• State TI Thinks Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 1 answer
  • Subscribers 63 subscribers
  • Views 396 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

BQ77915EVM-014: BQ77915

iliya stachi
Prodigy 30 points
Part Number: BQ77915EVM-014
Other Parts Discussed in Thread: BQ77915

I have an issue with an BQ77915EVM-014 evaluation boards.

I have 2 evaluation boards, connected serially, balancing 6 cells, 3 cells on each board.

Once I'm charging the batteries each board is balancing "his" 3 cells.
At the moment first balancer finished charging "his" cell, it's closing the charging mosfet, the other balancer cannot continue charging the remain 3 cells, so I have 3 cells fully charged and other 3 charged only partly, 75% approximately.

  • 0
    TI__Guru* 81034 points
    Hi Iliya,

    Are you trying to use BQ77915 in a stacked configuration? The EVMs are not designed to easily test stacking, but it can be done. Did you follow the steps in Section 3.4 of the EVM User Guide? Following these instructions should allow the two devices to work together to control the FETs for the bottom module.

    Matt
  • 0 in reply to Matt Sunna
    Prodigy 30 points

    Thank you.

    Yes, I connect 2 BQ77915EVM-014 boards acc to 3.4 with 3 cells on each EVM board (6 cells on 2 boards).

    As I said: I have a difference between BOTTOM pack and TOP pack. While I see a BOTTOM board banalcing between 3 BOTTOM cells, and TOP board between 3 TOP cells

    Cant see balancing between each other. What I mean is that in the end of charging I have 3 TOP cells (connected to TOP BQ77915EVM-014 board) about : 3.7V each , and 3 BOTTOM cells (conneted to BOTTOM BQ77915EVM-014 board) about 4.2V each.

    A question is: Can 2 stack conneted BQ77915EVM-014 boards balance between cells of each other?

    i.e cell 2 on BOTTOM board with cell 6 on the TOP board, or they balance only cell connected directly to the boards themselfs.

    If yes, How to connect them?

  • 0 in reply to iliya stachi
    TI__Guru* 81034 points
    Hi Iliya,

    Your connections look good. The stacked boards should be able to balance between the cells of each other. One thing that might stop the balancing is if over-voltage is detected on one of the cells - the protection feature would then stop the balancing. I think the cells must have started charging with very different initial voltages? In a typical battery pack, the cell voltages should be much closer at the start of charge, so it would be very unlikely to see an overvoltage on a cell while another cell is still at 3.7V.

    Best regards,
    Matt