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Marty Backe

126-Volt Nikola

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Nice math! Higher voltage means less parallel blocks which negates exactly the lower current requirement. So the cells are stressed exactly the same (for a given power requirement and battery size) regardless of the battery configuration.

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Indeed, that is true. I find myself guilty for spreading a long lasting myth that can be killed with such simple math.

Although, I do wonder wether there are factors that could make the outcome differ from the steady state of the above calculations. Capacitors that provide transient power, power switching between coils, how fast the cell voltage drops under load, etc.

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13 hours ago, BleepBloopBlop said:

For a set number of cells at a given power level you will have the same percentage of voltage sag with a 126V wheel as a 84V wheel. Going to a higher voltage array doesn't mitigate voltage sag. 

For example:

MJ1 cell at 10A draw produces about 3.5V near the top of its charge.

30S4P pack at this cell draw will be at 105V and 40A for a power output of 4200w

20S6P pack at this cell draw will be at 70V and 60A for a power output of 4200w

 

Both of these packs have the same percentage of battery voltage sag while output the same amount of power. This won't change when comparing the same number of cells in different series and parallel configurations. There will be less loss through the wiring at higher voltage for a given power transmission.

The watts number doesn't say much about how the wheel feels.  Amps = torque, volts = speed.  So the 105V pack will have less torque than the 70V pack.  The real question is if the rider can feel it.  Maybe 40amps is more than enough, but doubtful as I've seen even KS wheel report more than 40A in certain instances.  It is already known that the GW amps number reported is inaccurate.  If there is a limit of 10amp draw per pack then they both have the same voltage drop when under load.  But the lower voltage will cut out at a lower speed where as the higher voltage will still stay running.  

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Posted (edited)

What I've noticed is that Gotway wheels use significantly more battery when they're pushed to their upper limits in terms of speed.  Would a higher voltage wheel mitigate that?

e.g. When I'm riding at 28mph on my 84v MSX I can literally watch my battery dying.  Would riding a 100v/126v wheel not experience this until it hit it's limit of around 40mph or would it still suffer the same battery drain at around 28 and even worse at 40?

 

If having a higher voltage wheel would increase the speed in which the intense battery drain happened at that would be reason enough to buy one for me.

Edited by MrRobot

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28 minutes ago, MrRobot said:

What I've noticed is that Gotway wheels use significantly more battery when they're pushed to their upper limits in terms of speed.  Would a higher voltage wheel mitigate that?

e.g. When I'm riding at 28mph on my 84v MSX I can literally watch my battery dying.  Would riding a 100v/126v wheel not experience this until it hit it's limit of around 40mph or would it still suffer the same battery drain at around 28 and even worse at 40?

 

If having a higher voltage wheel would increase the speed in which the intense battery drain happened at that would be reason enough to buy one for me.

Well yes, it would mean less current required to attain said speed; (volts + amps = watts). There are drawbacks to this however; there’s only a finite amount of space in an EUC, meaning your total available capacity will be lower. 

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Posted (edited)
2 hours ago, MrRobot said:

What I've noticed is that Gotway wheels use significantly more battery when they're pushed to their upper limits in terms of speed.  Would a higher voltage wheel mitigate that?

No, it mostly would not mitigate that.

The problem at high speeds is wind resistance (drag). Drag is the main power draw in EUC riding, and it goes up like crazy with speed (double the speed, 4x the drag). Same reason why you get insane range when you go really slowly or with lighter riders (which are smaller and have much less wind resistance).

So while high voltage wheels might (or might not) be a bit more efficient at high speeds, that still doesn't solve the main problem that high speeds simply means high drag losses. The Gotways are faster than others and that's where you really feel the drag killing your battery. That problem won't go away, no matter the internal electronics, high voltage, low voltage, whatever. You simply have a higher power draw when riding due to the drag, so your battery empties quicker.

