFartRides said:

You make the objective/ scientific content Jeremy. Wow us all.

Again, personal attacks are a clear sign you have no real ammo in an discussion.

 

I get it, you guys dont really want me around. I'll see myself out.

[OldFartRides]

Wasn’t an attack son, it’s a challenge. You don’t like what you see on the boob tube ? Do better. No one is trying to run you off. 
 

[MetricUSA]

Forget about preformance, the true reason of higher voltage is simple, the less current for the same amount of power, the smaller gage wire you need to use, and the lighter motor and the less heat generated... But you don't notice any of that because every new model made has a bigger more powerful motor in it... 

With that said, no one needs to make a bigger motor at all, they are big enough now, absolutely no need for a brand new motor... 

[techyiam]

2 hours ago, JeremySPFF said:

20 hours ago, techyiam said:

You are trying to persuade us that data provided by Go George Go and others are useless

I am not. All I am saying is that it is subjective. Subjectivity is not useless or irrelevant, its just not the same as objective. In general, my argument is that most of the information on EUC's is subjective and we should also add objective data to the results to get a better picture.

Let's see what @JeremySPFF has to say about that, some posts earlier. 

 

On 3/22/2023 at 6:46 AM, GoGeorgeGo said:

its not a feeling, its empirical data points of me overtorquing the wheel to cutout. you can watch how pathetic it is in my god mod review video where i over torque the wheel about 9 times on the incline test.

i have also over stepped the torque limits several times riding it normally

 

On 3/22/2023 at 7:33 AM, JeremySPFF said:

I'm saying, in fact, that empirical data is useless.

[soulson]

11 hours ago, Mono said:

...We know that up to 1/2 free spin speed the motor power increases with speed and above 1/2 free spin speed the power decreases with increasing speed while the power requirements increase which dramatically increases the risk of an overlean...

I don't think we do know that, though. If we did know that, then maybe I could see saying that free spin speed is a useful metric, but as far as I know, no manufacturer advertises the point on the power/torque curve for their motor where field weakening is employed to increase angular velocity (at the cost of torque). A lot of PMSM power curves will show this behavior, but it's still a decision by the engineer whether to employ it or not. It is not an inherent characteristic of PMSMs, and it comes with a significant tradeoff as you mention further in your post.

[Chriull]

2 hours ago, soulson said:

but as far as I know, no manufacturer advertises the point on the power/torque curve for their motor where field weakening is employed to increase angular velocity (at the cost of torque). A lot of

Seems as Begode employed this by it's high speed mode, which as to be activated with the app. They advertise now two free spin speeds.

"Older" wheels like the ks18xl and others from this time do (did) not implement field weakening. Different overlean and lift cut off logs suggest an about linear current vs speed limit.

... Which of course could change with every firmware update ... Which should create some attention with some new introduced settings and notable different behaviour.

[Poker]

One thing I didn't see mentioned in this thread (I might have missed it) is that if you got a 100V wheel and a 134V wheel with the same W/H you should be able to charge the 100V wheel faster. 

In reality there may be other limiting factors tho, like charging ports being the bottleneck for how much current you can charge with.

 

 

Edited March 25, 2023 by Poker

[superox]

You should be able to charge the 134V wheel faster, as it takes less amps to move the same amount of energy, and their batteries have fewer amp-hours to charge. So if the bottleneck is 10A limit on the charge port, you can move more energy through it when using a higher voltage.

In practice the chargers are the same, and only tuned to give more volts/less amps, so at the end of the day they provide the same amount of watts.

[Poker]

Well no, more cells in parallels means less current going through each series of cells and that means you can have a higher charging current without risking damage to the cells as that is the limiting factor.

Edit: I thought about it a bit more and honestly I could be wrong here, the need for less current at higher voltage could be better, would have to do some math to be sure.

Edited March 25, 2023 by Poker

[mrelwood]

 

On 3/24/2023 at 1:37 PM, The Brahan Seer said:

VOLTAGE is like the pressure that pushes water through the hose. It is measured in volts (V). CURRENT is like the diameter of the hose.

