BQ34Z100-G1: SOC Jumps Up During Relax

Hello Charles,

If the SOC jumps in relax when an OCV is taken then you may not have the correct chemID match, what chemistry are the batteries?

I would recommend using the smoothing feature to reduce jumps in SOC. If your batteries vary widely on temperature this could be a major issue for gauging if we don't have access.

Sincerely,

Wyatt Keller

Hi Wyatt,

The chemID should be fine, a couple of TI supporters have look at that. The battery is always placed inside the room, the room temperature is not changed significantly. The thermistor right now is basically measure the room or board temperature, rather than the battery cell's temperature. I don't know how critical the temperature affect in Ra or some other parameters modeling. 

Is there a way to stop updating these parameters, or stop OCV reading at relax mode? Currently, I have set the Load Select to 6 and update status to 2. For the products in the market, I don't need an accurate detection. I only need to have coulomb counting to measure the SOC, and the SOC should be consistent, not jumping up during relax mode. 

Thanks,

Charles

Chemistry ID selection tool, rev=2.47		
		
Configuration used in present fit:		
ProcessingType = 2		
NumCellSeries = 20		
ElapsedTimeColumn = 0		
VoltageColumn = 1		
CurrentColumn = 2		
TemperatureColumn = 3		
		
Best chemical ID : 6103	Best chemical ID max. deviation, % : 9.21	
		
		
		
Summary of all IDs with max. DOD deviation below 15%		
		
Chem ID	max DOD error, %	Max R deviation, ratio
6103	9.21	-34.49
		
Max. deviations for best ID is within recommended range. Chosen best chemical ID is suitable for programming the gauge.		
		
		
Selection of best generic ID for ROM based devices like bq274xx		
		
		
Device / Family #1		
Generic Chem ID	Device/ Voltage/ Chemistry	max DOD error, %
312	bq27421-G1B: 4.3V LiCoO2	100
354	bq27411-G1C: 4.35V LiCoO2	200
3142	bq27421-G1D: 4.4V LiCoO2	200
128	bq27421-G1A: 4.2V LiCoO2	200
Best generic ID 312		
Warning: Generic ID Deviation is so high that it is most likely due to anomaly in the data. Please check that data files have recomended format, units and test schedule		
		
		
Device / Family #2		
Generic Chem ID	Device/ Voltage/ Chemistry	max DOD error, %
1210	bq27621:  (ALT_CHEM1) 4.3V LiCoO2	100
354	bq27621:  (ALT_CHEM2) 4.35V LiCoO2	200
1202	bq27621: (default) 4.2V LiCoO2	200
Best generic ID 1210		
Warning: Generic ID Deviation is so high that it is most likely due to anomaly in the data. Please check that data files have recomended format, units and test schedule		
		
		
Device / Family #3		
Generic Chem ID	Device/ Voltage/ Chemistry	max DOD error, %
3230	bq27426: (default) 4.35V LiCoO2	100
3142	bq27426: (ALT-CHEM2) 4.4V LiCoO2	200
1202	bq27426: (ALT_CHEM1) 4.2V LiCoO2	200
Best generic ID 3230		
Warning: Generic ID Deviation is so high that it is most likely due to anomaly in the data. Please check that data files have recomended format, units and test schedule		
		
		

Hi Wyatt,

Thanks for your answer. I would like to clarify how critical the temperature is in the impedance tracking algorithm or CEDV technology. For example, If the thermistor is measuring the PCB board's temperature, which ranges from 21 - 27 degree, while the battery cells's temperature range from 25 - 33 degree. And we use the 21-27 degree range together with voltage, current values to gain the chemstryID, Ra values etc. Will such a difference cause the True RC, FCC jump up and down?

I have tried to set RELAX_JUMP_OK  to 0 and RELAX_SMOOTH_OK to 1, the SOC is not jumping then, but instead it increases from 27% to 55% in less than 10 minutes, which doesn't make any differences. 

If impedance track algorithm stop working, is the gauge still able to count the coulomb? If so, please let me know the method. I don't need to update the QMAX anymore after the golden image is created, I can assume the battery will remain in the same condition all the time until it dies. I guess this is the best I can do for the products existing in the market.

Thanks,

Charles

Hello Charles,

I would not think that it could cause the jumps your seeing but it will definitely impact the accuracy.

Since it sounds like it's an issue when the gauge takes an OCV and correlates the OCV to a DOD then there's either an issue with the chemID chosen, or something in the gauge settings, like the number of series cells, voltage divider ratio programmed, calibration, etc.

The gauge will report passed charge but that is still linked with the impedance track algorithm.

Sincerely,

Wyatt Keller

Hi Wyatt,

I was tried to recalibrate the voltage and then something went wrong after that, the current always stays at -32767 mA even there is no load connected. And I cannot reprogram the chip with a golden image file, but no problem to read from/ write to the registers. The steps I did to calibrate the voltage is: 1. Write 32000 in the voltage divider 2. Measure the voltage between BAT+ and BAT- 3. Go to voltage calibration and write the voltage under applied voltage. Anything wrong with my steps? 

Then I replaced the BQ34Z100 chip, I found another abnormal phenomenon on EVM board, the LED0 - LED9 were flashing once a while, maybe every half minute. Even sometimes they all went off, only the LED0 lights up. If I connected the charger, they blink every second. There is no problem to read/write or load the golden image file, and everything else seems normal. What could be wrong on the board? Have you seen this before? 

Thanks.

Charles

Hi Wyatt,

I was following the steps on page 50 of BQ34Z100-G1 datasheet. The voltage divider updates to around 37000 mV after I input the actual voltage value in the voltage calibration box, which seems correct. 

I think the LEDs flashing is due to voltage drop on REGIN from time to time. I am not quite sure what causes that, but I will replace two shift registers SN74HC164PW to see if they are pulling down the voltage to ground level once a while.