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BQ24650: BQ24650 charge query

Star Xu
Genius 9645 points
Part Number: BQ24650

Hi

The customer design with BQ24650, please refer to the attached schematic.

It can be seen from the figure that there is a diode between the bq24650 output and the battery. The purpose is to prevent the battery from supplying power to the chip in reverse. Will it cause the internal mechanism to fail to detect the battery many times after one night, so it will not be charged.

MPPT is set 1.2V, the input voltage is about 14V. The battery is 2 series of lithium batteries. The terminate voltage is set to about 8.3V.

The charging pad is connected to the solar panel. After a night, when the open circuit voltage of the solar panel is greater than 17V in the morning, the indicator light of the charging panel does not light up.

Measure the battery voltage is 7.5V, but the charging does not start. Re-plug the battery, the indicator light of the charging board will light up, and then measure the output of the solar panel is about 14V, and the battery charging interface is 7.5V.

Please help check it.

Thanks

Star

  • 0
    TI__Genius 9645 points

    Hi

    Add more informations.

    The device's battery pack PIN can only be input because of the added ideal diode. Other functions are currently normal. It will fail to charge when there is no sunlight for a long time.

    The table on the picture is that I used the data acquisition instrument to record the voltage across the acquisition resistor (the record is the change of the charging current during the entire time period). This non-charging phenomenon does not occur 100%, 50% probability, and it is not completely uncharged, the output has a voltage (normal range), and the current is still 6mA.

    The overall function is to provide a charging current of 8.4V 100mA to a device.

    Thanks

    Star

  • 0 in reply to Star Xu
    TI__Mastermind 23450 points

    Hello Star,

    Star Xu said:
    It can be seen from the figure that there is a diode between the bq24650 output and the battery. The purpose is to prevent the battery from supplying power to the chip in reverse. Will it cause the internal mechanism to fail to detect the battery many times after one night, so it will not be charged.

    I recommend looking at this application note for further information:App Note

    Best Regards,

    Christian.

  • 0 in reply to Christian Moyer
    TI__Genius 9645 points

    Hi  Christian

    Thanks for your help.

    According to the note, "The battery detection scheme does not function unless an extra capacitor is placed after the diode” Does it mean that if add the diode

    may cause the battery detection function fail?

    Waiting for your reply.

    Thanks

    Star

  • 0 in reply to Star Xu
    TI__Mastermind 23450 points

    Hello Star,

    Yes it may cause the battery detection to fail. That is why I recommend reviewing the app note to see how to do it correctly.

    Best Regards,

    Christian