Help me understand these Vesc settings

[JesseF]

I am using a 12S battery from Boundmotor, which according to their website has a battery current max of 20A. I need to know these settings so I can ensure my Focbox is programmed properly to run this battery.

How is it that a battery can have a current max lower than the motor current max value? In this case 20A for the battery and 100A for the motors. Perhaps I don’t understand what max current is referring to. In my mind, with these settings the motors would be trying to pull 100A from a battery that can only give 20A. Isn’t that bad?

The motors I want to use have a max current of 30A according to Backfire, and a max braking of 20A.

[Crisfell]

Set motor current max to 30. Set motor current max brake to -30. Everything your seeing now is all default. You need to run detection and set values accordingly.

[JesseF]

yeah I think I have most of it. Just not sure if I’m damaging my battery by trying to draw too many amps or regening too many amps. I have the following settings in my Unity.

so again, in this instance I have the battery max discharge at 20A but the motors at max 27A (I could max out to 30A). I’m not sure why the motor draw of 27A can be higher than the battery output of 20A.

[Johnnylamouette]

@JesseF

not sure if I’m damaging my battery by trying to draw too many amps or regening too many amps

Yes you are, be really carefull with those values, acording to your battery max current draw and max current charge. Seting too high values could unbalance your cells to fast and make your battery dangerous.

@JesseF

why the motor draw of 27A can be higher than the battery output of 20A.

It can be higher in the settings, but anyways, the ESC will limit to the lower value, in this case the battery at 20 amps, in order to preserve it.

[JesseF]

So then what battery settings do you recommend for a 12S3P?

[Johnnylamouette]

What are the specifications of the cells of your pack?

[JesseF]

Presumably they are Panasonic 21700 12S3P: 14.4 Ah (3C) cells and according to how Boundmotor would have you program their VESC, max current for the pack is 20A and max regen is -120A. I have asked Boundmotor to confirm if this is true but haven’t heard from them. Max regen of -120A seems unreasonable given what I’ve seen other people programming their VESC/Focbox. The only information I have about the pack I have boxed in purple this information in the image below.

the battery can be bought here

Electric Skateboard Battery Pack - BOUNDMOTOR

I have the 12S3P 14.4aH version.

Thanks for your help

[onloop]

@JesseF

I am using a 12S battery from Boundmotor, which according to their website has a battery current max of 20A.

This kinda sounds lowish, please share a photo of the label on the battery, or link to the website.

@JesseF

How is it that a battery can have a current max lower than the motor current max value? In this case 20A for the battery and 100A for the motors.

Actually, this is one of the amazing features of VESC based motor controllers!

Even if your battery has a current limit set to 20A, it is actually possible to have a higher current inside the motor, but only when they are spinning at low RPM (duty cycle). This is a great feature because it means you can have very strong torque at low RPM which is important for starting up.

As motor RPM increases closer to its maximum RPM, the current inside the motor will be reduced & be limited/determined by the Max Battery Current Limit that is set.

So rest assured, when Battery MAX current is set up correctly, you can rely on your vesc/focbox to protect your battery.

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Here is a video showing 120 motor amps (I Motor), with battery amps (I Batt) of approx 12amps.

FOCBOX TENKA | Single Motor ESC Running at 120Amps

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@JesseF

The motors I want to use have a max current of 30A according to Backfire

You can probably push this a little bit higher if you wanted to improve the starting performance of the esk8. Could try 40A, Remember, the current will start to get limited by the battery MAX current as your speed increases.

In common uses cases, it’s nearly impossible to run your motors at the maximum current for long periods of time. Especially if they have temperature sensors, as once a certain heat level is reached the current will automatically get reduced by VESC/FOCBOX. But not all motors have temperature sensors!

If you don’t have temp sensors, you must be more careful & monitor the temperatures during a ride. if you are a heavy guy & have many steep hills to ascend you will need to be careful about the max motor current you choose. Too high & your motor will overheat, too low and you won’t be able to climb the hill.

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If you, or anyone else, requires more specific one-on-one help I do offer a paid service.

Electric Skateboard Tech Support

[JesseF]

@onloop

This kinda sounds lowish, please share a photo of the label on the battery, or link to the website.

here it a link to the battery.

12S Electric Skateboard Battery Pack

label

I think I’m cool with the 20A, but what about the regen? According to boundmotor it’s -120A and I have mine set to -20A. I’ve seen many Vescs programmed with -15A

[onloop]

@JesseF

but what about the regen?

Some more details explaining vesc regen.

