I am running lipos with all currents set either +90 or -90 so I have good brakes all time maybe sometimes too good 
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Yeah, I set mine at -18 or -20 per Vesc on 10s6p. I would go to -8 per VESC on your battery and feel just fine about it. Like many have pointed out, it is only in short bursts, and brakes are niceā¦ even if it does slightly reduce battery life. Worth it.
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Alright, so I set my motor limits to Ā±80A each, and then limited total power per motor to Ā±2500W (so that I donāt go over the specified limits collections/electric-skateboard-motors/products/electric-skateboard-motor-6355-190kv)
What I noticed was that acceleration is even crazier now, but slowing down from top-speed is still very bad. Hereās a video, where Iām going full-throttle, and then start breaking with full-throttle as I go over that speed-bumb:
See all the parked cars I passed? Well, that happened to me the other day in a traffic jam, and let me say ā having to thread the needle between cars with no space to put your foot down to mechanically break is very scary 
Hereās a dump of screenshots from vesc tool, in case someone wants to look into them. (I havenāt messed with anything except the very basics, that get set with the wizzards)
Screenshots
General motor settings:
FOC settings:
You can increase the negative braking current until you are satisfied with it, as I always said, itās better to have the battery last less due to to high braking current then need to brake one day in an emergency and donāt have enough power
Do you have a Bluetooth module ? If so do a full brake from top speed to zero so we can see whatās happening
Just be carefull overcharging Lions can lead to fire 
Always change a small bit and do testing and see how battery handles
Yeah, donāt go to crazy, but if itās almost good you can increase a bit more
But if even with this settings is really weak then thereās is something wrong
The idea is that at top speed because of Duty cycle your reach max voltage and braking is basically by bat min current so at top speed you only allowed to brake with 8A current, at slows speeds because duty is low you can brake a lot more 
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Thatās for regenerative breaking, I was told in this very thread that battery limits shouldnāt affect breaking, since it would just result in heat, and thatās what I expected setting my motor min to -80A would doā¦ 
Speaking of which, is there other VESC firmware available that would be smart enough to raise these current limits when the voltage is low? Iām surprised it doesnāt do that already, as -8A for the battery logically (at least to me) means that when itās breaking at low voltages, it should apply that current limit to the upscaled voltage it uses for charging the battery. I guess Iāll go out and buy a bluetooth module for further testing.
Well thatās for general braking, because of internal resistance of motor you will not have any much braking force so it would be even worse than without regenerative braking. Without load motor (which when braking turns into generator) doesnāt have any load and spins almost freely.
There is no other firmwares as it works for everyone normally Just your battery is too small for this kind of application It would had made more sense going with lipos
EDIT: If you want shorten motor wires and try to spinā¦ thatās how much brake force you will have
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The vesc only do regenerative braking with the exception in really slow speeds that it shorts all phases together, that happens because even at full pwm (95%) it canāt apply the current you want because of the low backEMF generated at low speed
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Set min batery current to -10A per motor (-20A is the max my ESC can handle, and I definitely donāt want to blow that up). Didnāt help really, but I guess itās better than before. Lesson learned then: need to have more cells in parallel/different cell technology for future builds, so that I can break more.
Sidenote: 80A per motor sends me flying off (front of the board lifts up + belt skips) even when holding on with with my hand. Amazing
This is incorrect. All braking is via regen only. (Check the vesc designers explanation over at the vesc tools forum.)
Only 4a goes back as charge to the batteryā¦ Whatās wrong with it?
Manā¦for sure itās all regenerativeā¦how else you wanna get a break force. Sorry if my English is not good enough, but not all of your break energy goes as charge back to your battery thatās what I tried to say there.I have never seen a motor with 100% efficiency.
From the short video you posted + the comments youāve been writing Iām getting the feeling youāre dealing with belt slip here. How tight are your belts? It might be worth putting them tighter to get more grip when braking. I tend to go max speed, and then I hit full brakes, and if the belt doesnāt slip then I increase the regen by 1A until I reach the point where it slips, and I back down again and then leave it there so Iām just at its limit
Itās not belt slipping, that I would feel. (I once nearly fell off in front of a car do to one of my belts slipping ā sent my board to the side instantly
The current breaking limits are manageable, I just need to try really hard to not ride aggressively XD (keeping my distance before cars, slowing down before I need to make a turn, etc.)
I too am not super satisfied with how hard I can brake, especially at high speeds, but as you mentioned I feel the most important thing is to ride safely and preemptively by slowing down a lot way before a turn or dangerous areas
Maytech is selling a R-brake. With that you can have a better braking result.