BQ40Z50: CC Auto Offset/CC Auto calibration

Hi,
would like to join this thread as I think I am having a similar topic: I have a battery with BQ40Z50R3 which very sporadically fails charging; the abort of charging is caused by the charger not seing any current feedback in the first 10seconds after battery is inserted into charger.
Recorded data shows that there really is current flowing (charger reports charging current), but battery does not report any current feedback (both actual current and average current remain 0, though I2C communication with battery is ok (battery is asking for voltage (command 0x15) and current (command 0x14)); based on this I assume that this is due to the auto calibration being active at this time.
So my intention would be to modify the charger logic for this and increase the delay time (by the 16seconds auto calibration time).
However I cannot find a way to check this as I cannot find a way to force the auto calibration for the battery. 
For BQ40Z50, based on the documentation, autocalibration should be done if
- auto calibration is enabled (CC Auto config = 0x03)
- auto calibration was not done for the last 10hours (to prevent wear out)
- system is entering  sleep mode

My trials to test the modified charger logic right now are:
- make sure the battery is not used for >10hours
- activating the battery (e.g. by connecting to charger)
- shortly deactivate the battery (->auto calibration should be started now; question is how short) and immediatly activate again by putting into charger
  -> now I would expect the above situation with no current feedback of the battery

So additional question to HY are:
- is above test procedure correct? 
- is there any status information available on I2C showing that auto calibration is active (based on documentation no)?

Hi HY,

For clarification, which version of the firmware is being used?

HY said:

 1). In this E2E thread, I found the following info about the CC auto offset for bq28z610. Are all mechanisms also applied in bq40z50? 

• The first time CC auto offset is no 10 hours restriction.
• The 10hr requirement is for subsequent Auto CC offset calibration. 
• The auto CC offset calibration is initiated on entry to sleep mode, not after 10 hours in sleep mode.

I believe these structures are the same between the bq28z610 and the bq40z50.

HY said:

2). Is there any temp limitation or delta temp limitation for the CC auto offset?

I do not believe there is a temperature limitation on for the completion of the CC Auto offset.

HY said:

3). Will "the CC auto offset" work in the sleep mode if the customer disabled the sleep mode but set CC Auto config=03?

Since the AUTO_NESTON relies on the offset being taken, to which the auto CC offset takes its measurements in sleep, I believe that entering sleep would be required still. However, I believe this could work if the CC Offset calibration is done manually.

Regards,

Anthony Baldino

Hi Werner,

If possible, please create a new thread with the information above. This allows us to engage with our user's questions and concerns more efficiently.

Regards,

Anthony Baldino 

Hi Anthony,

Thanks for your reply. The customer might use v3.09 or the later version. 

For 2), Because our bq40z50 HW said the recommended operation temp will be -40dgeC to 85dgeC. Based on that, just double confirm, does the FW have an operation temp range for CC auto offset?  

One more question, regarding to the CC auto offset behavior should be the same in the all bq40z50 FW, am I right?

Hi HY,

When looking through the firmware, I did not see any temperature restriction for the CC auto offset calibration. I believe this should be functional across the entire operating temperature range of the device.

Correct, the behavior of this calibration should be the same across all firmware versions.

Regards,

Anthony Baldino