• State Resolved
  • Locked Locked
  • Replies 1 reply
  • Subscribers 63 subscribers
  • Views 405 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.

Original question:

BQ25798: Unexpected behaviour in MPPT mode

BQ25798: Standalone implementation

Robert Trepp
Prodigy 30 points
Part Number: BQ25798

I am currently evaluating this chip for use with a 6V 10W solar panel, charging a 2S Lipo setup. Ultimately it will be interfaced with a MCU and i2C functionality to be fully utilised, particularly the MPPT feature.

However as a fallback I want the device to be able to operate standalone. I am using the EVM kit and 2400 interface to see the register settings etc.

I have however noticed, a particular situation, similar to a previous poster regarding slowly rising input voltages, that when the panel is covered and slowly uncovered, emulating a day night cycle the system gets stuck in Hi-Z mode and will not commence charging. If however the solar panel is disconnected and the reconnected it does commence charging. 

Can you please advise whether with the defaulted register settings the system is suitable for such a situation and if so what prerequisites need to be observed?

Thanks Robert

  • +1
    TI__Mastermind 40325 points

    Dear Robert,

    Upon POR, the device does not have MPPT enabled. In addition, MPPT can only be enabled when the battery voltage is above VSYSMIN.

    To power up from darkness, the part will enter Poor Source Qualification if the solar panel cannot supply enough current. Poor Source Qualification will be run every 7 minutes until the adapter is removed or the source is qualified.

    Running the charger in the sunset condition will depend on if you have MPPT enabled or not. If MPPT is not enabled, once the input voltage drops below the VINDPM threshold the charger will stop until the VINDPM is updated below the current input voltage.

    If MPPT is enabled, after the input falls below the VINDPM it will remain there until the next measurement of the input. The default interval between two open circuit measurements of the input is 2 mins, but if it is set to 30 min and the input drops within the first minute, you will have to wait for the timer to expire to reset the VINDPM.

    Thanks,

    Mike Emanuel

    Please click "Resolved" if this answered your question.