VESC throws erroneous (?) UNDER_VOLTAGE - how to identify the cause?

[braunschweiger]

Hi,
my MAKER_X mini foc plus (HW60, v605) driving small akm-75sx geared hub motor threw an under-voltage error which I think is a malfunction.
10S battery was fully charged, at about 4 minutes into the ride the under-voltage error was given and preveiled. After the initial under_voltage situation, the battery voltage remains fluctuating at very low levels in the below 30V range. A manual power cycle few minutes later brought the system back to normal, voltage was back to about 40V and running normally for another 40 minutes.

It is probably not the battery as same spurious effect has happened previously with another battery (no logs).

I have no idea how to narrow this down further - any clues from the log file maybe (gps coordinates zeroed for privacy)?
Thank you kindly

 

[pwd]

I've taken a look at your log file and I suspect that there is a poor connection to the battery main somewhere or the BMS is shutting down for another reason (are you using a BMS you can monitor)?

 

[braunschweiger]

thanks for looking into this.
No BMS here to monitor. I could rig one up but it would ride piggyback on the battery. As these events are somewhat rare, I might have to carry this taped combo for several rides with nothing happening.

The batteries both are 10S1P. I could understand if a poor connection caused intermittent complete power losses but such long persisting voltage sags is new to me. Anyway, it is something to investigate