I think @Venom121212 did some science. The maximum duty cycle the vesc allows will be a few % lower for every 5% you drop that current limit start. WIth a setup of 85% start, 95% end, it only really goes up to like 88% duty cycle even while pinning the throttle down. With a start of 90% and an end of 95%, it gets closer to 95%.
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Both points are valid and correct, but while wind resistance and friction exist, lowering the torque does “at least slightly” lower the top speed, how much is dependent upon many things.
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You also lose brakes above normal top speed, does field weakening alleviate that? That’d be a pretty big bonus as a last resort
Yeah, my understanding of FW is it burns a ton of power and increases the effective Kv of your motor. Whenever you set field weakening to kick in, your duty cycle will increase slower. You’ll stay well below your max duty cycle, and the original duty cycle limits still apply.
edit: To clarify, field weakening does exactly what it says it does, it weakens the magnetic field of the motors. A weaker magnetic field has a similar affect to increasing motor kv
not really i accelerate to 33mph and thats it , i use FW and it will continue to accelerate past 33mph.
to a degree yes, however i have noticed no real watt hour increase, it does cook the shit out of the motor tho
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If you stay below the non-FV loaded speed with FV enabled, does anything change?
i haven’t noticed a difference, the acceleration between the non-FW and FW rpm is noticeable, the torque is close to 1/3 or 1/2 of normal i would say during FW
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Is it a sudden change or does it taper off?
In theory it should taper off, as FW current is applied gradually as it’s needed
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all I do is weaken field on my ebike builds
I think my sur-ron only does 40 without it 
it does taper off but when i hit ~38mph is when i feel it.but i don’t notice when it kicks in
I was using some light field weakening on my efoil and appeared to help boost the top speed on foil a bit, but pretty puckered to going 25mph+ (on 14s pack), so didn’t do a lot of testing. Efoil is a pretty use case for this since on need high current to get on foil, but while on foil you run into duty cycle limit well before current limit.
The situtation it best helps with is this: You set vesc for current control 0-150A so you can get on foil. After you are on foil at 95% duty cycle you are only drawing like 80A max. Lets say that is 60% throttle, without field weakening after 60% throttle nothing happens. You pull the trigger and expect power and don’t get any and it is pretty non-intuitive (and not what you want to happen at high speeds). With the field weakening on you still get some more power if needed and throttle response doesn’t feel bad.
I was meaning to try on a my 12s pack where you hit the duty cycle limit at a lower speed, but hadn’t done that yet… When I was running that pack I would run into that situation way way more.
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Would a better solution be to use a 20S pack?
Even more so if water cooling heatsinks is an option available.
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There is some worry about higher voltage and water and zapping yourself if water got in. I would say most people run 12s, a few on 14s and a couple running 16s.
That makes a lot of sense.
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Reminds me of trump’s rambling about whether he’d rather be on the battery of a sinking electric boat or in the water with sharks. I think the difference in voltage between 12s or 16s is pretty insignificant if it shorts.
Seems a motor that was leaking ( I guess simply not being fully insulated) will produce an ac current through the water and if you also were in contact with some connection to the battery that sounds like the biggest danger. Risk of electric shock - Safety - FOIL.zone
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Yeah I’d go up to 16s, but probably not any higher. I was trying to find the video of a guy that zapped himself testing in a bathtub through AC on the motor on foil.zone due to an issue with isolation but can’t seem to find it right now 
Really only a problem if there is an issue somewhere, cut motor wire, etc. Not too many people have done much experimenting to see at what voltage hurts the most in fresh or salt water! There is a issue with large boats and people drowning to do 120AC leakage from outlets near the water. (Electric Shock Drowning)
But really 14s with 120kv motor goes much faster then most people would go anyways. 12s with field weakening would probably be just as good.
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moving this conversation out of lil foccer thread.
Is there a reason they have adopted it without hesitation, but we pee our pants anytime someone says the words “field weakening” for esk8?
My knee jerk reaction is that we’ve dealt with so much firmware bs that we’re always hesitant to update and try new things. Field weakening is a concept they’re already familiar with as many people suspect that future motion one wheels have it enabled.
Also I am in a bunch of telegram groups where this stuff was developed and tested by vesc contributors and riders. Only think I think doesn’t work RN is field weakening + MTPA, and that’s currently being investigated.
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Now that I think about it, it makes a lot of sense that these vescwheel/floatwheel/EUC people are trying (taking a risk) on field weakening.
We have gearing to push our top speed higher, and they don’t have that option available. If you ride your onewheel at 28mph forever I’d see how you would be pretty desperate to try anything that would give you a speed boost, and field weakening is kind of the only option, other than changing series count, which is a challenge with the one wheel design.
With 20s controllers available, 99% of esk8 folks can get the top speed and torque they want without field weakening.
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