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BQ35100: No SOH reported for CR123 (Chem_ID 0x602)

Holger Kaplan
Prodigy 20 points
Part Number: BQ35100
Other Parts Discussed in Thread: BQSTUDIO

Hello TI-Team,

I'm struggling with the SOH mode from the BQ35100. If the mode is activated, we don't get any information about the SOH of the connected primary battery. Hope you could help. For testing we take our own designed board. A electronic load is connected to the BAT+ and system GND connection. For simulation of the battery we are using a battery simulator from Keightley. Our system has got 4S CR123 battery pack, so we have set the gas gauging parameters to the following settings:

The CHEM-ID is set to 0x602 at should be the correct one for CR123 primary batteries. We did not have an external temperature resistor in our test bench, but we will take one in our final application. Therefore we use the internal temperature sensor.

The calibration is done correctly, the CC Gain and CC Delta settings are set to the corresponding shunt resistor on our board.

Q1: Which parameters are set/influenced by the calibration process? Is there a list available?

When using the BQ35100 in ACC mode ([GMSEL1:0] = 00) the coulomb counter works correct. You could see the results in the file BQ35100_WATCH_ACC_MODE, setup is BQ35100_ACC_MODE.gg.csv

For starting of the measurement, I have send the command GAUGE_START from BQStudio. The charge accumulation is increased correctly, so a HW fault could not be the problem.

Q2: As I understand, the SOH is only reported in SOH and EOS, not in ACC mode. the measured Z and Scaled R parameters are only non zero, when we are in EOS mode. Is this correct?

