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BQ24296: Not charging Li-Ion Battery Fully

Abigail Leonardi
Expert 3380 points
Part Number: BQ24296
Other Parts Discussed in Thread: TUSB320

Tool/software:

Hi, 

One of my customers is using this device to charge a single cell Li-ion battery (in combination with TUSB320) 

They've programmed the Fast Charge Current limit to a large value (equating to 2.688A) however the batter is only charging to 650mA, do you have any recommendation on resolving this?

  • 0
    TI__Genius 17585 points

    Hi,

    There are a few different factors that could be causing the limitation in charge current. This includes possible TS faults (such as TS Cold), battery voltage (due to Pre-Charge or CV Charge), input current limits, and DPM.

    Can you provide Voltage at VIN, VBAT, VSYS, as well as register values when charging at 650mA?

    Best Regards,

    Juan Ospina

  • 0 in reply to Juan Ospina
    Prodigy 20 points

    Hi Juan,

    I have measured the VIN, VBAT, VSYS when charging at both 386mA and 759mA.

    Charging at 386mA:

    • VIN = 4.89V
    • VBAT = 4.18V
    • VSYS = 4.18V

    Charging at 759mA:

    • VIN = 4.75V
    • VBAT = 4.17V
    • VSYS = 4.19V

    Unfortunetely, I could not read the register values over jig. I will try to get the values and share with you as soon as possible. If you need another information, please feel free to ask.

    Regards,

    Yuichi Kouno

  • 0 in reply to Yuichi Kouno
    Prodigy 20 points

    Hi Juan,

    Updates. The charging current was increased when I attempted from almost empry level. I used the adapter rating 3A at 5V.

    Charging at 1.2A or around 900mA:

    • VIN = 4.34V
    • VBAT = 4.15V
    • VSYS = 4.15V

    The register values are attached. The difference between aorund 700mA and around 1A is just Input DPM mode state.

    Around 1A:

    Around 700mA:

    Please let us know if this results are expected.

  • 0 in reply to Yuichi Kouno
    TI__Genius 17585 points

    Hi,

    386mA and 759 mA Case:

    Without the register values it is difficult to say exactly what is limiting charge current, but because the VBAT is close to the 4.2V battery regulation voltage, I would imagine that it is most likely related to the CV regulation loop reducing current. Raising the battery regulation voltage should cause an increase in charge current, which can be used to confirm this theory.

    1A ICHG Case:

    Based on the configured "Input Voltage Limit" and your VIN voltage of 4.34V, as well as the "Input DPM" status showing as "In DPM Regulation", I believe this is VINDPM limiting the amount of current pulled from your source. Although your source is 5V and 3A, it is possible the resistive path between your source and the charger is causing a significant drop in voltage at the VIN pin. The voltage dropping down to the Input Voltage Limit will prevent additional current from being pulled and this will cause a reduction in your charge current. If you reduce the resistance between your source and the VIN pin, or if you reduce your Input Voltage Limit, do you see an increase in charge current and does increasing Input Voltage Limit reduce charge current? 

    (Please note that Input Voltage Limit shouldn't be within 120mV of the battery voltage since this can result in the device entering sleep mode if it is being regulated by VINDPM)

    700mA ICHG Case:

    This case does not seem to indicate that VINDPM or IINDPM is limiting the amount of current to be charged, however with the battery voltage of 4.15V and a battery regulation voltage of 4.2V, it is possible that the device is entering the CV stage of charge, which will naturally reduce charge current. If you keep increasing battery voltage slightly, does the charge current continue reducing? If you raise the "Charge Voltage Limit" does your charge current increase if you keep battery voltage at 4.15V?

    Best Regards,

    Juan Ospina