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BQ2063: After long shelf duration in storage mode is a new calibration cycle needed to eliminate accumulated SOC offset?

Part Number: BQ2063

HI There,

I have an URGENT question on the BQ2063 from my customer.

After a long time (6 months up to 1 year) in “Low power storage mode”,a customer starts using the batteries and there’s an offset in the gas gauge reading vs the real state of charge of the battery. The battery is full (12.6V) although the BQ2063 indicates a much lower state of charge (75%, 50% or even lower). This situation seems to worsen over time. Its the offset in the SOC reading that is causing the problem here and gets larger over time.

Our question is: is it mandatory to perform a calibration process after a long time in “Low power storage mode” for the BQ2063?

This does seem to resolve the problem but we were wondering why this drift/offset is occurring? Is there a better way to resolve this?

Here are the steps when they first get the battery before it gets shipped out to their customer:

  • Calibrate the battery;
  • Adjust the state of charge to 30% (for customer delivery);
  • Activate the low power storage mode;
  • Customers use the battery after many months, even up to 1 year.

 

Thanks,

Mark

  • Hi Mark,

    This is an old CEDV gauge. The change happens because there is a compensation for light dsg at using the predetermined value stored in the Light Discharge Current EE 0x64 register. Over time this can accumulate and can reduce the capacity. One solution is to reduce it to 0, this way storage more current would not affect the capacity.

  • Thank you for the quick reply!

    So for new packs, its best to reduce the value or make it zero in the 0x64 Register (Light discharge Current Reg). But for existing packs on the shelf, running another calibration will need to happen to zero out the existing offset. I don't see a way around this?

    Will contact the customer and let me know on the above. Thanks!

  • Thank you, unfortunately that is the way to do it.

  • HI there,

    Quick Question.

    We took a look. “Light discharge current”  reg 0x64 value is 0mA in the Bq2063 so this isn't the cause..

    Looking at the Datasheet for the BQ2063, there is register 0x01C (Pack load estimate) that also looks like it could have an impact on this generated offset. To quote the datasheet - "bq2063 applies the compensation in addition to self-discharge. The compensation occurs at a rate determined by the value stored in Pack Load Estimate EE 0x1c. The compensation range is 0 µA–700 µA in steps of approximately 2.75 µA"

    In the customer's pack, this register has the value 245µA value in the 0x1C. Can you confirm that this would also contribute to the offset and by reducing this register to 0, should reduce this accumulated offset?

    I would thnk yes, but wanted a sanity check. Thanks!

  • Yes, this can certainly affect it. You are correct. Please contact us if you have further questions.