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BQ78350-R1: BQ78350-R1

Shachar Armon
Prodigy 80 points
Part Number: BQ78350-R1
Other Parts Discussed in Thread: BQ78350

Hi,

We would like to config our BMS (Li -ion, 7S1P, 4900mAh@25.2V) to support voltage base shutdown:

- Shutdown Voltage set to 2700mV

- Shutdown Time set to 20s

- PF Shutdown Voltage - 1750mV

- PF Shutdown Time- 10s

- Charger Present Threshold- 2000mV

The CUV:

- Threshold- 2500mV

- Delay- 2s

- Recovery- 2750mV

Do you see any conflict between the battery base shutdown voltage level and the CUV Threshold?

BR

  • 0
    TI__Guru* 77283 points

    Hi BR,

    When the BQ78350 device is in Shutdown, it is completely powered off. So if the device shuts down at 2700mV, the protection FETs will be disabled. Then the 2500mV CUV voltage level is meaningless in this case.

    Normally, the Shutdown voltage should be set much lower than the CUV voltage.

    Best regards,

    Matt

  • 0 in reply to Matt Sunna
    Prodigy 80 points

    Hi Matt,

    What if we would like application wise to enter the battery to Shutdown with communication command?

    This sometimes can be even at higher voltage level, say 3000mV?

    BR

    Shachar 

  • 0 in reply to Shachar Armon
    TI__Guru* 77283 points

    Hi Shachar,

    Yes, you can enter Shutdown mode any time by using the command. To wake the device again, you need to apply a rising edge to the TS1 pin of the BQ769x0 monitor. When the device is in Shutdown, both protection FETs are disabled, so no charge or discharge current can flow.

    Regards,

    Matt

  • 0 in reply to Matt Sunna
    Prodigy 80 points

    Dear Matt,

    Good and clear, according to my understanding the shutdown mode is one state with 3 option to enter (communication command, time base- shipping mode or voltage base) and 1 way to recover/ exit the stage- apply rising edge to TS1 pin...in our case (BMS layout) is connect the charger.

    So, if no charge or discharge is needed under this state, no issue or any problem to stay with the CUV threshold - 2500mv (according the cell specification)

    Right?

    BR

    Shachar 

  • 0 in reply to Shachar Armon
    TI__Guru* 77283 points

    That should be fine. Just understand that this CUV protection will likely never trigger if the device goes into Shutdown before the CUV voltage is reached. 

  • 0 in reply to Matt Sunna
    Prodigy 80 points

    Dear Matt,

    Please see our battery pack manufacturer additional questions/ concerns 

    1. Further to TI engineer comments in the other email the day before, the “Shutdown” mode must be set lower than CUV, the same as we have recommended in spec.

     

    1. Whereas, TI engineer did NOT inform whether this shutdown refers to:
    2. a) Charging MOS cut off

     

    1. b) Discharging MOS cut off

     

    1. c) Charging and discharging MOS cut off synchronically.

     

    Please check with TI engineer once again to assure any of the three situations above, which is actually an IMPORTANT issue for us to address. In case shutdown refers to charging MOS only, then there shall be over-discharge occurrence and damage on battery MOS & pre-charge circuit.

    BR

    Shachar

     

    1. If customer persists 2.7V for battery shutdown level, then we must adjust CUV and pre-charge recovery Voltage as already cited in our spec, otherwise we should adjust shutdown Voltage lower than 2.5V while with all other parameters remaining unchanged.
  • 0 in reply to Shachar Armon
    TI__Guru* 77283 points

    Hi Shachar,

    Shutdown mode completely powers down the BQ78350 device and puts the BQ769x0 device into SHIP mode - both FETs will be disabled of course.

    Matt