ElectricMotorcycleForum.com
Makes And Models => Zero Motorcycles Forum | 2013+ => Topic started by: Lecram on May 05, 2015, 02:09:12 PM
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When my bike is in sports mode and I want to accelerate, the bike starts slowly and acceleration increases at higher speeds. Especially with a passenger on the bike, I am barely faster away from the traffic lights than the cars. My KTM is much faster at low speeds. It seems that the Zero has reduced torque at low speeds.
is that normal? And is that adjustable?
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Think it may be a limit of the motor controller
S & DS Gen 4 size 4 420A max current to motor.
DS Acceleration, 0-60 mph (0-100 km/h) 9.4=5.2 seconds 12.5=5.7 seconds 12.5+PT=6.4 seconds
S Acceleration, 0-60 mph (0-100 km/h) 9.4=4.8 seconds 12.5=5.2 seconds 12.5+PT=5.8 seconds
SR Gen 4 size 6 660A max current to motor.
Acceleration, 0-60 mph (0-100 km/h) 12.5=3.3 seconds 12.5+PT=3.9 seconds
Zero may also be limiting max torque at take off for safety and liability reasons, wish they would allow an insane mode unlock like Tesla has :D
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I would suggest you quantify your acceleration to see how far off spec the bike is. You can use your cell phone to capture the speedometer while doing accelerations and then analyze the frames after to determine your times.
Remember to take into account your weight and the PT (if you have one) when comparing to the spec.
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Lecram, 0-100 km/h in 6,4 is not exactly slow.
If in doubt, time your bike.
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I can sense a very slight delay on my DS from a stop (0-10MPH?) but after that it ratchets up quickly. I knew that I was obviously not going to get the fastest bike in the Zero lineup so I did not expect that much. In sport mode I am getting zero to sixty in around 5 seconds no problem. That is faster than a Mustang GT so I don't think it is particularly slow.
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... That is faster than a Mustang GT so I don't think it is particularly slow.
um, no. http://www.0-60specs.com/ford-mustang-0-60-times/ (http://www.0-60specs.com/ford-mustang-0-60-times/)
:D
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When my bike is in sports mode and I want to accelerate, the bike starts slowly and acceleration increases at higher speeds. Especially with a passenger on the bike, I am barely faster away from the traffic lights than the cars. My KTM is much faster at low speeds. It seems that the Zero has reduced torque at low speeds.
is that normal? And is that adjustable?
See the article that Ted wrote up here, and pay close attention to the comments.
https://evmc2.wordpress.com/2014/07/07/motor-starting-torque-stall-torque-and-motor-types/ (https://evmc2.wordpress.com/2014/07/07/motor-starting-torque-stall-torque-and-motor-types/)
The Dyno chart from motorcycle consumer news shows that the motorcycle has relatively constant torque from 1000 RPM (their dyno lower limit) up to 3200 RPM (that is from 17mph up to 55mph) .. the flatness of the torque curve remains even at lower RPM.
http://www.motorcycleconsumernews-digitalmagazine.com/mcnews/september_2014d?pg=20#pg22 (http://www.motorcycleconsumernews-digitalmagazine.com/mcnews/september_2014d?pg=20#pg22)
The "slow" acceleration at lower speeds is purely a human perception, not an imposed limitation on the vehicle.
Cars typically have a first gear that will shift at around 20mph when casually accelerating from a stop, when they shift, the wheel torque drops and thus acceleration also decreases for the same throttle position .. in the electric you don't shift, you just keep accelerating. I believe humans perceive the acceleration of the bike becoming faster, but really it is just faster in comparison to your point of reference, vehicles that have to shift.
-ryan
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Thanks Ryan, but it's for sure not a perception. I own a KTM 990, too, and this bike will lift it's frontwheel, even at 3rd gear. It's way faster from standstill than the Zero. A VW T4 was almost as fast as my DS.
