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BQ25171EVM: Usage in 7.4V, 2 cell, Li-ion polymer Battery

Jacob S
Prodigy 90 points
Part Number: BQ25171EVM

Tool/software:

HI Team,

This is Jacob from e-con systems. 

I'm using 2 cell Li-ion polymer battery with 7.4V. 

I'm use this EVM to validate the charging circuit with my battery. values set, VSEL- 6.2K, CHM_TMR- 100k, ISET- 750E.

While validation STAT 1 LED is glowing constantly. 

But battery charging is not happening. Can you let me know, What are all the things I have to check.

Thanks in advance. 

Jacob S 

  • 0
    TI__Guru* 75806 points

    Hi Jacob

    STAT 1 ON and STAT 2 OFF will be a Recoverable Fault condition.  Vin OVP, BAT OVP or TS.

    VSEL- 6.2K  ---- This would be 2 Cell LiFePO4 (7.4V)  

    CHM_TMR- 100k  -- Li+ 5hr 

    ISET- 750E.--- 400mA charge current

    Recommend changing VSET to 3.6k, position 7 -- this is 2 Cell LiIon (8.40V) Which will work for Li Polymer also. 

  • 0 in reply to Bill Johns
    Prodigy 90 points

    Hi Bill

    Thanks for your suggestion. It is working after changing VSET to 3.6K. 

    I have some more questions.

    1. After changing VSET to 3.6K, battery is charging. But STAT 1 LED is glowing and STAT 2 LED is in off condition. You have mentioned this as recoverable fault condition. What can we do further to clear this? 

    2.  While this charging process, We have not connected battery NTC output to the EVM. If we connect NTC pin to EVM STAT 1 LED is in OFF condition and STAT 2 LED is glowing. And the battery is not charging. 

    3. Can we charge this same battery while giving input voltage from USB.(5V, 500mA) If not, Do we have any other IC's which can charge this battery with the USB input. 

    Looking forward to your answers. Thanks.

  • 0 in reply to Jacob S
    TI__Guru* 75806 points

    Hi Jacob

    Jacob S said:
    1. After changing VSET to 3.6K, battery is charging. But STAT 1 LED is glowing and STAT 2 LED is in off condition. You have mentioned this as recoverable fault condition. What can we do further to clear this? 

    A recoverable fault and Charing are similar:

    Charging STAT1 -- OFF, STAT2 -- ON

    Fault        STAT1 -- ON , STAT2 -- OFF

    No reset or clear is needed.  Double check the LEDs.

    Also charge current can be monitored at ISET pin, voltage is proportional to output current.  During the CC phase it will be 1V.

    Jacob S said:
    2.  While this charging process, We have not connected battery NTC output to the EVM. If we connect NTC pin to EVM STAT 1 LED is in OFF condition and STAT 2 LED is glowing. And the battery is not charging. 

    When the NTC is connected check the voltage at TS to ground should be about 0.380V , above 1.04V is coil shutdown and below 0.188V is hot shutdown.

    When connecting battery pack NTC to EVM removed JP6 shorting Jumper, should be open.

    Jacob S said:
    Can we charge this same battery while giving input voltage from USB.(5V, 500mA) If not, Do we have any other IC's which can charge this battery with the USB input. 

    Yes a 5V 500mA input will work with this EVM, 4.2V and 400mA charge current.