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BQ2004: Charging time

Yang Lou
Prodigy 20 points
Part Number: BQ2004

I designed a battery charger with BQ2004E for 4 cells Nimh battery(10000mah). I found the charger will always stop fast-charge before it's completely charged and the time seems shifts in the table in datasheet. For example, I set TM1 and TM2 as low/low, fast charge safety time should be 325min, but it always stopped at 150min, which is for next level setting. But if I changed to Float/Low, which should be 154min, fast-charge will stop at 69min.

So the fast charge time in my experiment is 150min, 69min, 35min, 17min, 9min, 77min, 37min, 9min. All of them are only half of the time supposed to be. Anyone can give me an idea about it?

I also purchased an development board which used BQ2004H and it did same thing(same fast-charge time). But it is only quarter of the time supposed to be.

  • 0
    TI__Guru 56650 points
    bq2004 was released over 18 years. I never heard the timer issue before. If an EVM shows only quarter of the time supposed to be, I would think other termination methods may kick in and stop charging or the board component value is wrong.
  • 0 in reply to Wang5577
    Prodigy 20 points

    Ok, thank you, so another question is, if the battery is fully charged, the board should not charge to battery again when I reconnect the power supply, right? But when I reconnected the power supply, the board could still charge the battery for another cycle. Does it mean the chip cannot fully charge battery? Or it will charge even if the battery is full?

  • 0 in reply to Yang Lou
    TI__Guru 56650 points
    After reconnect the power supply, the charger re-start the charging routing. No matter the full charge or not because customers could change the battery which has different voltage or characteristics.