BQ35100_ACC_MODE.gg.csv

BQ35100_WATCH_ACC_MODE.log 
Data Log

TimeStamp,Control,Charge Accumulation,Temperature,Voltage,Battery Status,Battery Alert,Current,Measured Z,Scaled R,Internal Temperature,SOH,Design Capacity
2021-08-06 10:35:30.273,0x2081,0,25.7,12008,0x0001,0x0001,0,0,0,25.6,0,1500
2021-08-06 10:35:32.279,0x2081,0,25.6,12004,0x0001,0x0001,0,0,0,25.6,0,1500
2021-08-06 10:35:34.288,0x2081,0,25.6,11994,0x0001,0x0001,0,0,0,25.6,0,1500
2021-08-06 10:35:36.306,0x2081,0,25.6,11998,0x0001,0x0001,0,0,0,25.6,0,1500
2021-08-06 10:35:38.296,0x2081,0,25.6,12004,0x0001,0x0001,0,0,0,25.6,0,1500
2021-08-06 10:35:40.299,0x2081,0,25.6,11996,0x0001,0x0001,0,0,0,25.6,0,1500
2021-08-06 10:35:42.301,0x2081,0,25.6,12002,0x0001,0x0001,0,0,0,25.6,0,1500
2021-08-06 10:35:44.366,0x2081,0,25.6,12005,0x0001,0x0001,0,0,0,25.6,0,1500
2021-08-06 10:35:46.313,0x2081,0,25.5,11991,0x0001,0x0001,0,0,0,25.6,0,1500
2021-08-06 10:35:48.325,0x2081,0,25.5,12001,0x0001,0x0001,0,0,0,25.6,0,1500
2021-08-06 10:35:50.328,0x2081,0,25.5,12009,0x0001,0x0001,0,0,0,25.5,0,1500
2021-08-06 10:35:52.331,0x2081,0,25.5,11987,0x0001,0x0001,0,0,0,25.5,0,1500
2021-08-06 10:35:54.333,0x2081,0,25.5,10256,0x0001,0x0001,0,0,0,25.5,0,1500
2021-08-06 10:35:56.334,0x2081,-500,25.5,10250,0x0001,0x0001,-1000,0,0,25.6,0,1500
2021-08-06 10:35:58.336,0x2081,-1054,25.6,10236,0x0001,0x0001,-1000,0,0,25.6,0,1500
2021-08-06 10:36:00.337,0x2081,-1609,25.6,10234,0x0001,0x0001,-1000,0,0,25.6,0,1500
2021-08-06 10:36:02.338,0x2081,-2166,25.6,10221,0x0001,0x0001,-1000,0,0,25.6,0,1500
2021-08-06 10:36:04.353,0x2081,-2720,25.7,10215,0x0001,0x0001,-1000,0,0,25.7,0,1500
2021-08-06 10:36:06.342,0x2081,-3277,25.7,10209,0x0001,0x0001,-1000,0,0,25.7,0,1500
2021-08-06 10:36:08.370,0x2081,-3832,25.7,10197,0x0001,0x0001,-1000,0,0,25.7,0,1500
2021-08-06 10:36:10.351,0x2081,-4386,25.7,10197,0x0001,0x0001,-1000,0,0,25.7,0,1500
2021-08-06 10:36:12.386,0x2081,-4943,25.7,10177,0x0001,0x0001,-1000,0,0,25.7,0,1500
2021-08-06 10:36:14.369,0x2081,-5498,25.7,10175,0x0001,0x0001,-1000,0,0,25.7,0,1500
2021-08-06 10:36:16.402,0x2081,-6054,25.8,10169,0x0001,0x0001,-1000,0,0,25.8,0,1500
2021-08-06 10:36:18.399,0x2081,-6609,25.7,10159,0x0001,0x0001,-1000,0,0,25.8,0,1500
2021-08-06 10:36:20.403,0x2081,-7164,25.8,10149,0x0001,0x0001,-1000,0,0,25.8,0,1500
2021-08-06 10:36:22.407,0x2081,-7720,25.8,10144,0x0001,0x0001,-1000,0,0,25.8,0,1500
2021-08-06 10:36:24.418,0x2081,-8275,25.8,10136,0x0001,0x0001,-1000,0,0,25.8,0,1500
2021-08-06 10:36:26.423,0x2081,-8832,25.8,10120,0x0001,0x0001,-1000,0,0,25.8,0,1500
2021-08-06 10:36:28.427,0x2081,-9300,25.8,10476,0x0001,0x0001,-800,0,0,25.8,0,1500
2021-08-06 10:36:30.434,0x2081,-9744,25.8,10465,0x0001,0x0001,-800,0,0,25.8,0,1500
2021-08-06 10:36:32.440,0x2081,-10189,25.8,10465,0x0001,0x0001,-800,0,0,25.8,0,1500
2021-08-06 10:36:34.443,0x2081,-10632,25.8,10454,0x0001,0x0001,-800,0,0,25.8,0,1500
2021-08-06 10:36:36.447,0x2081,-11078,25.8,10449,0x0001,0x0001,-800,0,0,25.8,0,1500
2021-08-06 10:36:38.451,0x2081,-11521,25.8,10431,0x0001,0x0001,-800,0,0,25.8,0,1500
2021-08-06 10:36:40.465,0x2081,-11966,25.8,10431,0x0001,0x0001,-800,0,0,25.8,0,1500
2021-08-06 10:36:42.473,0x2081,-12410,25.8,10433,0x0001,0x0001,-800,0,0,25.8,0,1500
2021-08-06 10:36:44.476,0x2081,-12855,25.8,10426,0x0001,0x0001,-800,0,0,25.8,0,1500
2021-08-06 10:36:46.489,0x2081,-13298,25.8,10405,0x0001,0x0001,-800,0,0,25.8,0,1500
2021-08-06 10:36:48.493,0x2081,-13744,25.8,10409,0x0001,0x0001,-800,0,0,25.8,0,1500
2021-08-06 10:36:50.505,0x2081,-14187,25.8,10579,0x0001,0x0001,-800,0,0,25.8,0,1500
2021-08-06 10:36:52.506,0x2081,-14632,25.8,10573,0x0001,0x0001,-800,0,0,25.7,0,1500
2021-08-06 10:36:54.511,0x2081,-15076,25.8,10571,0x0001,0x0001,-800,0,0,25.8,0,1500
2021-08-06 10:36:56.518,0x2081,-15521,25.8,10563,0x0001,0x0001,-800,0,0,25.8,0,1500

I we configure the BQ35100 to SOH mode we did not get the SOH reported. Also the Charge accumulation as well the current is not reported anymore, as you can see in the log file. The gg file isa attached as well.

Workflow for changing to SOH mode.

  1. 1Set SOH mode ([GMSEL1:0] = 01)
  2. RESET BQ35100 via RESET button in BQStudio
  3. Send a new battery command (is this necessary? It is not possible to send via Button, must be done in Advanced mode)
  4. Begin gauging with GAUGE_START command with attached load

Please see attached files. We could not see any current and charge accumulation change. The SOH stays always on 98% (Battery simulator shows a decreasing SOH)

Q3: What is wrong in this setting? The CHEM-ID should match to the battery connected. Which values should be updated in SOH mode? In my opinion there is something generally wrong, as we even did not see a current change. The voltage is reported correct.

