Strange behaviour on Regen mode

General topics and discussions about the VESC and its development.
kitewinder
Posts: 17
Joined: 29 May 2017, 20:47
Location: Bordeaux

Strange behaviour on Regen mode

Postby kitewinder » 25 Sep 2017, 19:18

Hi all, I'm using the VESC in regen mode mainly on a windmill application
The Vesc is controlled by an arduino . the cards communicate through UART.
As I'm regenerated power by sending braking instruction to the VESC, the UART will stop working after says 60 seconds, motor going freerun and then the VESC restart after 5 s with initialising leds ( Blue and Red ) .

If I don't regen, the problem never appears...

It seems I'm reaching some electronic protection and the cards is shortly shut down and I can't figure this out.

I know it is a very uncommon use of the VESC so that mainly nobody as had this configuration before but if anyone has an idea about where this problem could come from, then I'm really interested !

Olivier

linsus
Posts: 35
Joined: 24 Apr 2016, 10:20

Re: Strange behaviour on Regen mode

Postby linsus » 26 Sep 2017, 09:20

Not sure about the restart. How do you supply power the VESC?

Sounds like you're hitting a voltage threshold(what are your BLDC-tool setting there?), what are you generating electricity towards? A battery?

Current limits might also be applicable.

kitewinder
Posts: 17
Joined: 29 May 2017, 20:47
Location: Bordeaux

Re: Strange behaviour on Regen mode

Postby kitewinder » 26 Sep 2017, 10:26

the vesc is powered with a 54 Volts li-ion battery, 13S

BLDC setting : Vmax : 54.6
Vmin = 8V
batt cut of start 10V
batt cut off end 8 V

I monitor the state of the battery so that I always know the charge level of the battery
The Vesc Regen the battery and in the mean time I'm extracting power from the battery to charge my laptop

Thing is the VESC restart does not happen when on another test bench ( with another vesc but same setting)
5V stay OK, 54 V OK all along the failure phase, I don't think it come from my wiring

The Vesc just shut down it com port for 3 secondes and then restart

ThierryGTLTS
Posts: 86
Joined: 09 Aug 2017, 11:10

Re: Strange behaviour on Regen mode

Postby ThierryGTLTS » 26 Sep 2017, 10:55

You are above the limits of the VESC, 12S max rated.

When using Regen, the voltage coming from the windmill (or other source) is higher than the voltage of the batteries.

13x 4.2V is 54.6V too close to the 60V of the Vdss max of the mosfets and the DRV.

If you can have trials at 12S, I think it'll be motre secure.

Have a Nice Day.

Thierry

pf26
Posts: 304
Joined: 28 Mar 2016, 14:37
Location: FR Valence

Re: Strange behaviour on Regen mode

Postby pf26 » 26 Sep 2017, 11:37

You may want to have a look at the recorded faults in the VESC, causing it to halt. After a fault, use BLDC-tools and in the terminal window, type faults.

kitewinder
Posts: 17
Joined: 29 May 2017, 20:47
Location: Bordeaux

Re: Strange behaviour on Regen mode

Postby kitewinder » 27 Sep 2017, 20:36

that is definitely not an overvoltage problem, the vesc is ok with 13S. As I said, I test this setup on another test bench for hours without problem.

I test your solution PF26, problem is , defaults are cleared when the card is powered down. you can test, it will say : no fault since startup
As the problem restart the VESC, the defaults are cleared. then I can not know the defaults !
Is there a way to read the defaults using Jtag probe for example ?

So cool to have this forum and open source hardware !

pf26
Posts: 304
Joined: 28 Mar 2016, 14:37
Location: FR Valence

Re: Strange behaviour on Regen mode

Postby pf26 » 28 Sep 2017, 06:36

If you power down the VESC, sure it will clear its faults.
But if you keep it powered, even if it flahes 3 times to tell it had an error and needs restarting, then it should keep its faults in memory.
If you kept it powered by the battery and have seen no faults, then I suspect your battery BMS detected an overvoltage and briefly disconnected the battery - still strange, since the VESC capacitors should keep it powered a little while, most likely until the BMS reconnects.
If you can't read no fault, then you should scope the VESC input voltage to try and see if it briefly goes down.

linsus
Posts: 35
Joined: 24 Apr 2016, 10:20

Re: Strange behaviour on Regen mode

Postby linsus » 28 Sep 2017, 10:41

I trust your tests, but personally I wouldnt be confident in my VESC setup running even 12S with the numerous posts of problems past 10S. Just yesturday I read a post in a different forum of a maytech VESC blowing up at 12S in idle. Just my two cents.

kitewinder
Posts: 17
Joined: 29 May 2017, 20:47
Location: Bordeaux

Re: Strange behaviour on Regen mode

Postby kitewinder » 29 Sep 2017, 20:37

Hi all,
We run numerous tests. I am still not sure because the failure seems a bit random. Linsus, it seems you might me right about over voltage.
Does anyone knows if there is a hardware protection for over-voltage that can switch the VESC off ?
Of course there is the soft protection but it seems there also is a hardware protection that switch the ESC off...
For infos, we use maytech VESC with 13S. Our solution will be to limit the voltage by software to 51 Volts which is around max 12S battery voltage.

And for those wondering what happen if you reach the software upper voltage limit ( I have seen this question many time ) the answer is : the motor go free run , brake is released and any commands send to the vesc ( uart nunchuck or whatever ) are not taken into account.

I will go deeper on investigating this failure ans let you know

Olivier

linsus
Posts: 35
Joined: 24 Apr 2016, 10:20

Re: Strange behaviour on Regen mode

Postby linsus » 03 Oct 2017, 09:35

Not familiar with a hardware failsafe. The overvoltage threshold is software based from what I know.
However, there should be a DRV fault present(if it survives at 12-13s), meaning red flashes from the leds before everything dies. I'm not a certain if the DRV faults are 100% tied to the thresholds manually input into the BLDC-tool or if there is a fixed voltage vaule in the code.

You should be able to identify this by typing "faults" in the BLDC terminal which will post the fault log, if there is one.


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