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BQ24105 STAT1 pin flashing

Carl Nicholl
Prodigy 10 points
Other Parts Discussed in Thread: BQ24105

Hi,

 

We are using the BQ24105 charger chip. The charger is set up for single cell charging and current limited to 500mA charging. On connecting a battery or dc source the charge led Stat1 comes on. However when the battery volts is a 4.09v and charge current has dropped the charge led STAT1 flashes and never indicates fully charged STAT2 on. Using a dc source if I set the voltage to 4.1v the charged led STAT2 turns on.

The datasheet only mentions 104,108 and 109 as having blinking status pins. What is the 105 indicating? Is it one of the faults listed for the blinking status pins?

 

Thanks

 

Carl

  • 0
    TI__Guru 56650 points

    I would think the output resistance (battery internal resistance + the wire resistance between battery cell terminal and charger output) is too high.

    For example: changing current is 0.5A. The output resistance is 0.22ohm. The votlage drop is 0.5Ax0.22ohm=0.11V. Charger output is 4.2V(4.09_0.11). But, the battery is only 4.09V. 

    So, the charger runs to termination (fully charged). STAT1 flips.  After the termination, the charger output will follow the 4.09V battery voltage. It is lower than recharger threshold. STAT1 flips again.

  • 0
    Intellectual 270 points

    Hai

     

     We are using the BQ24105 for charging 3 cell Battery and current limited for 1amps.On connecting a battery its start charging , after reaching particular voltage it shows the eror in indication as per datasheet.The battery voltage designed for 12.5v.Please clarify.

     

    Regards

    Rajasekaran

     

  • 0 in reply to Raja sekaran
    TI__Guru 56650 points

    Are you use the same circuit as ?

    After reaching particular voltage... What the particular voltage is? What charging current is at that particular voltage? If the output resistance is too big, Rout x Iout =Vsetting -Vparticular, the STAT1 pin voltage may flash.

    What is Vcc pin voltage at that condition? If Vcc is lower than that Vparticular, the bq24105 runs at sleep mode.

  • 0 in reply to Wang5577
    Intellectual 270 points

    I am used circuit as like BQ24105 development.

    While I am plug the adapter its start charging.after particular time (near by 4 hours) its start show the error message.

    Actually there is no blinking,both status are high and charger IC keep status pin high even 5 hours.

    Once we unplug and plug the adapter then only its start charging.

    The same issues continue for last 5 charging cycle.

    Input adapter voltage - 14.5 volts

     

  • 0 in reply to Wang5577
    Intellectual 270 points

    I am used circuit as like BQ24105 development.

    While I am plug the adapter its start charging.after particular time (near by 4 hours) its start show the error message.

    Actually there is no blinking,both status are high and charger IC keep status pin high even 5 hours.

    Once we unplug and plug the adapter then only its start charging.

    The same issues continue for last 5 charging cycle.

    Input adapter voltage - 14.5 volts


  • 0 in reply to Raja sekaran
    TI__Guru 56650 points

    According to your new post, the charging was stopped after particular time, not particular voltage.

    The Cttc is 0.1uF on the datasheet application circuit. The fast charge safety timer is about 260 minutes. It is similar as the particular time (near 4 hours).

     

  • 0 in reply to Wang5577
    Intellectual 270 points

    So what i do for avoiding this issue.

    battery specification - 11.1v,8800 mAH

    Charged upto 12.45 v

    We here used 0.1 uF in TTC.

    Please clarify .

     

    Regards

    Rajasekaran

     

  • 0 in reply to Raja sekaran
    TI__Guru 56650 points

    On the datasheet page 16th:

    Tying TTC high disables the safety timer only.

     

     

     

  • 0 in reply to Wang5577
    Intellectual 270 points

    Hai,

     In our project we used 11.1V, 8.8 AH  LI-ION battery.

    Max voltage - 12.45v.

    Once it reach full charge the charge terminate correctly.

    We keep the input 15v as same, now load start drain the battery.

    Whats the minimum voltage its start again charging.

     

     

  • 0 in reply to Raja sekaran
    TI__Guru 56650 points

    If you use bq24105/125 and charging votlage setting is Voreg, the minimun recharge voltage is Voreg-125mV x Voreg/(2x2.1V).

     

  • 0 in reply to Wang5577
    Intellectual 270 points

     In our design we used BQ24105, Based on your reply recharging minimum threshold voltage is based on the below formula

    Voreg-125mV x Voreg/(2x2.1V).

    Let our maximum Charging votage = 12.45V

    So Voreg = 12.45V or Voreg is = 2.1 V

    If Voreg is 2.1V then it start charge again in the voltage of 5.75V,

    Please Clarify.

     

    Regards

    Rajasekaran

  • 0 in reply to Raja sekaran
    TI__Guru 56650 points

    The Voreg is 12.45V on that equation. So, the minimum recharge voltage is 12.45V- (0.125Vx 12.45/4.2)=12.45V-0.37V =12.08V.