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BQ25171-Q1: bq25171-q1 Design review

Vayne Li
Intellectual 1000 points
Part Number: BQ25171-Q1

Tool/software:

Hi Teams,

The customer set VSET for 4 nickel metal hydride batteries according to the recommended 15K, but it seems that they are not charging.

Please help check if there are any issues with the design

The batteries are all fully charged. They asked the battery manufacturer if they could afford 9W, but the customer's power consumption is less than 6W. When the external power supply is cut off, the battery is directly 2.8V. VBAT-4V8 on the picture is the battery.

  • +1
    TI__Guru* 75756 points

    Hi Vayne

    The input voltage may be the problem, looks like 5V on schematic.  Drop out voltage at 200mA is about 250mV.  Voltage remaining for cell, 5V -.25V=4.75V, or just under 1.2V / Cell. Which is low, probably need about 1.5V / Cell to charge.  From a 5V supply can probably charge 3 Cell. 

    Also note that the recharge voltage is 1.33V / Cell.  During charging the battery voltage must reach this point before timer expires or a fault is set.