I think you are suggesting implementing a ramping time on the motor current cutoff, there is no guarantee this would be any better. During a rapid voltage sag there’s a good chance power will cutoff anyways, especially if you are going at speed. When something sags like this even when cutting amperage chances are if you continue to try and draw amps it will sag even more dramatically.
I don’t really see this as a problem with the code base but a problem with the power source if it is dipping erratically. I will discuss with vedder the pros and con of adding a brief ramping time to these cutoffs.
I don’t feel like this is the correct solution as the current implementation works fine if the voltage limits are set up correctly. As @Deodand said, If you ignore these voltage limits even for a few seconds at the end of a pack you can quickly sag the cells well below the safe limits, potentially causing damage or brownout.
Maybe a better solution would be a warning in the vesc tool if the battery limits are set to close together, which is based on a percentage of the cell count.
On the surface that sounds fine, but by nature LiFePO4 limits are close together, and they’re more resilient to abuse, so I’d still like to see something like this.
It’s a tuning option, doesn’t mean you need to use it, but for some of us it would be helpful.
This is true, my LiFePO4 packs go and go and go and go and then WHAM they are dead
at these cutoffs
Nothing like li-ion. Bit still you could in theory raise the cutoff start to a level that partially minimizes that, but you’d have to figure out exactly where that exact point would be, and the discharge curve on LiFePO4 is so flat that it still wouldn’t be quite like li-ion.
The discharge curve also changes with the amount of current you draw (voltage sag), so it’s a bit like pin the tail, but the donkey ran off into the desert.
So then you’d literally never be able to use the full discharge capability without having a big P pack, and what about cold mornings when they sag more?
No, because I build for transportation, reliability, and safety. That’s never even possible, by design.
I know what a full-throttle 27mph (43.4km/h) power cut feels like — it feels like you slammed the brakes and turned into Superman.
But regarding the cutoffs, I’m not sure why it’s even allowing your voltage to fall that low, and adding a ramping time would seem to exacerbate that problem in my mind.
I’d suggest using a lower power setting… your problems will evaporate…
IM very HO about the MTPA, field weakening isn’t great for e-sk8 and tiny motors, on big motors like e-bikes we can compensate the extra heat generated by cooling directly the motors. On tiny motors it will most probably just heat up & run less efficient, then lose torque thus speed after heating too much.
With a lighter load or bigger motor this could be a thing, but we’re already pushing these tiny motors to their limits there. We can’t even attach proper fins or try stuff like liquid cooling / statorade / mineral oil. Internal thermal patch and limited airflow is the only thing left, and we’re fighting with little fans the size of 50 to 80mm diameter, at best.
I can see benefits for other domains of use since Ben has tailored his work for many uses an not just esk8 or scooters. But for us the benefit of MTPA is null I believe.
Feel free to demonstrate me wrong on the road. Or off road.
