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BQ2004H Charge controller

Manjunatha S2
Prodigy 50 points
Other Parts Discussed in Thread: BQ2004H, BQ2003

Hi

please find the circuit below, BQ2004H used as Linear mode charge controller and  settings are as follows

 a) Charge rate : C/8

 b)Termination:    -ΔV method and C/8

 c) Auto discharge and Temperature termination are not using.

BATTERY:   NiMH  pack (10 cells), 12V 1600mAh.

With these combinations, battery is charging for only  30 minutes . If i switch off the charge controller and switch ON again it will start charging and it will end for 20-30 minutes. Battery never reached full charge.

Please suggest me what will be the reason the battery is not reaching to full capacity.

  • TI__Mastermind 31120 points

    Why is the TS pin tied off to 5V?

    Maybe the part is terminating after the hold off period because of the TS bias.

  • in reply to Charles Mauney
    Prodigy 50 points

    Thank you charles

    As i said i m not using temperature based termination. 

    Accoding to the datasheet, If the potential between TS and SNS is less than the voltage at the TCO input, then fast charge or top-off charge is terminated.

    As per the my circuit design TCO input is 1.3V and TS = 5V. 

    TS is tied off to 5V because, to eliminate the temperature method fast charge termination.

    Please suggest me about this.

    Thanks and regards

    Manju

  • in reply to Manjunatha S2
    Prodigy 50 points

    Hi charles 

    I did small changes in schematic, TS is supplied with 1.73V and TCO supplied with 1.27V to meet the criteria of  Vhtf<Vtemp<Vltf. Then also no improvement in the charging.

  • Prodigy 80 points

    Hello Manjunatha

    I'm facing the same problem here using BQ2003 in a circuit similar to yours, and I can give you some tips that aparently (i'm testing continuously to check stability) are solving the problem. I'm trying to charge a 12Vx2500mAH pack using C/4 and the charge was ending with less than 1 hour. With this points, the charging time increase up to 2:30hs.

    1 - Take a look in the voltage ripple in your battery, try to keep it under 100mVpp. I'm using an inductor after the switching transistor in order to minimize it. Are you using a constant current source at VCHARGE for not using an inductor?;

    2 - Try to increase your capacitor parallel to your battery (~100uF) and use a low ESR capacitor.

    Hope we can find a solution for our problems

    Regards

    Renato Barelli

  • in reply to Renato Barelli
    TI__Mastermind 31120 points

    If the 5V regulator is not very stable, this can cause early termination since it uses this voltage for the DA conversion reference for determining termination.

    Use the regulator used in the UG.