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bq20z80 shutdown command

alan56560
Prodigy 100 points
Other Parts Discussed in Thread: BQ20Z80, BQ29312

Hello,

If I put a bq20z80 battery pack into shutdown mode via mfg access command 0x10, are there any cases where the charge & discharge FETs would be turned off when the device wakes back up?

 

To put into shutdown mode, I'll do the following:

1. Unseal battery

2. Turn OFF FETs by writing 0x0000 to address 0x46

3. Send shutdown command 0x10 to mfg access

 

This is a bq20z80 pack w/ bq29312 AFE. I've verified the above works and when the pack comes back up, the CHG and DSG FETs are on as desired. Just wondering if there are any conditions that would cause the FETs to not turn on when the device comes out of shutdown mode. E.g., if there's a long enough wait between steps 2 and 3, etc.

 

Much thanks.

  • 0
    TI__Genius 10225 points

    It is possible that one or both FETs could be off after coming out of shutdown mode:

    1) If the voltage of the pack is too low, the DSG FET will be off until the pack has been charged to a high enough level.

    2) A permanent failure may occur, which would force the FETs off and blow a fuse.

    3) The secondary protector could be tripped by a high cell voltage and blow the fuse.

     

    Step 1) would be the most common. Steps 2) and 3) would only occur if there was a problem with the pack.