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BQ34Z100-G1: Connecting/disconnecting battery from the IC

Julian Antonacci
Prodigy 70 points
Part Number: BQ34Z100-G1
Other Parts Discussed in Thread: BQ27421-G1

Hello,

I was looking for a solution to a Li-Ion battery SOH monitoring but in my particular application, the two batteries will be galvanically isolated from all circuitry when discharging and will be connected again when charging. I do not know if the SOH value read with the BQ34Z100-G1 after charging will have any accurate or not and I can't answer it from the datasheet.

I will be using a 3350mAh LG Energy 18650 Li-Ion Battery.

Thanks in advance, Julian.

  • 0
    TI__Mastermind 24870 points

    Hello Julian,

    The SOH computation is only for discharge mode. As long as the gauge is connected to the battery and it is allowed to go through Qmax and Ra table updates, and we are able to take qualified OCV readings, the SOH should be okay.

  • 0 in reply to Kang Kang
    Prodigy 70 points

    Hello, thank for your reply:

    The battery will be connected to the gauge when its level is around 50% and will remain connected up to full charge. Lather, the gauge will be disconnected at the same time the load is connected to the battery.

    I want to know the SOH after charging just before disconnecting from the gauge. In the datasheet do not found that this IC is able for connecting/disconnecting battery. I would be a better option the bq27421-G1?

    Thanks again, Julian

  • 0 in reply to Julian Antonacci
    TI__Mastermind 24870 points

    Hello Julian,

    It is better to use a pack side gauge where you do not put the gauge through re-initialization. The gauge needs a good DOD/OCV reading at first boot. During initialization if there is current flowing, then the re-initialization will fail.

  • 0 in reply to Kang Kang
    Prodigy 70 points

    Hello again, is not possible tu use pack side gauge. I need it to be charger side. If I put the batter with out charger breather load at the reinisialization for a OCV read, does it improve measurements? How much time of DOD measurement does the IC needs before SOH actualization? Because I can put a resistor to discharge battery at 20mA for that time to get the measurement.

  • 0 in reply to Julian Antonacci
    TI__Mastermind 24870 points

    Hello Julian,

    If the charger can provide current to the system and we wake up the gauge with no current flowing through the sense resistor, then it should help. Otherwise, the gauge should be able to correct for the initialization the next time it takes an OCV measurement.