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BQ25100: does not like my gauge

Fabien LETORT
Intellectual 385 points
Part Number: BQ25100

Hello, i am using the bq25100 to charge my small lipo (250mAh).

On my board i have also a gauge (not a TI one). When the gauge is not activated, the charge is around 2 hours to be done.

If i activate the gauge it can take 15minutes to 60 minutes more !

If i acivate also some led (a rgb led is on my board), more power i put on them, more the charge seems disturbed, as i can have around 8 hours of charge to be ok.

The BQ2500 seems really disturbed is something is working on the board during the charge ?

  • 0
    TI__Guru* 75786 points
    Hello
    Your system will load will be connected to the bq25100 output and battery, current out will be both current to battery and current system.
    For the bq25100 to complete charge it is expecting the output voltage to reach 4.2V and then output current to drop to lower value for termination. This termination value is set by the user (bq25100) and is typically 10% of the fast charge current, pin C1 PRE-TERM.
    What is probably happening is the additional system load is preventing the output current from dropping to termination value and bq25100 from indicating charge complete.
  • 0 in reply to Bill Johns
    Intellectual 385 points

    I don't know if it is this problem.

    I don't check the end of battery charging process wit the BQ25100. Without gauge activated, i know than in two hours the charge is ok, maybe less. I have a 250mA lipo and the Riset is put to 680ohm -> Icc = 200mA

    I notice only that when my gauge is activated, the charging process is longer. The gauge should only take 3uA. 

    But the gauge will show charge to 100% after between 2h15  and 3 hours (depending the device... but starting in all the case with a battery in the same state).

    So i was wondering if something can disturb the BQ25100 ?