I only have this tracking right now
We made a uphill tour in a mountain here in austria
The motors were just slightly warm and ubox had 37degree as far as i can remember from the real life data of the app (it was not a hot day) the heat sink seems to work well
I think you need to double the wh because the bluetooth dongle only records one side of the ubox
how fast are u guys going 55km/t or somthing shiit maan im shoothing for 45km/t with hella tourge + im in a flat contry with almost no hills so 16s 140kv motor is just for keeping all eletronics cool
What esc enclosure are you using?
Iām working on a 16S build and planning on running 190kv 6384.
Curious since your post is from a while ago what happened with your 18S 190kv?
Worked fine, blew up, shot you into space?
yes
Sounds like what I thought. Boom!
nah, iāve always run 190kv on 18s
always blown up escs but not cause i run 190kv
Here is something interesting I saw on the bench today:
I measured this with an external shunt type meter at the battery. Same ESC
95% duty cycle, no load current on a 63100 190kv motor from Torque Boards.
12s 190kv - 3.52A @ 46.8v = 164w
18s 190kv - 4.67A @ 70.2v = 327w
So it takes 163w in waste heat just for the privilege to run 190kv on 18s at full RPMs due to iron losses.
What about copper losses? High Kv motors have lower resistance so have less copper losses at the same current. If we assume that iron losses match RPMs when the motor is the same size, and we choose a motor that reaches the same RPMs at 18s as a 12s 190kv motor, then we end up at 130kv.
Using the resistance values from the Lacroix motors, we can calculate copper losses at 100A
So if two dual motor boards were geared for 40mph top speed, and both drawing 100A at full speed, the 18s 130kv setup would be putting down ((455-343)x2=) 224 additional watts to the wheels compared to an 18s 190kv setup. The 18s 190kv setup would be pumping 224 more watts into heating the motors vs the 18s 130kv.
I donāt have a dyno to test all of this in the real world, but I think itās why companies who do have some sort of dyno choose 130kv for 18s and 190kv for 12s. Longer range, less motor heat and more power to the wheelsā¦ however this is all at full power and full RPMs. I wonder if running 18s 190kv at 50% duty and 20A would be more efficient than 18s 130kv at 50% duty and 20A.
Need someone smarter than me to double check all this lol @Dinnye @Pedrodemio
EDIT: Waitā¦ if you used the āExperimentsā feature in the VESC tool, and checked iron losses at say 5% duty cycle steps for various motors, factored in the winding resistance, then figured out how many mechanical watts are needed to overcome the rolling resistance, wind resistance and hill resistance, factoring in gearing for torque, you would basically have the esk8 equivalent of the Grin motor simulator.
Is it really that easy? Is a mechanical dyno not needed? Where does magnetic saturation come into play?
sooooooooo Iām runnin hot
makes sense
Heās not comparing 18S 190KV. Would be interesting to see tho. Would want to factor in gear ratio adjustment too tho.
I suppose something this doesnt factor is with the extra RPM, you can use a larger gear reduction for the same top speed to have a higher effective torque output? Im just pretengineering this in my brain. Iām gonna run 205kv motors on 16s just so I can have a crazy 6.42:1 reduction for 165mm tires. should have dummy torque but I could also easily be missing something.
Yes and no I think.
190kv motor has lower torque per amp than a 130kv motor. Itās a linear relationship so the gearing compensates rather than adds.
so youāre telling me all of this poopoo ive gone through is meaningless and I shouldve just gotten lower kv motors?
I have no idea lmao. Itās something Iāve been thinking about for a long time and feel like Iām finally starting to put the picture togetherā¦ but it just seems like there are a few things Iām missing.
Either way, 100-200w losses on a 5,000w to 7,000w board isnāt something you are likely to notice in the āseat of your pantsā feelā¦
i need hoyt to make their dum board dyno so we can find the dumbest way for moar torq
Those looks about right
Makes no sense running a 190 Kv motor at 18S, for them to be efficient at that point you have to run them at a power level far above what can dissipate
The dyno part is kinda yes kinda no but I havenāt got to the point of building one yet, while those analytical calculations get close, everything changes in real life, copper resistance increases quite a bit with the motor at boiling point, which isnāt uncommon with some riders that really push it, you can add 50% more resistance at least, magnet flux goes down, so your motor Kv is actually changing all the time and so on
But the biggest twin a dyno allows is to make a thermal model, with that you can really predict quite well what will happen, like the trip simulator from Grin do, you can even input our motors there with just the measurements you took, itās just the thermal model that is lacking, but you can also approximate from some data they have on eskate hub motors and real life rides, put a path you know and have logs and compare
comparing the output power to make it fair the 18s 190kv is 46% faster rpm. Thatās 46% more power with only 32% more losses making it more efficient than the slower setup at that high power output
Even at lower power output the faster motor can be more efficient. The only time i think will end up less efficient is at low power output and high speed.
Torque to heat is the same for all motors of a certain design as long as the same amount of copper regardless of kv. High kv is low resistance but low kt and low torque and it all balances in the end.
I think the big variable in the comparison is when the 130 kv magnetically saturates first, which it will. Assuming it saturated at 68 amps and the 190kv at 100 ampsā¦ultimately u have the same (efficient) max torque output there and the high kv motor has more rpm to convert to torque and can produce higher max torque or power
This is great to hear. My pretengineer thought process was on the right track. Not sure how a low kv motor would handle 140 phase amps where as the 205kv should do much better in that regard.
Iām recently into this question as doing 86v and therefore require a really low kv motor to end up with a slow enough rpm. Itās ideal: The low kv is more torque per amp and get to throw a bunch more speed into the equation with a lot of gearing. Speed is generally more efficient to produce out of a motor than torque.
But as revealed in other thread here the required bigger gearing for higher voltage and higher rpm is going to be a loss with the required smaller motor pulley inefficiency
As linked above the grin simulator is a great revealer
And on the saturation part, the dyno will answer that, but there is a easy way anyone can do
Hook a lever to a motor and use a scale to rotate that lever, feed DC current into a phase on the motor and see how much force you need to skip a step, increase current and repeat
Plot current vs force and see where it starts to become non linear
Might be worth having the motor underwater or with constant water flow on it, doubt it will last more than a few seconds at higher currents levels without it
