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Suddon drop of 0.2 Voltage while unpluging the charger.

ela_embded_engineer
Prodigy 95 points

while usb adapter of 1A is connected it is charging normally, but while unplug the power source ,there is a sudden voltage drop of 0.2v which makes a huge drop in capacity .so this makes problem for application team to display the battery status .since i am a software guy i an not sure whether it is usual electrical characteristics or a problem . i dont know how mobile manufactures handling this one, did they handle this in application level by handling charger detection pin ? or its an hardware design bug ?  . but i am sure my fuel gauge value is correct since i checked voltage  with or without charger connected in multimeter also. fuel gauge showing the exact multimeter values !!!!

Thank you in advance

  • 0
    TI__Intellectual 2650 points

    Are they allowing a proper constant current , constant voltage charge profile, and not skipping the full constant voltage phase ?  You should check what the charging current is when they disconnect. If they have not allowed the charge current to properly taper to a small current  at the end of charge then when they disconnect charger they are going to see a larger drop when the IR drop across internal resistance disappears. eg if you have 1A flowing at charge termination the charge drop will be much bigger than if you tapered to say 100mA and stopped.

  • 0 in reply to Mike Ewer
    Prodigy 95 points
    But same thing happens while recharging. sudden rise from 3.6 to 3.9 and so . Is this cause of battery aging ? my battery data sheet says its charging cycle is >=300 . Now my battery should have reached inbetween 150-230 . Is this fact also should be taken into account ?
  • 0 in reply to ela_embded_engineer
    TI__Intellectual 2650 points
    The cell internal resistance is going to be a factor whenever you charge or discharge. If you taper charging current properly per cell manufacturers datasheet when you charge then the final cell voltage with no load should quite close to your charger voltage. When you add a discharge load, the voltage across the load will be a function of whatever the load's restance is and the cells internal resistance. So for example if you apply a light load ( higher R, small discharge current) the output will appear closer to the open circuit no load value but as you increase the load ( smaller R , higher load current) the voltage across the load will be lower as more voltage is dropped across the cells internal output resistance. As the battery gets older and/or at low temperatures it's internal resistance will increase compared to room temp value when new.