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BQ27441-G1: How to set Dsg Current Threshold

Star Xu
Genius 9645 points
Part Number: BQ27441-G1
Other Parts Discussed in Thread: BQ25606

Hi

My Customer use BQ27441 in low-power devise, the minimum power consumption of the device is 2mA, the battery capacity is 1000mAh, accord the TRM equation

current(mA) = Design Capacity / (Dsg Current Threshold × 0.1)

Calculate the Dsg Current Threshold = 1000 *10/2 = 5000(0.1h) out of the max value 2000

how to set this parameter?

Thanks

Star

  • 0
    TI__Guru 52115 points

    Hi Start,

    Dsg Current Threshold is the current threshold above which the gauge detects that it is in discharge mode.  A value below C/10 is generally reasonable.

    According to the definition of Dsg Current Threshold, you set Dsg Current Threshold to something like 120, which means the actual discharge current threshold is C/12 (about 83mA).

    Andy

     

  • 0 in reply to Andy Liu (BMS)
    Prodigy 40 points

    Andy,

    Thank you for your help! Now I also have some questions.We use BQ25606 as the charger and we have designed the maximum charge currnt 500mA.And I found the taper current of BQ25606 5% of ICHG and the accuracy is 5%.So I want to take the 25mA as the taper current.  According to the information I have got,I try to set other parameters like below,:

    Taper Rate = 1000 * 10/(25(1 + 5%)) = 380, Chg Current Threshold = 1000*10/20 =  500, Quit Currnt Threshold = 1000 *10/15 = 666;

    Are they OK?

    I'm looking forward to your repaly!

  • 0 in reply to user6299088
    TI__Guru 52115 points

    The taper current is 26.25mA based on your Taper Rate setting. The actual charge current threshold is 20mA and the actual quit current threshold is 15mA.

    Our suggestion is that Charge Term Taper Current > Charge Current Threshold > Quit Current and therefore these settings seem okay.

     

  • 0 in reply to Andy Liu (BMS)
    Prodigy 40 points
    Hi Andy,
    Thank you very much.Your suggestions are really helpful to me.
      Now I have anthor question.That's I see the battry should be discharged to empty(Terminate Voltage) and it should be relaxed for at least 5 hours,then it should be charged to full,then the battry should also be relaxed for at least 2 hours, then it should be discharged to the terminate voltage.
      Now my question is what's the meaning of this "Terminate Voltage". I spent a lot of time  searching  the forum,someone said the "Terminate Voltage" was the empty voltage which is about 3V,but the others said it should be the system minmum working voltage. It really confused me.I really want to know your suggestion.
  • 0 in reply to user6299088
    TI__Guru 52115 points

    Terminate Voltage is essentially the empty pack voltage where the gauge should ensure 0% state of charge is reported.

    If you do a learning cycle, this should be set to the minimum voltage of the battery as specified in the manufacturer’s datasheet, which is usually 3V for Li-ion cells. 

    After the learning cycle is completed, this value can be adjusted upwards if there is a need for the gauge to report 0% at a higher voltage.

     

    Andy

  • 0 in reply to Andy Liu (BMS)
    Prodigy 40 points

    I'v got it!Thank you!