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BQ24070: Is not fast charging

Halil Sen
Prodigy 10 points
Part Number: BQ24070

I built the circuit you see in the schematic

 

Input is 5.25V using the power supply, output voltage is 4.15 V and connected to another PCB I designed. Vbat is 4.05 V . 

When I connect a Li-Ion battery to this circuit, I see that 2 mA current is drawn from the power supply. I can't see any current from ''jumper shorting'' when I try to measure Iout and Ibat. 

I'm using SERTEC 3200mAh 3.7V 180409 Battery. 

All LEDs are ON when I connect the battery. (LED1: Charge / LED2: Charge Done / LED3: Power Good)

The R6 and R8 you see in the schematic are not fitted. 

What is wrong with this circuit? Why is the battery charging so slowly? 

I can add if there is any information I forgot to mention.

Thanks. 

  • 0
    TI__Mastermind 20260 points

    Hi Halil,

    We are looking into this. One of our team member will provide feedback tomorrow. Thanks.

    Regards,

    Jing

  • 0 in reply to Jing Zou
    Prodigy 10 points

    Hi Jing,

    Thanks for reply.

    I soldered new PCB. I think the circuit is working correctly now, and I can measure 1 A charge current for ''< 4V'' battery voltage.

    When the battery voltage rises above 4V, the charging current decreases. (Approximately 0.7A for 4.16V battery voltage)

    But this time I didn't solder the diode rectifier circuit for input power which I did not share in the main topic.

    I want to supply the input power with a BLDC motor. 

    Why didn't it work when I soldered this diode circuit and powered the system from the power supply? Will it work correctly when I connect a BLDC motor, what do you think about that?

    Do you think the only problem was with the diode circuit?

    Best regards,

  • 0 in reply to Halil Sen
    TI__Mastermind 23340 points

    Hi Halil,

    I'm not too familiar with using a BLDC motor as a generator. Do you perhaps have a waveform at the VIN that you can show for just the diode circuit? From my experience with a 3 phase motor, the VIN node would sum of half rectified voltages that are out of phase. Do you have an idea of current output when using the generator? 

    Halil Sen said:
    Why didn't it work when I soldered this diode circuit and powered the system from the power supply?

    Would you be able to describe more of the behavior when VIN was applied with the diode circuit? From what I see, I don't expect a concern after the C9 capacitor charges.

    Halil Sen said:
    Do you think the only problem was with the diode circuit?

    I need a better understanding of the capabilities of the generator input and how the diodes are intended to be used. 

    Halil Sen said:
    Input is 5.25V using the power supply, output voltage is 4.15 V and connected to another PCB I designed. Vbat is 4.05 V . 

    If VBAT is already at 4.05V, the device is charging in CV. With the output voltage at 4.15, it looks like your power supply could be operating close to its current limit. Do you have information on the current output capabilities when you are seeing low current at VBAT = 4.05v?

    Best Regards,

    Anthony Pham