BQ34Z100-G1: Lead acid chemistry, do I need a new Chem ID? Failed learning cycles and incorrect calibration

Hi Evan, thanks for your response. I have tried calibrating the current numerous times but I always end up with a current reading as if it's charging, up to 2.5A measured. How do I get it so it reads 0Amps when no load or charging is taking place?

Hi,

Sorry I linked the same video twice. Here is the video for calibrating current.

Perform current calibration with the BQ34Z100-G1 | Video | TI.com

To clarify when there is no load applied, the gauge is reporting a discharge current of -2.5A? This is quite strange, but I would assume this is an issue with your calibration parameters. The gauge should report a positive current when the battery is being charged.  

Can you share your .gg file, so I may view the parameters.

Regards,

Evan

When there is no load applied, the gauge is reporting a charge current of 2.5A, this is including the scale factor of 14 so it reads a current of about 180mA. 

The gg file is attached below. As well as a screenshot of the current reading with no load or charger connected, showing 151mA this time.

 2642.91Data_memory_14-06-2024_Charge_.gg.csv

Hi Chris,

Please allow me sometime to try and replicate your issue.

Regards,

Evan

Hi Evan, 

The BQ34z100-g1 datasheet states "The value of the current sense resistor should be entered into both CC Gain and CC Delta parameters in the Data Flash Calibration section of the Evaluation Software." The value of the current sense resistor is 0.1mOhm. 

However the Data Flash summary table from the technical reference manual states the minimum value for CC Delta is 2.98E+04 . 

I'm using the evaluation module, but have replaced R30 with a 0.1mOhm Shunt resistor.

Thanks for your help so far. 

Chris

Hi Evan, 

When 0.1mOhms is entered in the data flash parameter CC Delta, BQ studio comes up with a message saying "Value is beyond maximum value defined for parameter." I guess because 0.1 is below the minimum value for this parameter. Is this a problem with my design?

Best regards,

Chris

Hi Evan, 

The maximum current possible from our application is 390A, so to keep the voltage drop within the recommended limit, our sense resistor should be 0.1mOhms. 390A x 0.0001 Ohms = 39mV. 

We could go for a 0.5mOhm sense resistor but that would mean the voltage drop across the resistor would be above the 125mV limit at 195mV.

In terms of inputting the parameter CC Delta, the minimum allowable is stated to be 2.98E+04, is this an error? 

Best regards,

Hi Evan,

Thanks for your help so far.

I'm still struggling to get this system working.

We performed a discharge and charge cycle over Friday and the weekend to upload to the gauging parameter calculator and confirm the CHEM ID. Please see the attached data log and .gg export file.

I've noticed that the CC GAIN and CC DELTA parameters are still at 1.376 and 1.374. I have set them to 0.1 in BQ studio but they default back to these numbers, why is this?

Also from the data log can you see the issue where the current doesn't rest at 0 mAmps, but at around 150 mAmps. Is this a result of the incorrect CC Gain and CC Delta parameters? I followed the videos for voltage, current and temperature calibration.

Could it be Chem ID, because I haven't had back a successful report Gauging Parameter Calculator report yet. 

I haven't yet tried to replace the 0.1mOhm resistor with a 0.5mOhm resistor but this is an option for the future. I'm concerned that the only 0.5mOhm resistors I can find are 5% whereas the 0.1mOhm resistor I'm currently using is 1%. 

Chem_Selection_03.zip28_06_24_Discharge.log71_28_06_24_Discharge.gg.csv

Hi,

Please use the calibration tab in BQstudio.

The data you gather needs to match the graph in the document below. 

Simple Guide to Chemical ID Selection Tool (GPC) (Rev. A)

Regards,

Evan

Hi Evan, 

The calibration tab only has options for CC Offset and Board Offset calibration and won't allow for setting CC Gain and CC Delta parameters which is what the software won't accept. Is there a way to set CC Gain and CC Delta in the calibration tab? 

Best regards,

Hi Evan,

I have recently ran the Chemical selection tool with the files attached and this is the report I received back. Some queries I have are that it thinks the discharge current isn't negative, which it is in the file. Also it suggests the discharge period is 0.001 hrs when it was more like 5 hours.  There was also a long relax period before the discharge started. Any help is appreciated. 

Chem_Selection_03 (2).zipChem_Selection_03 (2)-report.zip