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BQ24650: MPPSET drifts when set to 1.1V

Michel Fripiat
Prodigy 90 points
Part Number: BQ24650


Hi support team,

We are facing an issue with bq24650 during the charging mode. When MPPSET is set to ~1.1V to charge the battery at the rate of ~16V/5A, the bq24650 drifts the MPPSET to ~1.4V after some time. And battery is charging at lower rate of ~19V/0.31A. See scope traces below.

After the issue occurred, we can't change the charging rate anymore which become problematic to maintain MPPT charge of the battery.


note: Our design uses a digital potentiometer to change MPPSET. a MCU is varying the potentiometer to perform maximum power point tracking.

MPPSET trace:

MPPSET trace

PV trace:


Schematic:
Schem_SL-A208-B_4USB.pdf

  • 0
    TI__Mastermind 41485 points

    Hello,

    Please read Section 8.3.2 of the datasheet. The MPPSET pin will reduce charge current to maintain a 1.2 V voltage. Going up is not inhibiting charge.

    What is your battery voltage when the input current is decreasing? You could be in taper charge requiring less power from the PV panel (which makes sense why the panel voltage went up and panel current went down).

    Thanks,

    Mike Emanuel

    Please click "Resolved" if this answered your question.