why if there is enough movement from your wrist to power a watch why shouldnt all the vibrations are carving of the board maybe add an extra 5% to your battery life
Think about how small of a battery a watch needs…
5 Likes
Those two things aren’t even on close to the same scale lmao
The watch you’re speaking of probably draws milliwatts of power with a <3wh battery.
In comparison we are drawing thousands of watts from a 200wh< battery lol my battery is 270 wh and it is a small one. The one in my own smartwatch is 2wh
Vibrations wouldn’t even power headlights
1 Like
My watch claims it works but even after a nice “run” in my bedroom it only recharges 5 - 7% which is nothing.
3 Likes
theres the piezoelectric thing. could be easy to hook up but doubt youd get much. and youd need the electronics to transform it into a specific dc voltage the battery could take
but you could skip the battery
https://www.bing.com/videos/search?q=piezo+electric+light&view=detail&mid=7FB3E6ED18DC72B02B327FB3E6ED18DC72B02B32&FORM=VIRE
https://www.bing.com/videos/search?q=piezo+electric+light&&view=detail&mid=4A0BD5618AA94B5F5F344A0BD5618AA94B5F5F34&rvsmid=7FB3E6ED18DC72B02B327FB3E6ED18DC72B02B32&FORM=VDRVRV
BLDC Efficiency Control
Motor Current Control Throttle Variation
Control Loop Targets
Settings:
M= 100 = Throttle % Setting
K= 90 = Desired Efficiency % Setting
L= 500 = Desired Min Watts Available Setting
P= 4500 = Desired Max Watts Available Setting
Y= 120 = Max Motor Amps BLDC
Z= 95 = Max Duty Cycle %
Observables:
G= 48.2 = Battery Voltage
D= 16.94 = Back EMF Voltage
F= 0.025 = Winding Resistance Ohms (Lead to Lead)
Control Loop Targets:
A= XX.XXX = Battery Amps
B= XX.XXX = Motor Amps (BLDC)
H= XX.XXX = Throttled Wattage
N= XX.XXX = Desired Full Throttle Wattage
C= XX.XXX = Duty Cycle %
E= XX.XXX = Effective PWM Voltage
Where:
N=L
^this line sets the desired full throttle wattage at the minimum desired wattage value
&
if D>((sqrt(F) * K * sqrt(L))/(10 * sqrt(100-K))) then N=(-1) * ((100*(D^2) * (K-100))/(F * (K^2)))
^this line calculates whether there is enough back emf voltage present to allow the desired minimum full throttle wattage at or above the desired efficiency, and if there is, it adjusts the desired full throttle wattage to the value which achieves the desired electrical to mechanical conversion efficiency at the present rpm
&
if N>P then N=P
^this line adjusts the desired full throttle wattage to the maximum desired wattage setting if the wattage at desired efficiency exceeds the desired max wattage setting
&
if Y<((sqrt((D^2)+(4 * F * N))-D)/(2 * F)) then N=Y * (D+(F * Y))
^this line calculates whether the desired full throttle wattage exceeds the max motor amp setting, and if it does, it adjusts the desired full throttle wattage to a value which does not exceed the max motor amp setting
&
if Z<((50 * (sqrt((D^2)+(4 * F * N))+D))/G) then N=(G * Z * (G* Z-(100 * D)))/(10000 * F)
^this line calculates whether the desired full throttle wattage exceeds the max duty cycle setting, and if it does, it adjusts the desired full throttle wattage to a value which does not exceed the max duty cycle setting
&
H=(M * ((-1) * D * (M-100) * sqrt((D^2)+4 * F * N)+((D^2) * (M-100))+(2 * F * M * N)))/(20000 * F)
^this line calculates the desired full throttle motor amps, reduces the motor amps by a percentage based on throttle position, and then calculates the resulting desired wattage
&
C=((50 * (sqrt((D^2)+(4 * F * H))+D))/G)
^this line calculates the duty cycle control variable from the desired wattage, back emf voltage, winding resistance, and pack voltage.
&
E=G * (C/100)
^calulates pwm effective voltage
&
B=(E-D)/F
^calculates motor current
&
A=H/G
^calculates battery amps
&
repeat
Therefore:
Instantaneous Control Loop Targets:
A= 29.400 = Battery Amps
B= 75.264 = Motor Amps (BLDC)
H= 1417.10 = Throttled Wattage
N= 1417.10 = Desired Full Throttle Wattage
C= 39.049 = Duty Cycle %
E= 18.821618 = PWM Effective Voltage
———————-
For Illustration:
classical settings: 100% throttle, 300a battery amp limit, 300a motor amp limit, 33.2v battery, 850kv 0.0135ohm motor, 120mm tire diamter, 4:1 gear reduction, 2 motors
efficiency control settings: 100% throttle, 300a battery amp limit, 300a motor amp limit, 87.5% desired efficiency setting, 200w minimum electrical wattage setting, 9960w maximum electrical wattage setting, 33.2v battery, 850kv 0.0135ohm motor, 120mm tire diamter, 4:1 gear reduction, 2 motors
3 Likes
Thanks. Now I’ve got a math boner. Anyone have a pic of a classic HP scientific programmable calc to help finish the job?
