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Charging Li-ion battery with BQ25504

Arunabha Deb
Intellectual 710 points
Other Parts Discussed in Thread: BQ25504

Hi 

I want to charge a 3.7v,100mah,Li-ion battery with BQ25504 evm.I am giving an input voltage of 1.8 volt to evm.I want to know what should be the values of resistors to charge this battery.My Vbat output is only giving 2.7 v max.Please help me.

Thanks

Arun

  • 0
    TI__Mastermind 20570 points

    There are several thresholds you need to set based on your battery spec. Please see the datasheet page 12 figure 11.  

    VBAT_UV is the voltage threshold where to protect your battery from over discharging. Normally, for 3.7v li-ion battery, this should be 3V. Please refer to your battery spec sheet. 

    VBAT_OK is a GPIO signal to indicate the battery voltage is at a acceptable level. this depends on when you would like it to inform your MCU or any host device that the battery power is good.

    VBAT_OV is the voltage threshould where the VSTOR and VBAT will regulate to, normally for 3.7V li-ion battery, this should be around 4.2V. Again, you should refer to your battery spec.

  • 0 in reply to Jing Zou
    Intellectual 710 points

    Hi

    I read the tables for bq25504 design guidance.From there i got the values of R0v1 and Rov2 of 4.4Mohm and and 5.6Mohm for a VBAT_ov of 4.2.I am giving 1.8 v as input to bq25504.But at Vbat I am only getting 2.7 v max.I want to fully recharge my battery which is not happening.Please help me.

    Thanks

    Arun

  • 0 in reply to Arunabha Deb
    TI__Mastermind 20570 points

    First, please make sure that your power supply is not limitting the output current too low.

    Second, when you change the ROV1,and ROV2 make sure you clean the board very well. When you installed resistors>1Mohm, most of the new resistors using solder with flux, the residual flux can create parasitic, varying resistors in the 1Mohm range that are in parallel with your voltage setting resistors. If extreme cleaning with alcohol doesn't work for prototyping, try standing the resistors on their side (tombstone).