VESC FAQ | Regen Braking Configuration BLDC tool & Brake Force

If you didn’t already know the VESC has built-in regenerative braking it can charge your battery when braking.

I also thought It would be appropriate to explain exactly what that is & how regen braking works, Then I realised I actually don’t fully understand the technical principles of how it actually works, Maybe Someone else can explain in detail how the Back EMF is used as a brake force, how it is created & controlled.

Anyway, This is my simple explanation as I understand it: The ESC stops outputting power from the battery into the motor, Instead the motor now turns from momentum as it rolls along the ground, it basically turns into a little generator. It starts generating its own current, known as Back EMF (back electromotive force) which is sent back into the battery just like a battery charger does.

For some interesting analysis on how much this technology can actually charge your battery read this article written by Justin from Grin Technologies.


So now to the actual purpose of this thread

In this thread I will explain how to set up Regen in the BLDC tool. How to configure the brake to make it perform the way you want it, Stronger or Softer braking force. More charge current less charge current.

Open the BLDC tool / Motor Configuration TAB / Motor TAB

These are the two parameters you need to change to make changes to the regen. “Motor Min (regen)” & "Batt min (regen)"

Displayed above is the default settings, these settings work great! The brake force feels really nice, it’s strong but not too strong so you get launched from the esk8.

One thing that confused me a little was the negative values & the wording of the parameters, specifically the “min” part.

For instance if you are using the SPACE Cell and want to maximise the lifespan of the battery and only charge within manufacturer’s rated max charge current of 4000ma (per cell) you may want to have a max charging current of just 12 amps (the space cell is 10S3P. 3 parallel groups X 4a Max Charge Current = 12A Charge current). So you would change the “Batt min (regen)” to -12

Motor min (regen) this is how much current you want inside the motor when using regen braking. If your motor has a rating from the manufacturer saying is is good for 40 amps you should then set this parameter to -40.

So how do these two parameters work together to control the feeling of the brake, the real life braking force you will feel when riding?

As I said before the default settings are great as they are, progressive controlled braking force that brings you to stop in a safe manner. But if you do change the parameters to meet manufacturer’s guidelines what happens?

Batt min (regen): If lowered, say to -12 from the default of -20 will reduce the force of the brake (most noticeable at higher speed). If increased above -20 will strengthen the brake force (most noticeable at high speed). Also it will charge your battery more.

Motor min (regen): if lowered from the default of -60 will reduce the force of the brake (at low speed brake force will not be changed much) if increased greater than -60 you get stronger brake force, also you might get much hotter motor if you do lots of braking at high speed.

Hopefully now you have a better understanding of how the brake settings work in the VESC and you can tune it to suit your electronics and your riding style.

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If I understand you correclty it would work like this for my batteries: I have 3x4S 5000mAh 20C So I should be able to put 20x5 = 100Amps --> -100 in batterie min (charge) For my motor I have Torque’s 2x 5065 170KV 2200W but I can’t find any specs for them in terms of Amps.

20C is your discharge rate.

Most lipo’s however should be charged at 1C

If you have a 10000mah lipo you can charge safely at 10AH.

Some people say you can charge at 2C without damaging lipo.

They are rated to charge at 2C and are 3x 4S 5000mAh so it’s only -10? Are you sure about that, it looks odd.

what configuration is the battery?

you have 3 in series or 3 in parallel?

3 x 4S 5000mAh 20C Tunigy in Series

When the battery is recharging, does that count towards the battery’s cycle limit? In other words, will the life of the battery be reduced from frequent regeneration?

Yes, since it’s the recharging in and of itself that cause the wear on the batterylife. It’s just that it is the motor that provides the charging current instead of the wall-charger.

Sorry for gravedigging :slight_smile:

If i understand this thread correctly, the only way to generate current to charge the battery is while breaking. This means, pushing the board in neutral mode doesn´t even charge the battery a bit, even if i do this for 10 km. So the only way to charge the battery on the road is to push very hard while braking with the remote or roll down a very long and steep hill breaking?

What if your using dual Vesc’s? Would you devide the current and set each Vesc at -6 amps battery regen max?

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if i recall correctly it is not recommended that you push your board with out using the motor since it will fried a componenet in your vesc, i know i read it somewhere here

If the batteries aren’t connected

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The discussion was whether or not your VESC/ESC will be damaged by riding with the board off due to the small amount of electricity created from the spinning motors. We never conclusively found out if it is/isn’t harmful for your system, but agreed that you would be fine as long as the board is on. My personal theory was that the current generated would be minuscule enough to not damage components even when the system is off.

vesc will turn on if connected to motor and they spin. if there are no batteries connected as well to send the energy too it will generate enough current to slam on the brakes if you’re lucky and coasting or ruin components if youre not. think the capacitors. read this on vedders forum and I’ve experienced the brake slam on.

so i guess coasting is regening as well. using the brakes without a battery attached is bad news though and quick death…although I got lucky there too

What if you disconnect the motor wires to push home, say if your battery runs too low. Would it damage the motors to spin if they are disconnected ?

Pretty sure it won’t damage anything, the current has nowhere to go.

I’m pretty sure as long as you have batteries connected and coasting your fine. Assuming they aren’t fully charged and you don’t go down a super steep hill that puts you over the erpm limit

If I have 2x4000 3s batteries in series can I charge at 8 amps?

How does regenerative braking work on a diy board?

whey you apply the brakes the energy of your momentum gets converted back to electrical by the motor, then chemical energy in the battery with roughly 30 percent efficiency. you can adjust on the vesc the amount