I was taught the other way around, voltage being the potential (large hose diameter), while current is the flow.

 But the operating voltage of the wheel is different from the voltage that the motor is driven with, changing the game. Otherwise it would be much simpler.

I don’t know what the exact minute differences in magnetic fields and other data would be. But what makes this tricky is that bigger voltage wheels usually have a lower kv rating, so that instead of more speed we get more torque. Or somewhere in between. That makes the minute differences meaningless. And to my knowledge the exact kv ratings are only known for a few wheels, so in the end it wouldn’t even help us in comparing 100V and 134V EUCs.

On 3/24/2023 at 1:37 PM, The Brahan Seer said:

As mentioned previously above one day we really need to put all these wheels on a dyno, rolling road to get at least some comparison.

Why though? Even if wheel A has a higher peak power output, wheel B might have a firmware that makes it easier for the rider to tap in to that power. So the dyno winner can just as well be the loser in practice, and we’re back to square one (after a few guys have bought the dyno winner thinking that they would be able to accelerate faster, yet losing the races).

On 3/24/2023 at 1:37 PM, The Brahan Seer said:

So I am still non the wiser

If you’re looking for a wheel for racing, check what the other racers are using. I’d imagine they know pretty well what works.

 If you’re not going to race with the wheel, all current EUCs are already powerful enough. Just spare enough speed headroom (to free spin speed for the lack of a better measure) and you’re golden. No point in letting all this get to you.

 

On 3/24/2023 at 4:13 PM, JeremySPFF said:

Yes, my subjective view is that I look for objective information to make a decision. This is what I am trying to explain.

Yes, and we have heard you loud and clear. Please mirror us back to ourselves, what has been the general  response you’ve gotten to your requests so far?

On 3/24/2023 at 4:13 PM, JeremySPFF said:

The problem is you don't understand the difference between objective and subjective.

Right… 

On 3/24/2023 at 4:13 PM, JeremySPFF said:

objective data is measurable.

And to make it worthwhile it also needs to be repeatable. And that’s where the data that you call objective fails. And I think that’s the reason why people haven’t put much effort into measuring it.

On 3/24/2023 at 4:13 PM, JeremySPFF said:

Subjective is when Kuji says 'this feels fast to me'. I cannot measure how it feels to him.

Unless you’re going to the actual races, feeling fast is more important than being fast. You’re not clocking your accelerations during your commute, so the actual measurements would be meaningless. Instead, if you want to feel the acceleration, you need a wheel that indeed feels subjectively faster.

On 3/24/2023 at 4:13 PM, JeremySPFF said:

I am so glad you asked. Eevee's just posted a video with some good objective information and testing.

I watched the video earlier, and scanned through it again, but couldn’t find any acceleration tests. I specifically asked about how would you organize an acceleration test.

On 3/24/2023 at 4:13 PM, JeremySPFF said:

unless you don't understand what that means.

If we’re going down this route, maybe I should ask you whether you understand what acceleration means?

On 3/24/2023 at 4:13 PM, JeremySPFF said:

You can always tell someone is losing an argument when they try to put the other person down.

Right. I guess we can tell someone wins the argument when they bail?

 Look, the reason why this has gone back and forth without going anywhere is that you requested data, but you were told that such data doesn’t exist and wouldn’t be useful even if it did. But you weren’t satisfied with that answer, and disagreed with the facts that experienced riders and people knowledgeable in physics told you. How do we go forward from there?

[The Brahan Seer]

2 hours ago, mrelwood said:

I was taught the other way around, voltage being the potential (large hose diameter), while current is the flow.

Current is the rate at which electrons flow past a point in a complete electrical circuit. At its most basic, current = flow. 

So the analogy still holds. But as you say doesn't really help us anyway. So its a moot point.

See below for confirmation:

https://www.freeingenergy.com/understanding-the-basics-of-electricity-by-thinking-of-it-as-water/

https://www.fluke.com/en-gb/learn/blog/electrical/what-is-voltage

https://www.fluke.com/en-gb/learn/blog/electrical/what-is-current