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Original question:

BQ27542-G1: How to reserve the capacitor?

BQ27542-G1: remaining capacity

Minqi Zhao
Intellectual 1660 points
Part Number: BQ27542-G1

Dear expert,

My customer is using BQ27524-G1 in cell phone. After the phone's battery is 0%, it still needs to be placed for one month. So the customer wants to reserve 125mAh in the reserve capacity register. But when the SOC is 0%, test the remaining capacity is only 100mAh, less than 125mAh. The terminate voltage is 3150mV, load is 180uA. 

To explain the problem, I have two questions.

1. Can you help to explain the meaning more clearly of below content?

 

2. What's the meaning of reserve Cap? What's the impact? Thanks for your support.

  • 0
    TI__Guru** 105590 points

    Hello Minqi,

    The reserve capacity setting will show 0% Remaining Capacity at the point the battery has the amount of reserve capacity specified.

    Has a complete learning cycle been done and configured on the gauge? Without a successful learning cycle it could cause the gauge to miss the 125mAh programmed reserve capacity.

    Could you send a log file of the discharge and the .GG file of the configuration?

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    TI__Intellectual 1660 points

    Hi Keller,

    Thanks for your reply. I'm getting customer to send the log and gg file.

    But I still have one question to explain to customer. I'm confused about the yellow part word, could you help to explain " A loaded rate or no-load rate of compensation can be selected for Resreve Cap by setting the [RESCAP] bit in the Pack Configuration data flash register. This is a specialized function to allow time for a controlled shutdown after 0 RemainingCapacity() is reached"? Thanks for your support.

  • 0 in reply to Minqi Zhao
    TI__Mastermind 24870 points

    The loaded rate is a simulated reserve capacity similar to the gauge if it is running with a load current.

    the no load rate is using just a standard subtraction from the computed remcap.