I have experienced what looks to me like a BQ78350 bug: an ASCD / ASCDL loop without any load connected.
The pack(15S4P) was discharging on a 300W constant power electronic load.
Near the end of discharge, protections tripped 3 times for about 1 second.
The pack would discharge again for about 6-8 seconds before the next event.
I suspect a repeated cell undervoltage.
At the fourth trip, discharging never resumed.
Plugging EV2300 to the pack, I could see ASCDL and ASCD flags were set.
Short-circuit tripping is definitely possible. When resuming discharge on a constant power load, a current spike can occur and be seen like a SCD (settings are delay=70us and threshold~15A).
However, with the load removed, ASCDL and ASCD flags would never clear.
ASCDL should have reset after 15s but did not, most probably because ASCD was set and never cleared.
Increasing ASCD latch limit from 0 to 1 followed by a reset command lead to a set-clear flag loop. ASCD would clear, then ASCDL but ASCD was set again along with ASCDL shortly after. Clear-set-clear-set...
From a multimeter standpoint, DSG FET was never activated.
There was no load connected.
A shutdown and reboot brought back the pack to a proper behavior. I can discharge it again.
I fully discharged the pack that way a few time, except that I have changed for more powerful cells since the last time I did it.
It is the first time that I experience that fault loop.
I could not find any way to break the loop except full shutdown.
This is not an acceptable workaround for a pack in the field...
Any thoughts on that?
Regards,
Frederic
↧
BQ78350 ASCD/ASCDL faults loop even after load removal
↧