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BQ24040: Charging Issues on BQ24040

TI-CSC
Genius 12885 points
Part Number: BQ24040

Dera TI Experts,

I am using the BQ24040 to charge 400mah lipo batteries. You can see my settings in the attachments.

sn_customerservice_case_eb3b433f1ba3a4d0602cf715464bcb02_attachments.zip

I am charging the battery at 0.5C (peak) and it takes more than 6 hours to charge. I noticed that after 3h it stays at 15mA for hours ...

My doubts:

1) what is happening? this is normal?

2) Is my configuration correct?

3) What current setting do you recommend I use for a 400mAh lipo battery?

4) I am using a 115 ohm resistor for the LED. Is this too low?

Thank you in advance.

Regards,

Jonard Rico

  • 0
    TI__Mastermind 19195 points

    Hello Jonard,

    The bq24040 will terminate charge based on current delivered to the OUT pin. If the load on the battery is too high it can prevent charge from terminating, in your case the LED is causing a high load on the battery during charge.

    Thanks,

    Nick

  • 0 in reply to Nick Brylski
    TI__Genius 12885 points

    Thank you for your response Nick, below are follow-ups to the initial inquiry.

    1.) Based on the attached schematic, any recommended solutions on how to at least minimize this effect?
    2.) Is my configuration correct?
    3.) What current setting do you recommend I use for a 400mAh lipo battery?
    4.) I am using a 115-ohm resistor for the LED. Is this too low?

    Regards,

    Jonard Rico

  • 0 in reply to TI-CSC
    TI__Mastermind 19195 points

    Hello Jonard,

    I would try raising the LED resistance to at least the 1k range and you should see better results. Besides that your schematic looks ok. For charging current spec you should check with your battery manufacturer usually the max charge would be 1C.

    Best regards,

    Nick