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bq27542-g1: Questions about configuring the gauge and performing a learning cycle.

lance fisher
Prodigy 120 points
Part Number: BQ27542-G1
Other Parts Discussed in Thread: BQSTUDIO

I finally got around to working on configuring the fuel gauge IC for our battery.  I successfully performed a data collection and submittal for the online GPC (Chemistry Matching Tool) and have obtained a Chem ID (1353) and loaded that into the fuel gauge.  Now I’m trying to get the learning cycle working.  I’m attempting to follow the procedure in the datasheet and am encountering several problems and have some questions:

 

  1. The bq27542 datasheet says to use the “bqConfig Tool” to set the chemistry ID.  Is that the same thing as the Chemistry tab/window in bqStudio?  If not, where do I find the bqConfig Tool?

 

  1. Is the Chem ID in the CPC report a decimal or hexadecimal number?  It appears that when I selected that ID in the bqStudio Chemistry window the fuel gauge took it as a hex number (the CHEM_ID button in the Commands pane returns “0x1353”) and I’m wondering if I’ve got something wrong there.

 

 

  1. In addition to selecting the Chem ID, what other parameters that must be set correctly before performing a Learning Cycle. I’ve set the following ones: Charging Voltage, Taper Current, Dsg Current Threshold, Chg Current Threshold, Quit Current, Design Voltage, Design Capacity, Design Energy, and Design Energy Scale, are there any more?

 

  1. After running what appears to be a valid Learning Cycle only the first Ra0 table was updated (Ra Flag = 0x0055).  The second table (Ra0x) still has default values (Ra Flag = 0xffff) which are very different than the ones in the first table.  Does this matter and if so what do I need to do to get the second table to update?

 

 

  1. The parameters called Ra Filter, Ra Max Delta, Max Res Factor, and Min Res Factor appear to affect how the Ra tables are updated.  Do they apply during a “Learning Cycle” and if so do they need to be configured to allow a complete replacement of the table values.  The datasheet indicates that with the default values for these parameters the updated Ra table values will reflect only 20% of the newly measured readings while retaining 80% of the pre update values.

 

  1. After the Learning Cycle completed (Update Status = 6) the Qmax Cell 0 value is 203 mAh (changed from 210), the FullAvailableCap is 202 (changed from 209), the FullChgCap is 179 (changed from 186), and the and the SOH is 32%.  Given the Design capacity of 630 and the fact that a 122mA (C/5) discharge took almost 5 hours shouldn’t those capacity values be close to 600 or more and the SOH close to 85 or 90?

 

 

  1. During the charge and discharge portions of the learning cycle the Registers window of bqStudio and the logged register data indicates that the Average Current is only  100 to 101 and -40 to -41 mA even though the GDK was configured for a charge current of 300mA and a discharge current of 122mA.  The bqStudio Dashboard shows 298 and -121 mA and I have confirmed those readings with a calibrated voltmeter.  Why is this happening and is it responsible for the low Qmax?

 

  1. During several of my attempts at performing a successful Learning Cycle I have found that the register value log contains several consecutive rows containing no data and a LogStatus value of “ERROR : Please check D:\QCI_Projects\Vima\BatteryLogs\LearningCycle4.log.err”.  In at least one case the logStatus returned to “SUCCESS” after 882 rows of errors.  The resumption of successful logging occurred on the exact same row as the GCK transitioned from Relaxation after discharging to Charging.  My logging interval is 10 seconds.  The bqStudio Dashboard auto refresh was on and Data Memory Auto Export was enabled with a 10 minute interval.  What is causing this and how can I prevent it?

 

  1. I used the bqStudio GDK “Auto Cycle” function to run the Learning Cycle because every time I try to use the “Learning Cycle” function in bqStudio the logging fails (similar to what was reported in #8 except the logging never resumes), and the bqStudio program would often crash in that mode.  I began the run with a nearly discharged battery and started with a discharge cycle. The first discharge only lasted 23 minutes. The GDK was configured with a Charge Voltage of 4200mV, 300mA charge terminated by FC setting followed by a 120 minute relaxation and then a discharge constant current of 122mA with a cutoff at 3150 mV (my pack protection disconnects at 3100 mV followed by a relaxation period of 300 minutes.  I let the auto cycle continue until one full charge period and a second discharge/relaxation period completed.  With this method, when should I reset the fuel gauge and when should I enable IT?

 

  1. On the bqStudio Dashboard there is a round gauge with a scale from -2000 to +2000.  It appears to graphically (and numerically) display the same bogus “Average Current” as is shown in the Registers view and recorded in the Log.  Where does this value come from ? 

-lance