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Original question:

BQ25798: Unexpected behaviour in MPPT mode

BQ25798: BQ25798 issues

Christoph Dunkel
Prodigy 10 points
Part Number: BQ25798
Other Parts Discussed in Thread: USB2ANY, , BQ24650

Unfortunately my TI Charger GUI V1.4.3 now has some issues which prevents me from proper continue this test.
I got asked to update the Chrome Add-On which I did successfully. I am also able to connect (says Connected in green) and I could start setting it up.
But the data is not synchronized properly. No matter how I set "Auto Read" and "Write Mode".

I now got it charging but the GUI says it is not charging. Other data is also not updating the way it should. Strange.

For the second issue: It was connected to a 9V/ 10W Solar panel. It worked with no issue one full day but then the next day it did not start charging at all. While Vin was >8V (measured). 
After disconnect/ reconnect the panel it started immediately. I guess that is not meant to be this way?

My IC is revision 7 if that matters.

  • 0
    TI__Guru**** 165856 points

    Hi Christoph,

    Did you update the USB2ANY box with the latest firmware at the link below?  That seems to fix most communication issues.

    www.ti.com/.../slvc695

    Does your EVM have a PQ2579X IC or a BQ25798IC?  If PQ2579X, the poor source function may be causing your charger to enter HiZ if the input source is too weak. The host can disable charge, force exit HiZ and then enable MPPT.  The BQ25798 IC has this issue fixed.  

    The BQ25798 MPPT function is not enabled by default and must be enabled via I2C write.  The charger will start up and set its VINDPM level based on the sensed voltage at VBUS during power up.  If the voltage at the next power up is below this value or it drops below this value, and MPPT is not enabled to periodically re-sense the MPP, the charger stops charging. Also, if the battery has discharged below the SYSMIN (MINSYS) voltage, MPPT is auto disabled.  So, I recommend setting MINSYS to the lowest value that will keep your system running.

    One last reminder, if the watchdog is not disabled or the timer bit is not periodically written to via I2C, many registers, including EN_MPPT, get reset.

    Regards,

    Jeff  

  • 0 in reply to Jeff F
    Prodigy 10 points

    Hi Jeff,
    thanks a lot for your feedback!

    USB2ANY fw is the one you posted. Version 2.8.2.

    Indeed, my EVM has PQ2579x. Just saw that now.

    MPPT I enable using I2C. I just wished there would be a IC version which has this enabled as standard. Now I need an MCU just to configure MPPT mode.
    The Watchdog thing I figured out last time while setting it up. Right now I am just not able to configure it natively as the registers are not loaded or written properly anymore.
    Could this be due to the last Chrome USB2ANY driver update?

    Kind regards, Chris

  • 0 in reply to Christoph Dunkel
    TI__Guru**** 165856 points

    Hi Chris,

    Unfortunately, I don't support the USB2ANY.  You might try creating a new post about USB2ANY on the forum.  Have you tried using Firefox instead of Chrome?

    Regarding the IC, we have the BQ24650 with external FETS.  It is standalone and uses external resistors to set a fixed % of the input voltage.  It does periodically sample the input voltage.

    Regards,

    Jeff 

  • 0 in reply to Jeff F
    Prodigy 10 points

    Just tried with chrome so far.
    Will try with Firefox then.

    BQ24650 is unfortunately not what I look for. It supports only a fixed input voltage and is therefore not suitable for different panels as it is not really tracking anything other than the set voltage.
    Also it is just a buck and not a buck-boost configuration.

  • 0 in reply to Christoph Dunkel
    TI__Guru**** 165856 points

    Hi Chris,

    You are correct that BQ24650 is only buck. To clarify about MPP point, it is not a fixed voltage but a fixed percentage of the sensed input voltage.  So, for solar, customers typically set to 80%.

    Regards,

    Jeff