I agree that a ramping time isn’t desirable for me anyway. A default of 0ms would be awesome if it’s implemented. 
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Thanks. At worst, with a default of 0ms as @b264 suggests, it gives us one more tuning parameter.
I am replacing my battery pack with something more capable though.
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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.
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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.
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How much of a difference does MTPA make for the more typical surface magnet motors when they are not at field weakening speeds?
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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.
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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.
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E.g. what would the Cutoff Start and End values be for a pack made out of ANR26650M1A or B? Answer, it’s not that easy, how much Amp are we drawing?
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I would still use 2.875V and 2.750V per cell for start and end. The further you pull the trigger in, the more it will throttle your power
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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?
These settings would still have put me on my arse a week ago, because normally my Voltage sag only went to 57.5V, but on the day it went to 53.5V.
I don’t think it would have. I feel like it would have simply stopped allowing the power to be increased before it got that low.
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My experience begs to differ. Do you know what a total power cut feels like at 40mph?
My cutoff settings were 2.9V and 2.75V per cell. Voltage sag literally went from 57.9V to 53.5V within less than one second.
So right into a full power cut in 0.8s. There was zero time to react or adjust my stance.
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…
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I’m building a better battery.
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Fair enough
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It might, but giving me more time to react is precious for not streetfacing.
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This is also exactly why I prefer one radio receiver per motor. Reaction time is precious.
If one motor loses signal 50ms before the other one, that can be the difference between streetface or not.
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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.
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I’ve been trying to use larger EV motors with VESCs to no avail. I’d love to be able to provide data as I know that some vesc projects have turned up for EV use. Unfortunately I am unsure of how my testing setup needs to change to accommodate these larger motors but I would appreciate any features that are targeted towards this market as it is obviously a target for Benjamin. Anyone with guidance on this issue would be great
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