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Lecram,
See this topic
http://electricmotorcycleforum.com/boards/index.php?topic=4635.0 (http://electricmotorcycleforum.com/boards/index.php?topic=4635.0)
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I just learned a bit ago we have been all wrong about the amperage rating of the gen4 systems. Look at this PDF on page 2. 96V to 120V size 4 is only 300A that is unless we are using the 72v to 80v controller whereas the current is still 350A (not counting burst). http://www.sevcon.com/media/2461/Gen4%20Aug%202013%20web.pdf (http://www.sevcon.com/media/2461/Gen4%20Aug%202013%20web.pdf)
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I just learned a bit ago we have been all wrong about the amperage rating of the gen4 systems. Look at this PDF on page 2. 96V to 120V size 4 is only 300A that is unless we are using the 72v to 80v controller whereas the current is still 350A (not counting burst). http://www.sevcon.com/media/2461/Gen4%20Aug%202013%20web.pdf (http://www.sevcon.com/media/2461/Gen4%20Aug%202013%20web.pdf)
The peak current is 360A for 10 secs. That's what it should deliver when accelerating from standstill
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I just learned a bit ago we have been all wrong about the amperage rating of the gen4 systems. Look at this PDF on page 2. 96V to 120V size 4 is only 300A that is unless we are using the 72v to 80v controller whereas the current is still 350A (not counting burst). http://www.sevcon.com/media/2461/Gen4%20Aug%202013%20web.pdf (http://www.sevcon.com/media/2461/Gen4%20Aug%202013%20web.pdf)
The S / DS use the G8035 Size 4, the SR uses the G8055 Size 6. These controllers top at 116VDC, despite the nominal 80V rating.
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I just learned a bit ago we have been all wrong about the amperage rating of the gen4 systems. Look at this PDF on page 2. 96V to 120V size 4 is only 300A that is unless we are using the 72v to 80v controller whereas the current is still 350A (not counting burst). http://www.sevcon.com/media/2461/Gen4%20Aug%202013%20web.pdf (http://www.sevcon.com/media/2461/Gen4%20Aug%202013%20web.pdf)
The peak current is 360A for 10 secs. That's what it should deliver when accelerating from standstill
The peak current for the 80V Gen4 is
Size2: 180A (2013 XU)
Size4: 350A (FX, S, DS)
Size6: 550A (SR)
From page 3-9 of the user manual:
http://www.thunderstruck-ev.com/Manuals/Gen4_Product_Manual_V3.0.pdf (http://www.thunderstruck-ev.com/Manuals/Gen4_Product_Manual_V3.0.pdf)
However on page 4-3 It goes into more detail with a graph that shows that "boost" region allows for 120% of the short term current for up to around 30seconds, which ends up providing the following current limits
Size2: 216A (they actually boosted that boost on the size2 up to 250A)
Size4: 420A
Size6: 660A
-ryan
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The peak current is 360A for 10 secs. That's what it should deliver when accelerating from standstill
Lecram, it's a limitation of the ESC. Full current (full torque) at 0 rpm would induce great current ripple because the BEMF is very low. To have full current, you would have to increase ESC switching freq a LOT, but that means a lot of additional heat (=burned MOSFETs)
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The peak current is 360A for 10 secs. That's what it should deliver when accelerating from standstill
Lecram, it's a limitation of the ESC. Full current (full torque) at 0 rpm would induce great current ripple because the BEMF is very low. To have full current, you would have to increase ESC switching freq a LOT, but that means a lot of additional heat (=burned MOSFETs)
in fact the Sevcon Gen4 does provide full current at 0RPM, until temperatures get up and the controller starts reducing current to maintain operating temperatures.
-ryan
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in fact the Sevcon Gen4 does provide full current at 0RPM,
If people are complaining that the bike is slow at very low speeds, I think the ESC is not providing full torque at 0rpm.
Can the Sevcon do that? Perhaps.
