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BQ2970: Removable Batteries

Nick Thompson1
Prodigy 30 points
Part Number: BQ2970
Other Parts Discussed in Thread: BQ2980

I need a LiPO BMS chipset that works with removable batteries.

Our application uses 18650 cells that are removed from our device for charging.

Our initial prototype uses the BQ2970DSET, however, this goes into Undervoltage lockout when the battery is removed. 
To unlock the BMS when a new battery is inserted,  V- and VSS need to be momentarily connected or the system needs to be connected to a charger (as per page 17 of the datasheet).    

I understand that most BMS' are designed to be permanently mounted to the cell and that this is a fairly unique situation 

Is there a modification that can be made to the BQ2970DSET circuit that automatically unlocks it when a new battery is inserted?

Or is there another chipset that we should be using?

  • 0
    TI__Expert 7455 points

    Nick,

    When the battery is disconnected, it is necessary to short the V- pin to the VSS pin to wake the chip up from shutdown. 

    It might be helpful to take a look at the BQ2980 High-side protector. It is a similar device, but it includes a CTR pin that can be configured to override the FET driver by host control to create a system reset or shutdown function. The datasheet is attached here:

    http://www.ti.com/lit/ds/symlink/bq2980.pdf

    Hope this helps!