• State TI Thinks Resolved
  • Locked Locked
  • Replies 8 replies
  • Answers 1 answer
  • Subscribers 66 subscribers
  • Views 2016 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

BQ2970: can't charge even the battery voltage is 2.83V

user4656546
Intellectual 475 points
Part Number: BQ2970
Other Parts Discussed in Thread: BQ25100

We used BQ25100 and BQ29700 in our product.

BQ29700 can cut off the voltage when battery voltage is under 2.8V, so the overdischage protect function is OK.

but we insert a 5V usb for charging and  BQ25100 can't charge, battery voltage is 2.83V. it was protected by BQ29700 but why?

I checked the NMOS connect to Cout, the GS voltage(to pack-) is 1.8V, it's high.

the NMOS connect to Dout, the GS voltage is 0V(to VSS), I guess it should be right? but why pack- voltage is higher than VSS so that it can't charge?

the max Vgh th of NMOS is 1.25V.

Pls see below cicuit.

  • 0
    TI__Expert 6085 points

    Hi,

    Seems there is an issue with the charger detection. For the charger detection, the difference of {V- - BAT} > 1.3V

    In this device o-V charging is always ENABLED. Hence Vochg is the min voltage that has to be given by the charger when its initially connected that will allow the battery to charge. Voinh, anything less , the protector will not allow charging.

    hope this helps out.

     

  • 0 in reply to Vish Nadarajah
    Intellectual 475 points
    Got it.
    but how can improve this?
    Does BQ29700 had problem or BQ25100 has probelm , or the USB power supply has problem?
  • 0
    Prodigy 40 points

    I'm testing with user4656546

    Battery cannot be charge while it's below 2.9V.

    V- to Bat with 1.8V

    We have already testing with the BQ29700 demo board

    Contact Battery- to Cell-, Battery+ to Cell+, Pack+ to Circuit VCC4, Pack- to Circuit GND

    The performance is the same. Battery cannot be charge while it's below 2.9V.

    For BQ29700, it support 0VCharge (1.7V), we are confuse why it cannot be charge battery voltage <2.9V.

    Can someone help?

  • 0 in reply to Neo Yuen
    TI__Expert 6085 points
    With the V- to BAT > 1.3V ( 1.8V in your case), the power down state should be released. if the battery is being connected for the first time, try shorting the V-pin to the VSS pin.
    What is the DOUT and COUT state?
  • 0 in reply to Vish Nadarajah
    Prodigy 40 points

    Battery always connected in the circuit. I'm still try to short the V- with VSS

    Still cannot be charge & current draw from battery ~450uA while shorted.

    While the Battery <2.9V & plug the USB for charging

    Battery = 2.88V

    CellN to Dout = 0V

    Pack- to Cout=1.831V

    V- to BAT=1.81V

    CellN to Pack-=1.056V

    Please help & thank you for reply.

    Right now, we are checking the BQ25100 charging curent

  • 0 in reply to Neo Yuen
    Prodigy 40 points

    After we increase the charging current from 10mA to 14mA, unit can be charge even ~2.0V

     But I still have something to ask

    After revise the charging current, one of the testing unit fail after testing for a serval time & low voltage

    Case is :

    Unit can be charge >2.0V in the beginning tested serval times.

    Then I try to drop the cell to more low voltage to test some extreme case. Then I short the cell with resistor to make 1.5V

    Put it back to the circuit & want to charge it.

    Current is jumped once & unit cannot be charge.

    After that I try the unit for >2.0V, 2.7V, unit cannot be charge.

    Are something happened while I test it with 1.5V??

  • 0 in reply to Neo Yuen
    TI__Expert 4640 points

    Please keep in mind that if battery is too low the protector won't allow charging. Please refer to the datasheet under 0-V charging available.

    Thanks

    Miguel

  • 0 in reply to Miguel Angel Rios
    Prodigy 40 points

    We know the qb29700 0v charge to be 1.75

    & below 0.75V will not be charge up again

    So we try some cases for the middle.

    It's seem there are some happen while we try 1.5V.

    Right now 2pcs of our unit after testing with 1.5V

    cannot be charge when the battery is below 2.9V

    Other unit which haven't test with 1.5V

    Are work well even the battery voltage>2.0 V only

    Suppose cut off @ 2.8V is difficult to drop to below 2.0V

    We are just interested with what is happening while testing with 1.5V.