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BQ25171EVM: Design Help

Part Number: BQ25171EVM

Hi,

Good Day.

I am currently evaluating the Bq25171 to power a solar device. The solar PV is 5V/10W rated and the battery is a 1S, 3.2V, 13.5Ah LiFePo4.

I have set VSET=82k (1-cell LiFePO4: 3.60 V), CHM_TMR=62k (Li+, no timer), TS=10k (No NTC) and ISET=R750 (400mA).

Without any load and Vin=5V from a stable power supply, I have the battery charging at 3.4V/0.4A, STAT1=LOW, and STAT2=HIGH.

STAT2 means that the chip founds a recoverable default and 3.4V is not the programmed voltage of 3.6V.

Could you please tell me if the configuration is correct and if there is a way to get STAT1=HIGH and a 3.6V?

Please advise. Thank you very much.

Best Regards,

Ray Vincent

  • Hi Ray,

    Just want to confirm,

    1. the test is done on the EVM?

    2. Is the battery connected to the EVM? If the battery is at 3.4V, the battery voltage will not move to 3.6V until fully charged based on the VSET setting.

    3. Do you measure 0.4A when plug in the battery at 3.4V?

  • Hi Jing,

    Good Day.

    1 Yes the test is done on the EVM.

    2 The battery is well connected to the EVM. You are right the battery was not fully charged and after 10 more hours the voltage reached 3.5V then protection cut the charge. However STAT2=HIGH and STAT1=LOW during the whole process. Is it related to the selection of "no timer" or something else?

    Best Regards,

    Ray Vincent

  • Hello Ray

    I am working with Jing on the BQ25171.

    Following up on the above question -- During the 10 hr charge what current do you see going into the EVM?

    This would also be the current going into the battery.  Should be 400mA and will decrease as the battery voltage gets near 3.6V.  But charge will not start if the battery voltage is above 3.4V.  To start a charge the cell voltage must be 200mV less than 3.6V.

  • Hi Bill,

    Good Day. Do you have the fact that stat2 always equals high and stat1 always equals low? Even after a successful charge, I have the stat2 On = recoverable default. Could it be linked to high battery capacity (13.5Ah) or the timer disabled?

    Please advise. Thank you very much.

    Best Regards,

    Ray Vincent

  • Hello Ray

    Couple of things to check out:

    1.) Check resistance from TP9 (VSET) to GND, should be 82k

    2.) Check setting of Switch S1, left side (resistors) is OPEN and Right side (PCB) ON

    Down = Selected

    Below Pic is correct setting for 4.2V (18k) at TP9

  • Hi Ray

    Any update on the BQ25171 evaluation board test?