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 …

-120 doesn’t seem right to me… at this point it seems that bound motor is probably not a reliable source for esk8 technical support…

[JesseF]

update. Bound motor replied to my question with the following:

"here below is our default setting for belt drive and direct drive board. you may need to change the battery current max to lower, just make sure your VESC can handle .

35A for the max current and -60A for the regen makes more sense given how this stock battery performed in my Boundmotor. This should mean my settings of 20A max and -20A regen with my Focbox and backfire hubs are within specs for both the battery and drivetrain…correct?

[onloop]

@JesseF

35A for the max current and -60A for the regen

So they believe this battery is rated to have a higher charging rate than the discharging rate.

That’s the opposite of every other battery and doesn’t make sense. Unless they are using a BMS that limits discharge current. Which might explain the low 35amp rating.

If your battery can only output 35amps max thats unfortunate. 12s3p 21700 should be better.

Battery regen, set that according to the brake performance you desire. Go do some testing, make incrementalchanges!

-30 or -40 might be enough. Maybe less. Kinda depends how much you weigh and several other variables, wheels size, reduction ration, motors.

[JesseF]

yeah see this is why the a forum is perfect for this type of thing. All the information I was accumulating sounded a bit off, and I’m still not up to snuff on the basics. A note on negative integers with regards to regen amps, is -40A less than -20A?

Another way for me to look at it is, if I were to set regen to 0A, then I would be returning 0 amps to the battery during braking, correct?

[Skitzor]

-20a is less than -40a

and if you put it to zero, you basically have no brakes

[onloop]

@JesseF

note on negative integers with regards to regen amps, is -40A less than -20A?

This confused the fuck out of me the first time i was setting a vesc up too.

The lower the number, below zero, the higher regen current. So yes, in VESC. -40 is higher than -20

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For the noobs and for the sake of common logic, I always thought the parameter for changing regen should be written in the GUI simply as “regen current” and then the “current” as a positive number.

Q: How much regen current you want to send to battery? A: I want 20amps

Surely that makes most sense to non-enginner folks, beginners etc? But anyway… once you know how it works it’s not an issue.

[NullBlox]

I was under the impression that the Regen is for high speed braking

( Low Battery MIn values result in weak brakes at speed!)

as well as the - amp settings, well they are a done in a pulse/burst not a direct flow.

So its safe to go above your charge rating due to the pulse charging and maybe should.
In order to have brakes at higher speeds. Just know that setting this too high will make some super snappy brakes at high speeds. Which may result in injury.

source link

@onloop

Q: How much regen current you want to send to battery? A: I want 20amps

Surely that makes most sense to non-enginner folks, beginners etc? But anyway… once you know how it works it’s not an issue.

I just read the Wiki, that in itself is pretty easy. If you read your charger, its prob like 5amps. So if you go by what your saying, people would be lead to believe that 5amps is all they can use for regen current. When in fact they can more than double that and be safe since its a burst and not constant.

Hope this info helps and the source should be trusted since its Vedder himself. Im just passing along what I read.

[onloop]

@NullBlox

So if you go by what your saying, people would be lead to believe that 5amps is all they can use for regen current.

Never thought of it like that… it’s kinda hard to predict what a total-noob is thinking when building tgeir first esk8. Now that you mention this, i can definitely see the logic behind that thought process.

However, i kind of hope/pray/believe that most people are smart enough to look up the battery specifications to determine what it is capable of.

But even that information is somewhat misleading, because, as mentioned, we should choose safe braking settings as a priority over max rated specs of battery cells.

[JesseF]

I’m initially less concerned about braking as I am about silently damaging this battery while testing. Anyone who goes full throttle on a new setup is asking for trouble so the need to dial in the brakes comes second to ensuring the heart of the system is setup properly. The battery specs I posted in my first post seemed odd when compared to other battery setups I’ve seen and the specs the manufacturer has sent me since are different than those posted on their website. It’s good the forum exists with knowledgeable people.

[JesseF]

setting the brakes to 20A is definitely what I want. I will probably bump the motor and battery specs to 30A respectively. Otherwise this has been a fun build. I like the low stance and the backfire hubs coast for ages. I’m not a big fan of the amount of nose and tail projecting past the trucks, so I may trim them up.

[JesseF]

anyone have it where a FOCBOX won’t accept new configurations? I’ve got through the guided setup and it all seems to work fine until I’m asked to hit “apply updated config” and nothing happens. This is how the FOCBOX started out of the box and I contact tech support and while I waited I magically got it working. Now, no luck.