Try seated riding for reducing your wind resistance losses:)

Edited by meepmeepmayer
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2 hours ago, MrRobot said:

What I've noticed is that Gotway wheels use significantly more battery when they're pushed to their upper limits in terms of speed.  Would a higher voltage wheel mitigate that?

e.g. When I'm riding at 28mph on my 84v MSX I can literally watch my battery dying.  Would riding a 100v/126v wheel not experience this until it hit it's limit of around 40mph or would it still suffer the same battery drain at around 28 and even worse at 40?

 

If having a higher voltage wheel would increase the speed in which the intense battery drain happened at that would be reason enough to buy one for me.

Just to be clear, any wheel will use significantly more power while riding fast. The phenomenon is not limited to Gotway :) 

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22 minutes ago, meepmeepmayer said:

No, it mostly would not mitigate that.

The problem at high speeds is wind resistance (drag). Drag is the main power draw in EUC riding, and it goes up like crazy with speed (double the speed, 4x the drag). Same reason why you get insane range when you go really slowly or with lighter riders (which are smaller and have much less wind resistance).

So while high voltage wheels might (or might not) be a bit more efficient at high speeds, that still doesn't solve the main problem that high speeds simply means high drag losses. The Gotways are faster than others and that's where you really feel the drag killing your battery. That problem won't go away, no matter the internal electronics, high voltage, low voltage, whatever. You simply have a higher power draw when riding due to the drag, so your battery empties quicker.

Try seated riding for reducing your wind resistance losses:)

 

3 minutes ago, Marty Backe said:

Just to be clear, any wheel will use significantly more power while riding fast. The phenomenon is not limited to Gotway :) 

 

Hmmm I was under the impression that the KS18XL does not suffer from this at it's max speed?  Or at least not nearly the same level of drain.

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4 hours ago, eddiemoy said:

The watts number doesn't say much about how the wheel feels.  Amps = torque, volts = speed.  So the 105V pack will have less torque than the 70V pack.  The real question is if the rider can feel it.  Maybe 40amps is more than enough, but doubtful as I've seen even KS wheel report more than 40A in certain instances.  It is already known that the GW amps number reported is inaccurate.  If there is a limit of 10amp draw per pack then they both have the same voltage drop when under load.  But the lower voltage will cut out at a lower speed where as the higher voltage will still stay running.  

This isn't true @eddiemoy if the wheels are setup to have the same top speed. The reason you believe this is the current line of 84V and 100V wheels have the same KV, so the 84V wheel is essentially geared lower. If both wheels are outputting the same amount of power from the battery pack with the same KV motor, the wheel with lower voltage and more amps will will feel stronger at acceleration, but have a lower top speed. 

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1 hour ago, MrRobot said:

Hmmm I was under the impression that the KS18XL does not suffer from this at it's max speed?  Or at least not nearly the same level of drain.

well, it is a thinner wheel with a much smaller tire and less top speed.. otherwise they should be very similar.. perhaps you are thinking that because battery percentage calculated by voltage gives kingsong a boost over gotway because they allow the batteries to drain more.. both could say you have 20% battery remaining but you would in reality have a higher battery percentage on the gotway, it just wouldn't allow you to utilize as much

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Posted (edited)
1 hour ago, MrRobot said:

Hmmm I was under the impression that the KS18XL does not suffer from this at it's max speed?  Or at least not nearly the same level of drain.

There's a huge difference in drag between 45-50kph and 55kph. Gotways are faster so the drag quickly reduces the Wh/mile efficiency.

22 minutes ago, BleepBloopBlop said:

This isn't true @eddiemoy if the wheels are setup to have the same top speed. The reason you believe this is the current line of 84V and 100V wheels have the same KV, so the 84V wheel is essentially geared lower. If both wheels are outputting the same amount of power from the battery pack with the same KV motor, the wheel with lower voltage and more amps will will feel stronger at acceleration, but have a lower top speed. 

In theory that's all right. But then why does the 100V Nikola have better acceleration and top speed, as found in @Marty Backe's blind test? So the firmware or something else has to play a role there for practical behavior.

I'd be very interested to separate the cold hard motor facts as you described and whatever else leading to the practical results we have.

