BQ40Z50-R3-DEVICE-FW: CHG and DSG FETs Stuck Open - Why?

Eric Castle

Part Number: BQ40Z50-R3-DEVICE-FW

Hello,

I have a battery pack where both the discharge and charge FETs are stuck open, but I don't understand why. I've tried looking at the status in bqStudio (and comparing it to a working pack), but nothing is jumping out at me as the culprit. I don't see any of the obvious protections settings having tripped. I do see that the "FUSE" bit is high, but it's unclear what this means (the manual isn't particularly illuminating). Anyone have any ideas? I included a screenshot below of the display from bqStudio.

Thanks,

-Eric Castle

over 3 years ago

+1 Wyatt Keller over 3 years ago

TI__Guru** 105590 points

Hello Eric,

According to the gauge the FETs should be closed (XCHG and XDSG are 0 and FET_EN = 1) There may either be damage to the gauge or the PCB/FETs.

Sincerely,

Wyatt Keller

0 Eric Castle over 3 years ago in reply to Wyatt Keller

Intellectual 710 points

Thanks. I'd guess damage to the gauge or the PCB/FETs. The pack did go through abuse testing, but I was thinking it unlikely that the gauge would still communicate if damaged.

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BQ40Z50-R3-DEVICE-FW: CHG and DSG FETs Stuck Open - Why?