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Need help on BQ77PL157A4225

Aravind .R
Genius 3175 points
Other Parts Discussed in Thread: BQ77PL157A4225

Dear All,

one of my customer is using BQ77PL157A4225 and they are facing following issue, kindly need help to resolve the same.

In this one they are using the 4 series CELL'S Model.as per the drawing mentioned from the Datasheet. so in this they are facing one Problem and they are charging this battery management system through solar panel or Power supply   and with that higher cutoff happen to batteries  at 16.9V( any one cell reaches to  4.225 as per mentioned in datasheet 4X4.225 ) and after higher cutoff happens they are unable to identify where is reconnection point for charging by changing the CD Pin Capacitor values in the system as per data sheet and in this one they have observed one point that when it was in reconnection  voltage drops below  15.2V to 15.4V  with load or without load on the battery irrespective of the CD capacitor value its happening can you please suggest me the solution for this.because theywant to set the reconnection value to 16.2V.

Aravind.

 

  • 0
    TI__Guru 54715 points

    The part will trigger the fault at 4.225 with the tolerance and will time with the CD capacitor as shown in Figure 5 of the datasheet.  At nominal the 4 cell system voltage would be 16.9V as you indicate.  The part will recover after the voltage falls by the Overvoltage Detection Hysteresis VTH which is between 150 and 450 mV on each cell, so the 4 cell system voltage could be 16.3 to 15.1V, or less if only 1 cell were triggered.  Once the (VPROTECT - VTH) recovery threshold is crossed the CD capacitor will again delay the switching as shown in Figure 5.  Changing the CD capacitor values will not adjust the recovery voltage but will adjust the delay or what might be though of as a de-glitch time.

    This voltage protector does not offer the recovery threshold adjustment which the design seems to want.  It may be possible to select a gauge with programmable trip and recovery thresholds, a gauge would of course require more setup but provide more features than the protector.  You might look for products at the fuel gauge page http://www.ti.com/lsds/ti/power-management/battery-fuel-gauge-overview.page or the experts in the fuel gauge forum may have specific recommendations.