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BQ76940： Instantaneous OV alarm after turning on equalization

Luo XiuFeng
Intellectual 676 points
Part Number: BQ76940

   In the case of charging, I turned on the equalization function of CB6, but the OV protection was instantaneous. The threshold of my OV setting is 4.3V. It can be seen from the PC software that the voltage of the 5th string has reached 4.7v, but I checked with a multimeter and found only 4.2v. How can I solve this problem?

 

 

  • 0
    TI__Guru 54715 points
    Hi XiuFeng,
    It would seem there is a connection problem on the board.
    If it is an EVM used without cells be sure the cell simulator switches are closed, note that the cell balance will alter the voltage across the resistor divider and other cell voltages will change.
    If it is an EVM used with cells be sure the cell simulator is off so the cells do not drain. Check the connection to cell 5 since it seems turning on cell 6 balancing caused the cell 5 terminal to go up and the voltage to report high.
    If it is your own board check connections of VC5, VC5X and VC5B to the cell through the appropriate filter resistors and topology shown in the data sheet or other reference documents.
  • 0 in reply to WM5295
    Intellectual 676 points
    What board do we draw ourselves, what is the unit simulator switch? Where did I find him?
  • 0 in reply to Luo XiuFeng
    TI__Guru 54715 points
    Hi XiuFeng,
    If you have designed your own board for a battery it is unlikely you included simulation resistors. On the EVM they are the resistors shown in Figure 40 of http://www.ti.com/lit/slvu925. The switches are S3 and S4.