Another place to look for answers is the MBB settings (Main Bike Board):
http://electricmotorcycleforum.com/boards/index.php?topic=2925.0 (http://electricmotorcycleforum.com/boards/index.php?topic=2925.0)
http://electricmotorcycleforum.com/boards/index.php?topic=4357.0 (http://electricmotorcycleforum.com/boards/index.php?topic=4357.0)
Good luck guys! ;)
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The peak current is 360A for 10 secs. That's what it should deliver when accelerating from standstill
Lecram, it's a limitation of the ESC. Full current (full torque) at 0 rpm would induce great current ripple because the BEMF is very low. To have full current, you would have to increase ESC switching freq a LOT, but that means a lot of additional heat (=burned MOSFETs)
Actually the BEMF voltage doesn't have an influence on the current ripple. Only the motor (winding) inductance does. The very low BEMF just means that a lot of current is needed to get some active power. But from the ESC limitations still full torque should be available...
Thus I also think it's rather a configuration limitation.
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The peak current is 360A for 10 secs. That's what it should deliver when accelerating from standstill
Lecram, it's a limitation of the ESC. Full current (full torque) at 0 rpm would induce great current ripple because the BEMF is very low. To have full current, you would have to increase ESC switching freq a LOT, but that means a lot of additional heat (=burned MOSFETs)
Actually the BEMF voltage doesn't have an influence on the current ripple. Only the motor (winding) inductance does. The very low BEMF just means that a lot of current is needed to get some active power. But from the ESC limitations still full torque should be available...
Thus I also think it's rather a configuration limitation.
BEMF voltage does influence current ripple
The formula is V= L di/dt
http://en.m.wikipedia.org/wiki/Inductance (http://en.m.wikipedia.org/wiki/Inductance)
In this case, V (applied to the motor winding) = V(battery) - V(BEMF). If "dt" and "L" are constant (constant switching frequency= constant dt and L is constant), then "di" varies with V, which varies with V(BEMF).
0 rpm => 0 V(BEMF) => max "V" => max "di" => possibility of lower phase current => lower standstill torque
But I agree that a possible configuration limitation might exist.
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RNM, at low switching speeds, the DC resistance of the copper windings dominates the inductance in limiting how much current you can drive through the motor; at some transition speed, inductance becomes a factor and you can no longer get maximum current through the windings (or, stated equivalently, BEMF starts to rise), which reduces the torque the motor can put out. That's called the "field weakening" point; IIRC it occurs around 3500 rpm on my bike (a 2014 SR), which is somewhere around 60 mph. BEMF is not a factor at low speeds, DC resistance of the copper wire is.
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RNM, at low switching speeds, the DC resistance of the copper windings dominates the inductance in limiting how much current you can drive through the motor; at some transition speed, inductance becomes a factor and you can no longer get maximum current through the windings (or, stated equivalently, BEMF starts to rise), which reduces the torque the motor can put out. That's called the "field weakening" point; IIRC it occurs around 3500 rpm on my bike (a 2014 SR), which is somewhere around 60 mph. BEMF is not a factor at low speeds, DC resistance of the copper wire is.
DC winding resistance is another component of the motor time constant (L/R), which let's us calc the current rise and fall.
See the spreadsheet in this link:
http://www.endless-sphere.com/forums/viewtopic.php?f=30&t=29852&start=15#p433095 (http://www.endless-sphere.com/forums/viewtopic.php?f=30&t=29852&start=15#p433095)
2 notes for the spreadsheet:
- Time constant varies a lot from motor to motor
- "Applied Voltage" on the top-left is the V (motor) = V (battery) - V(BEMF)
If you play a bit with it, you can see that having 0 BEMF or 50V BEMF, with a 100V battery , you get twice the current in the same time interval.
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I stand corrected Ted. Must have been looking at one of the V6 specs. :-[
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I recently noticed my SR would start slowly off the line but after a second or two then it would take off.... Through the App I put everything thats on CUSTOM mode to 100% except the coasting regen to 0%... I noticed a lot more torque off the line in the new Custom mode, even more THAN Sport mode...... Im wondering if if I accidentally lowered the numbers in SPORT mode that I didnt know I did or could do???? ???
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Lecram you'll need a DSR :P