Edited by meepmeepmayer
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23 minutes ago, meepmeepmayer said:

There's a huge difference in drag between 45-50kph and 55kph. Gotways are faster so the drag quickly reduces the Wh/mile efficiency.

In theory that's all right. But then why does the 100V Nikola have better acceleration and top speed, as found in @Marty Backe's blind test? So the firmware or something else has to play a role there for practical behavior.

I'd be very interested to separate the cold hard motor facts as you described and whatever else leading to the practical results we have.

It is hard to trust seat of the pants feeling.  They should have the same acceleration because they have the same number of parallel packs, so same amps.  the only difference between the two wheels is voltage which is higher top speed.  

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48 minutes ago, BleepBloopBlop said:

This isn't true @eddiemoy if the wheels are setup to have the same top speed. The reason you believe this is the current line of 84V and 100V wheels have the same KV, so the 84V wheel is essentially geared lower. If both wheels are outputting the same amount of power from the battery pack with the same KV motor, the wheel with lower voltage and more amps will will feel stronger at acceleration, but have a lower top speed. 

Isn't that what I said?  I was referring to your 4pack vs 6pack example.  amps=torque and voltage =speed.  lol

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16 hours ago, Marty Backe said:

I feel confident in my blind acceleration/stopping test of the 84v & 100v Nikola's. The 100-volt mode had better acceleration and braking.

Unless the wheels are different, maybe the 100V pulls more amps due to the new board?  It cannot be faster if they are pulling the same amps.  If they are pulling the same amps, they really should be the same.   

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5 minutes ago, Arbolest said:

If a control board needs to provide a momentary burst of acceleration, it is basically just going to expose the motor to the full voltage of the battery and let those electrons flow. Because the motor doesn't provide very much resistance at ALL (it's basically just a long piece of wire), this will allow a stupendous amount of current to flow. And guess what? The battery packs that we have in our modern wheels are ALL easily capable of providing this current, in either the 84v or 100v flavors.

How many amps are we talking about then?

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4 minutes ago, ir_fuel said:

How many amps are we talking about then?

Momentarily? Think welding level amps and you're in the ballpark.

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Also, I guess it was a really sideways way of saying it, but all I was trying to say with that rant is that when people here talk about Amps = torque, they seem to be confusing the number of Amps that the wheels are actually using and the number of sustained Amps the battery packs are capable of providing for long periods ON PAPER, and they are NOT the same number.

Edited by Arbolest
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On 8/3/2019 at 11:09 AM, meepmeepmayer said:

Sure, let's talk about motor minutia!

@esaj @Chriull Does x% higher voltage mean x% higher top speed? If they use the same motor as in the 84V or 100V wheels, how fast will it go? You can predict that, right?

Unfortunately, don't think it will be that simple even if total motor power does increase linearly like that.

Wind resistance increases exponentially with speed. I thought I've heard someone iike esaj or chriull on here mention that wind resistance is the one of the biggest factors with EUCs for increased power consumption at higher speeds. Indeed a person standing does not make a very aerodynamic profile.

Regardless, the new power possibilities are exciting though!

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@Blueblade By top speed I meant the no-load, freewheeling speed (just the zero torque speed). So only looking at the properties of the motor itself. Of course wind resistance will ruin everything in reality, but I still haven't given up on EUCs on the moon;) That's how that post was meant.

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3 hours ago, Arbolest said:

Ok guys, this has been bugging me for a looooong time in these conversations. Unless the 100 volt wheel is running with an absurdly low number of packs in parallel, the100 volt wheel will always win. 

While everyone here has been yelling about how Amps = torque and Volts = speed and so the wheel with the most packs in parallel will obviously have more torque and grunt, they seem to somehow be missing the fact that that's not the whole story behind what is going on in one of these systems...

Remember, the most important thing to consider here, above ALL ELSE, is V=IR. (voltage = current x resistance)

In our situation, all things being equal, an 84v battery pack's maximum power output will never be as high as a 100v battery pack's.

