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BQ76930EVM: Configuring EVM with a 7s Pack for Evaluation

jasonp
Prodigy 140 points
Part Number: BQ76930EVM
Other Parts Discussed in Thread: BQ78350-R1

I have ordered a BQ76930EVM for evaluation.  I have went through the user guide ( http://www.ti.com/lit/ug/slvu925b/slvu925b.pdf 

  • In Battery Management Studio, the IC and battery icon on the left grey out, and come back every couple of seconds (see image below).
  • When the icons are not grey, I am only able to click the "Refresh" button once, and some data is obtained.

I followed the cell connection table from another document ( http://www.ti.com/lit/ds/symlink/bq76930.pdf ), section 8.1.1 and connected the cell pack to the EVM as shown in the images below:

schematic:

EVM connector block and board:

R1 and R50 are installed on the EVM board (0 ohms).

Is the cell pack connected properly?

Are the jumper settings correct?

Am I missing anything else?

Please give me all possibilities so we don't lose valuable time communicating through the forum.

  • 0
    TI__Guru 54715 points
    Hi Jasonp,
    The connection looks correct. With cells it would be preferred to remove the parallel resistors and connect the unused VCn pins as well as the Cn pins, but that should work OK and not cause the problem you are experiencing.
    The dashboard blinking and communication failing are typically from too fast of a scan rate or the gauge getting busy. If the dashboard goes gray and the communication stops completely the gauge has shut down the system or power is removed.
    In the screen image cell 4 is shown as 44 mV. This is low and the gauge will shut down. You don't mention re-booting the board, but that would be the expectation. Since the connections look right the expected cause would be the AFE Cell Map set incorrectly. To keep the gauge awake apply a simulated charge current as described in the user's guide section 6.4, a few mV on SRP should be sufficient. Default cell map is 0x13, for 7 cells you need 0x0277 (check).
    Of course you might check the wiring at the cells and voltages on the board test points.
  • 0 in reply to WM5295
    Prodigy 140 points
    WM5295, thank you for your quick response.

    Setting the AFE Cell Map to 0x0277 resolved the issue.

    Where is the value setting found for a 7s battery? I must have missed a document or application note.
  • 0 in reply to jasonp
    TI__Guru 54715 points
    Hi Jasonp,
    Setting the cell map is mentioned in the EVM user guide quick start section 2.2.2 step 17, the example is for 10 cells. The AFE Cell Map is described in the bq78350-R1 technical reference manual section 2.6.3.