1 Like
What if there was a way to travel back in time, but due to the possibility of creating a paradox and dissolving reality as we know it, you could only afford the ability to stop ONE USER from ever finding out about/joining the esk8 community. Decisions, decisions.
Unnnnnnfffff
1 Like
I hate to point out the obvious, but that’s a TI.
I ask for pics of Eva Longoria, and you post Reese Witherspoon. I’m not saying she’s not hot, but just not what I was looking for.
Gotta work with what ya got sometimes
I forgot to mention:
Results:
Efficiency Control: 32.07 miles per kilowatt hour
Current Control: 21.63 miles per kilowatt hour
Suppose I’m an electric skateboard vendor, and a previous customer asks me what options they have to achieve greatest possible range and efficiency on their electric skateboard when commuting in start and stop city traffic. The customer’s route to work features many stop signs and stop lights, so they start and stop very frequently, but they live in a completely flat area and don’t expect to encounter any hills. The board we are discussing has a battery which typically runs at 45.98V, (4) 81.42kv hub motors which are 0.136ohms and has 83mm diameter tires. The customer states their only requirements are they want to ensure the board is capable of 30mph top speed on flat ground, and aside from that requirement, they also want highest possible range and electrical to mechanical conversion efficiency while repeatedly accelerating at full throttle during their start-and-stop morning commute. Should I recommend “efficiency control” or the “classical algorithm” to achieve this customer’s requirements (at least 30mph top speed on flat ground and greatest possible range & conversion efficiency while repeatedly accelerating at full throttle in start and stop city commuter traffic)?
Stop Sign Separation Distance: 183.5 Meters
Full Throttle Acceleration Distance: 150 Meters
The 30mph-capable rider with “efficiency control” gets 148.25% as much range in start and stop traffic with stop signs placed 183.5 meters apart compared to the 30mph-capable “current control” rider, while both use full throttle acceleration for the first 150 meters of each acceleration cycle, followed by mechanical braking.
Efficiency Control: 51.62 kilometers = 32.07 miles per kilowatt hour
Classical Algorithm: 34.81 kilometers = 21.63 miles per kilowatt hour
The cheap china hub motor breaks?
2 Likes
How about an esk8 enclosure with an integrated heatsink that has fins that stick out a bit? One would couple the controller to the heatsink from the inside. Enclosure is still sealed and weatherproof. (maybe this had been done already idk)
Eboosted dose that with his enclosure.
I did a ghetto one.
3 Likes
So another weird thought. Would having a long threaded motor shaft that acted as shoulder bolts on a precision truck work? Btw, It’s nice having a place where smart people answer all my stupid questions. 
Could work (basic direct drive) but you’d need to thread one of the motor shafts backwards to keep it from wanting to undo itself on torquey starts. Are you assuming the motor pulley would screw on too?
Source: https://www.vesc-project.com/node/628
"I may be a little bit late to the game but this is of great interest to me.
I represent an undergraduate team (duke-ev.org) who builds ultra-efficient vehicles and we’ve been considering picking apart the vesc firmware to borrow some useful algorithms. I had made some edits to the firmware for a different project and I’ve gotten familiar enough with the firmware that I could probably get this implemented without too much difficulty. Benjamin has made it such a breeze to edit and flash firmware; I am very grateful.
Aside from the wildly unrealistic operating conditions our vehicle competes in, I do completely understand the appeal of this technique partly because I think about efficiency pretty much every waking moment. I think the big selling point is what you said earlier about how someone riding at partial throttle could theoretically match the acceleration proposed by your algorithm, but a human guessing what acceleration curve will make the optimal efficiency is never going to be as good as an algorithms forming a closed loop control to hit exactly the optimal efficiency. When we run our vehicle for record attempts, for example, we have 2-3 buttons which just apply the exact acceleration curves for optimal efficiency rather than using a thumb throttle.
I don’t want to make it sound like our ridiculous use case is the only reason you would use devin’s control, though. It’s definitely extremely valuable to just make the board run efficiently on its own without the user needing to tweak their thumb at just the right amount. Maybe you could make the argument that you’re splitting hairs on efficiency, but I could also make the argument that if you sell 1000 boards and each one runs 10 miles a day and saves 1% efficiency, over the course of a year that amounts to a lot of CO2 and $$$!
I’ll do some more research and further consider implementing this into the firmware. In the mean time, devin I may DM you for more theoretical details and I hope more people can see the value that this offers.
Gerry Chen"
^I hope if he doesn’t implement it someone else will… the easiest way to think of it is having a different motor current limit at each rpm, for constant efficiency during full throttle acceleration. When you “turn down” the efficiency setting you get more power and greater acceleration, and when you “turn up” the efficiency setting, you automatically get more range in start and stop riding, sacrificing some acceleration but not top speed, because more motor current becomes available the faster the motor turns. While accelerating through very low motor rpms, low efficiency is basically inevitable…