Apparently at some point the VESC had an ERPM limit of 60,000.
Calculating ERPM for different motors/voltages I am considering:
14s 12s 10s 8s
130kv 6734 5772 4810 3848
150kv 7770 6660 5550 4440
170kv 8806 7548 6290 5032
200kv 10360 8880 7400 5920
245kv 12691 10878 9065 7252
APS is my first choice for motors.
All APS 63mm motors have 12 poles.
14s 12s 10s 8s
130kv 80808 69264 57720 46176
150kv 93240 79920 66600 53280
170kv 105672 90576 75480 60384
200kv 124320 106560 88800 71040
245kv 152292 130536 108780 87024
Is this still the case? Can I only use the 130kv motor at 10s and below (and 150kv at 8s, etc)? Or is the VESC more capable now? I’m using the Torque VESC with 4.12 hw/3.34 fw.
How do I figure the safe kv for 12s with these motors? The formula given in the above link gives me an ideal kv of 115 which seems pretty low.
Depends which vesc you have
I’m using the Torque VESC with 4.12 hw/3.34 fw.
The formula is almost right. It´s
rpm x pole pairs - so usually 7 pole pairs.
A safe opinion on kV and voltages:
10s - 190 kV
12s - 170 kV
That sounds better! I guess that means I can halve all my erpm numbers then? Should make for a lot more viable motors!
That should mean I can use the 200kv motor I wanted at 12s and only hit a max of 53,280 erpm, so it won’t fry my vesc with its 60k limit!
Plus within the vesc you can set erpm limits so even with a really high kv motor you wouldn’t exceed
In that case the motor rpm would be bottlenecked by the erpm limit though, wouldn’t it?
Of course. But if you limited it to 60k erpm is it really a limit of it prevents your vesc from blowing a drv chip?
and you should use v for a full battery and not the nominal voltage
12s 18650: 50.4v
200kv = 10,080rpm
6 pole pairs, erpm = 60,480
Looks like I can just about make it, just throttling max rpm when the battery is full then. Keeping the 60k vesc limit should be enough for this to work, right?
Yes. It’s fine. That 200kv motor is probably less than 200kv
What makes you say that? It’s that a common occurrence?
one of my 190 kv motors is actually 200. the other 190 kv is 180.
Can anyone explain what happens while riding if you hit this limit? I recently had my diy build brake unexpectedly and throw me off and someone said this was the cause. would hitting the limit cause motors to brake?
If I understand it correctly, it bricks your vesc.
depends… which motors, which vescs you have and which voltage you drive on?
also, did you set the erpm limit to 60 000 while setting up your vesc or is the value on default?
aaalso, did you use bldc tool or vesc tool to set up your vesc up?
the bldc tool has the “limit max erpm with negative torque” field. if it´s activated than it might be the cause.
if you use the vesc tool than it should just lower your torque down the closer you come to the erpm limit you set.
if you used vesc tool but a combination of hw4.12 vesc plus high kV motors and 12s without to change the erpm limit while set up your vesc than your vesc should now be fried.
I have had what I think is the same problem then @iamgeekusa. It would be extremely helpfully if I know what happened so I can fix it as I broke my collar bone due to the incident.
I have a 190kv Motor from Tourque boards AKA diyelectricskateboard I also have there VESC. I set the erpm in VESC tool on FOC I set mine to 60,000 ermp. there was no button for Negative touque. Powering all this is 2x 5s in series (36V)
Any help is Muchly appreciated
Hope you get well soon!
What exactly happened? The board cut out or was braking or just lost acceleration?
Your vesc still working or did the drv pop?
Do you use a bms as discharge? Which remote you use? There multiple reasons why a cut out can happen, doesn’t need to come from the vesc, that’s why I ask.
I was throttling up and was getting pretty fast then the board just stopped and I got chucked off. my VESC is still working. I didn’t have a BMS at the time but I have installed one now.
This is my remote:
I have an inkling that it is the erpm or something with my electronics but a few days after my accident I went back to the Crash site and there were some rocks. I do have 100mm all terrain wheels. Just thinking it could be something else.