Q4: Which parameters are influenced by the CHEM_ID?

Q5: As I understand, the Ra table represents the ESR of the battery in different SOH situations. We use a 4S primary battery topology. Is this calculated by the BQ35100 itself (ESR*4?)

Q6: In another device we use a L91 primary battery, which fits to the chem id 0601. As the datasheet mentions, the SOH mode is for Li-MnO2, the EOS for Li-SOCl2. Could we only use the ACC mode therefore?

BR for a quick responseBQ35100_SOH_MODE.gg.csv

BQ35100_WATCH_SOH_MODE.log 
Data Log

TimeStamp,Control,Charge Accumulation,Temperature,Voltage,Battery Status,Battery Alert,Current,Measured Z,Scaled R,Internal Temperature,SOH,Design Capacity
2021-08-06 10:53:38.669,0x2080,0,25.9,10308,0x0001,0x0001,0,0,0,25.9,98,1500
2021-08-06 10:53:40.679,0x2080,0,25.9,10308,0x0001,0x0001,0,0,0,25.9,98,1500
2021-08-06 10:53:42.694,0x2080,0,25.9,10308,0x0001,0x0001,0,0,0,25.9,98,1500
2021-08-06 10:53:44.699,0x2080,0,25.9,10308,0x0001,0x0001,0,0,0,25.9,98,1500
2021-08-06 10:53:46.701,0x2080,0,25.9,10308,0x0001,0x0001,0,0,0,25.9,98,1500
2021-08-06 10:53:48.717,0x2080,0,25.9,10308,0x0001,0x0001,0,0,0,25.9,98,1500
2021-08-06 10:53:50.718,0x2080,0,25.9,10308,0x0001,0x0001,0,0,0,25.9,98,1500
2021-08-06 10:53:52.722,0x2080,0,25.9,10308,0x0001,0x0001,0,0,0,25.9,98,1500
2021-08-06 10:53:54.725,0x2080,0,25.9,10308,0x0001,0x0001,0,0,0,25.9,98,1500
2021-08-06 10:53:56.726,0x2080,0,25.9,10308,0x0001,0x0001,0,0,0,25.9,98,1500

  • 0
    TI__Intellectual 2146 points

    Hi Holger,

    I will get back to you tomorrow on this issue.

  • 0 in reply to Albert Anwar
    TI__Intellectual 2146 points

    Holger,

    1. The parameters set in the calibration is in the Calibration class of parameters. In particular the parameters offset include CC Offset, Board Offset, Internal Temperature Offset, External Temperature Offset, and Pack V Offset.

    2. You are correct about SOH being relevant only in SOH and EOS mode. The MeasuredZ and ScaledR parameters don't get updated when not in EOS mode, so you don't need to worry about those if the gauge is not in this mode.

    3. SOH mode does not use current information to determine SOH. The device will take voltage and temperature measurements to update the SOH when the GE pin gets toggled.

    4. Lots of parameters get updated, including the Ra table, although I don't have a comprehensive list at this time. Getting the Chem ID correct is extremely important for the correct operation of the gauge though, so you'll want to ensure that this is correct.

    5. I believe the gauge does take the cell count into account, although I'm not completely certain. I can get a more definitive answer for you later if you'd like.

    6. Yes, you will need to use ACC mode for this battery.

  • 0
    Prodigy 20 points

    Hello Albert, sorry for the late reply. As I understand, we could only measure the battery in SOH mode, when we have a correct temperature information from the battery, am I right? So, when we don't have the possibility to take a external temperature sensor or the internal temperature is not close to the battery, the SOH mode does not make any sense.

    Also I have made other test with my development board to see the influence of toggling the GE pin. Everytime toggling the GE pin, the SOH falls in 10% steps, which is definitely not correct. Could this be caused by the wrong temeprature information?

  • 0 in reply to Holger Kaplan
    TI__Intellectual 2146 points

    Holger,

    That's correct, you'll need temperature to be accurate for the SOH value to be correct. It's possible that wrong temperature readings are causing what you're seeing.

  • 0 in reply to Albert Anwar
    Prodigy 20 points

    Hello Albert,

    as conclusion, if we have got a handheld, which is in a rough temperature environment and the temperature sensor could not be suited directly to the secondary battery pack, you will suggest using the ACC mode for a chemicals?

    BR Holger

  • +1 in reply to Holger Kaplan
    TI__Genius 11535 points

    Hi Holger,

    I apologize for the delay. Yes I would suggest ACC mode.

    Best,

    Jessica