Kind of how I originally set up. I up the amps till I see no difference in performance and then back them off until it affects the torque. I have to be old school because I don’t run sensors or telemetry. Never have and you can’t teach an old dog new tricks. Prolonged hill climbs and lots of hard acceleration and braking and get touchy feely with them.
So much of this is where and how you ride too and I can comfortably run sk3 192’s at 100 amps in my environment but I give myself some headroom and run most at 80. Only my evo runs 100 because evo.
I never exceed the max stated or proven amp rating on batteries though and I have blown up too much shit to ever be convinced you can.
It’s stator saturation that sets the limit.
The other factor is heat.
Saturation:
Test: full acceleration from stand still with more conservative amp settings (as suggested by VESC-Tool). No cogging means everything is fine, the motor resistance value is within the acceptable 5% precision tolerance. If cogging happens, you need to lower the motor resistance by 5% for the cogging motor.
Reason: The resistance wasn’t measured correctly, so we correct it manually.
The resistance needs to be set ±5% accurate!
Finally we go higher in Amps and find the spot where cogging starts. Now you saturate the stator.
Heat:
Hot motors have a higher resistance and ultimately they are out of the 5% tolerance for the originally measured resistance. That’s where unexpected behaviour starts. Blocking motors could be the result. It’s not only melting glue or winding insulation being a risk. The motor can’t be commutated properly if it is operates beyond a certain heat and in consequence motor resistance.
What do we try to achieve: operation of the motor within a certain temperature spread.
A couple of things can be done to prevent heat:
a) more gearing and using higher KV motor in consequence
b) dual drive
c) use less average amps
d) use bigger motors
I’ll have less cogging the higher I put motor amps instead of the opposite
I imagine as the winding is gets hotter and increasing resistance and inductance it is loosing synch w the esc and getting more inefficient even before were to hit a point of failure to synch at all
In that case you have something wrong. Your motor resistance is not measured correctly (it is to low).
Once you start to push more Amps, the motor gets hotter and the the resistance value is more in linen with the real resistance. In consequence your motor starts run better when it gets hotter.
However, you should up the resistance value in your case. Try a 5% higher value.
Again, same test: Full acceleration from stand still with cold motor.
No cogging: You got things right.
Cogging: You need to adjust a bit. ± 5%
Hub motors have a severe temperature spread related resistance issue and you might need to work with temperature compensation to resolve matters. The problem about that: It works different for different motors, so there is no general rule of thumb setting. Benjamin switched it off as standard for given reason. It is always better to operate the motor within a certain temp spread, rather than try to patch things up. However, skate hub motors are very problematic and you need to consider many things and compensate many downsides that this design brings on the table.
Heat is also not good for the bearings, the axle shafts, magnets, glue, sensor PCBs etc.
So best practice is to avoid heat all together and cut back power sooner than later.
Sorry to bring this back from the dead. Trying to understand the motor max topic.
If the motors are able to take 60a without overheating and no cogging, but the battery is a low output pack…Do i need to lower the motor max value? Or it doesn’t matter?