The total amount of current that is going to flow through the motor only really depends on the voltage the motor is exposed to and its internal resistance. Now, assuming the motors on the 84v and 100v wheels are actually the same, then as long as the battery packs can both source the required current, the 100v pack will ALWAYS be able to generate more theoretical torque in that motor!

And the 100v pack can DEFINITELY source the current. The theoretical instantaneous current (amps) output of these battery packs is WAY higher than what is commonly quoted here. The ~10 amps per cell number that gets thrown around is at the high end of their nominal constant discharge rating, not what they are actually capable of delivering when they are essentially shorted (across, say, the motor). All the control boards in our wheels do to regulate the motor's power output and speed (simplified explanation of course) is regulate the voltage that the motors are exposed to. If a control board needs to provide a momentary burst of acceleration, it is basically just going to expose the motor to the full voltage of the battery and let those electrons flow. Because the motor doesn't provide very much resistance at ALL (it's basically just a long piece of wire), this will allow a stupendous amount of current to flow. And guess what? The battery packs that we have in our modern wheels are ALL easily capable of providing this current, in either the 84v or 100v flavors.

Everyone seems to be getting hung up on the debate between the 84v and 100v wheels at the "well the 84 volt wheels have more cells in parallel and will therefore provide more Amps" point. And while yes, the more batteries you have in parallel, the higher your theoretical current cap is going to be, you have to remember that in the highest-demand scenario we can put our wheels in, a single 84 volt (20s3p) battery pack can easily take care of it. They can provide way more current than our control boards will ever ask for, so it just seems silly to me that people are debating so vigorously over the supposed difference in torque between having 4 packs in parallel and 6 packs in parallel. Range anxiety aside, we don't even really need that many.

 

I guess that in order to put this to rest we need an example... 

Imagine two identical wheels. Same motors, same over-engineered control boards, same wiring, same shell, same pedals, yada yada... Now, one wheel has a regular old 84v 1600wh battery pack. The other wheel has an 84v battery pack that is 1000 times larger (with 1000 times as many cells), measuring in at 1,600,000 wh :wub:. It can provide 1000 times as many amps as the smaller battery pack. Now, let's say that the giant battery pack is magical and has exactly the same mass and dimensions as its 1600wh little brother.

Which of these wheels "has more torque"?

Will either wheel actually perform any differently?

If I were to use my regular old run-of-the-mill 1600wh wheel and race against my evil twin who is riding the 1,600,000wh wheel, is my evil twin going to take off like a bat out of hell and accelerate 1000 times faster than me? 

No. No he will not. I don't think there would be any difference at all between the performance of my regular old 1600wh wheel and the magical one. The reason is that I can have all of the current capacity in the universe, but if my electrical circuit doesn't generate a demand for it, then it's wasted and will never get used. 

 

I reiterate from above:

In our situation, all things being equal, an 84v battery pack's maximum power output will never be as high as a 100v battery pack's.

V=IR

 

 

Well stated :cheers: And I'm sticking by my objective "blind" comparison test - the 100-volt wheel does indeed have better acceleration and braking.

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3 hours ago, meepmeepmayer said:

@Blueblade By top speed I meant the no-load, freewheeling speed (just the zero torque speed). So only looking at the properties of the motor itself. Of course wind resistance will ruin everything in reality, but I still haven't given up on EUCs on the moon;) That's how that post was meant.

Ah, ok, yes makes perfect sense.  (And I believe they do, more or less.  Motors being rated in kv=, K of RPM per v of input)  They tend to draw more current under load, the motor "tries harder" to get to the speed it "wants" to be at given the voltage.  With electric rc airplanes, you can often get more power out of the same motor and battery by putting a bigger prop on, within reason of course, (but then the battery drains faster, and the whole system needs to be capable of the increased current demand because the motor tries to spin the bigger prop at the same rpm).

Same happens with higher voltage too, motor wants to turn at a faster rpm with more voltage applied, drawing more current to do it (at full throttle anyway)

Adding 1 cell to the battery pack in series, the plane goes faster at full throttle and drains the pack faster: more current draw, but no more Ah capacity in the battery, only a voltage increase.

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