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fault led on bq78PL114 8S EVM cell simulators not balanced

Ronald Deang
Intellectual 260 points
Other Parts Discussed in Thread: BQ78PL114, BQWIZARD

I'm working on a bq78PL114 EVM. I'm simulating cells using resistors as shown in the user guide. Without being hooked up to the board, I see 3.6 V across each "cell." But after hooking them up to the board, the fault LED comes on and the resistors don't have the same voltage across them. Of the six, the first four measure 4.1 V and the last two measure 2.5 V. I saw the warning in section 4.1 about PowerPump currents causing voltage fluctuations. Could this be the problem? What can I do to resolve this?

Thanks,

Ronald Deang

  • 0
    Expert 2135 points

    Do you have the same problem if you turn off balancing? IIRC, it's recommended to do that when using resistors as cell simulators.

  • 0 in reply to John M
    Intellectual 260 points

    How do you turn off cell balancing again? Do you have to do that through BQWizard?

  • 0 in reply to Ronald Deang
    Expert 2135 points

    Yes, you'll need to have the EVM connected to bqWizard in order to turn balancing off.

    It's bit 15 of the Hardware Configuration Register but I don't remember which tab in bqWizqrd has the "Balancing Enabled" or"Balancing Disabled" (forgot how it's named) parameter in it. A few seconds of going through the tabs will bring it up though. It's the bottom parameter in that tab's list.

     

  • 0 in reply to John M
    Intellectual 260 points

    So I tried running the board again to connect to BQWizard, with the same exact set up as I mentioned previously. But now the fault LED won't turn on. So when I tried running BQWizard, it obviously could not find the board. I didn't try running BQWizard with the fault LED on, so I don't know if the SMBus was working then either.

    But with the board not even turning on the fault LED, does this mean the board is damaged? Is there a fuse I can check to see if it's blown?

  • 0 in reply to Ronald Deang
    Expert 2135 points

    No fuses.

    There's really no way for me to tell what's wrong. Did you carefully follow all the set up steps in the EVM User's Guide and confirm all cabling, connections, voltages, etc.? Do the state-of-charge LEDs blink when you apply power to your cell-simulation resistor string? I've forgotten what the powerup LED pattern is, you can check the tech ref manual.