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BQ2973: Schematic review for two BQ29737 in parallel

Marvin Gasis Arcangel
Genius 9705 points
Part Number: BQ2973
Other Parts Discussed in Thread: BQ24040

Hi Team,

Can you please help check the schematic for two BQ29737 in parallel below?

The target system has got two Li-Ion Batteries. Each battery is protected with a single BQ29737. The batteries are then connected in parallel to provide a nominal voltage of 3.5V. There is a single Charger IC type: BQ24040 to charge both batteries.

In the case of an over-discharge situation, both protectors disconnect the batteries from the system. After then activating the charger IC, only one battery gets charged and the other one stays in the over-discharged state.

Coul you help troubleshoot the issue? Thanks in advance.

Regards,

Marvin

  • 0
    TI__Mastermind 34030 points

    Hello Marvin, 

    Using two ICs for batteries in parallel is not required and not a recommended configuration. A single IC would be able to protect the batteries.

    Differences in the battery voltages may cause one to discharge on the other one. My guess is that this is causing a protection fault when they are greatly mismatched, causing the protection to trigger and keep the cell OFF. What happens if you momentarely short V- and BAT-? This should turn-on the device.

    Regardless, I greatly recommend that they use a single IC for both batteries in parallel.

    Best Regards,

    Luis Hernandez Salomon