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BQ25756E: BQ25756

sasi vp
Prodigy 30 points
Part Number: BQ25756E
Other Parts Discussed in Thread: BQ25756

Tool/software:

Please see below answer for your questions.
Hi,
Answer,
Are you using the EVM or a custom board? 
Ans.No
Does the BQ25756 come up to the battery voltage when there is no load?
Ans, Voltage is coming, is not stable.
Do you think there could be some type of load on the output of the BQ25756 that prevents the output from coming up?
Ans, No
If you replace the IC, does the behavior change
Answer: IC Not replaced. Two PCBs were checked, and in both cases, Deep discharged battery charging does not occur, but the charging LED is on.
Charging happens when battery voltage is present.
Could you please provide a proven charger schematic diagram for a  12.6V battery with a charging current of 3A. I will verify that all the components meet the requirement
Regards,
Sasi VP 
  • 0
    TI__Mastermind 31305 points

    Hello Sasi,

    Thanks for the new information. I'm posting your previous question here just for clarity.

    sasi vp said:
    I am using this charger IC as a standalone charger for my battery. However, I am encountering an issue when trying to charge a deeply discharged battery. The charger indicator shows that charging is active, but no current is flowing. The battery voltage before the protection circuit (PCM) is around 5V, but due to the under-voltage cut-off of the PCM, the voltage drops to 0V after the PCM. Could you please advise on how to properly charge this deeply discharged battery? Please note that I am not using I2C control for this application; it is a purely standalone setup

    I have a few more questions to help debugging:

    sasi vp said:
    Are you using the EVM or a custom board? 
    Ans.No

    Can you clarify this answer? Can you send me the schematic if you are using a custom board?

    sasi vp said:
    Does the BQ25756 come up to the battery voltage when there is no load?
    Ans, Voltage is coming, is not stable.

    This sounds like expected behavior. The charger should be going into charging the output capacitors, terminating charge, and then recharging the capacitors when the voltage drops.

    Also, can you measure the resistance across the terminals of the deeply discharge battery?

    sasi vp said:
    Could you please provide a proven charger schematic diagram for a  12.6V battery with a charging current of 3A. I will verify that all the components meet the requirement

    For a proven charger schematic, can you use the EVM? If you replace R64 with a 34.4kΩ resistor, the BQ25756 will charge a battery to 12.6V. You'll also need to replace the ICHG resistor with a 16.2kΩ resistor.

    Best Regards,
    Ethan Galloway