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Original question:

CCS/BQ27510-G3: BQ27510-G3

CCS/BQ27510-G3: BQ27510-G3

Emma Wang(DELL EMC)
Intellectual 350 points
Part Number: BQ27510-G3

Tool/software: Code Composer Studio

1,Application is like that board with battery is in system for 5 years. Battery will charge to 4.2V(100%). Then there is an leakage current 10mA to discharge battery to 95%(4.1V) with 2days. And battery will charge it again to full. Discharge current threshold is 100mA. My problem is how to know battery real capacity (or SOH) during this period? Can unfiltered RM, unfiltered FCC and truesoc indicate real capacity of battery?

2, If Battery will charge to 4.2V(100%). Then there is an leakage current 10mA to discharge battery to low soc. Can this process update Ra table and Qmax?

3,Because our leakage current is about 10mA. If I set dsg current threshold below to 10mA, can Ra table and Qmax update and be accurate?

4,As SLUA450 states 'In order to ensure high accuracy of the DOD measurement, the Qmax calculation does not occur if the temperature is above 40°C, or below 10°C.' But in our application, battery temp is about 60C normally. Could you modify temperature threshold allowed to update Qmax? How? This temperature is the reading 'temperature parameter' of FG, is it right? (cell is INR18650A from Moli)

5, As you said 'if you have completed your golden learning cycle, then you need just 37% of design capacity passed charge for qmax to update.' Could I modify threshold of 37% to 5% for Qmax update? Will it be accurate?

6,There are two groups of Ra table and Qmax 0 and 1. Once FG choose group 0 for battery at the beginning. Is it possible for this battery to change to use group 1 during its 5 service years?

7,Even if I can update Ra during service time, it just updates 'Ra0 table' and other 5 tables are same with original data. So I think it is useless for RM,FCC's accuracy. Because FG may still use Ra table that didn't update. Is it right?

8,Do Ra0, Ra0x and Ra0 default tables(or Ra1, Ra1x and Ra1 default tables ) update during discharge when this FW completed learning cycle? How do you make sure FG still use updated Ra instead of Ra without update?

9,What method does FG use to choose which Ra table to use?

10,Please according to your experience and calculation method, tell me a deviation between unfiltered RM and actual unfiltered RM after 2 years(2 times of original impedance)?

Thanks!

  • 0
    TI__Mastermind 24870 points
    1. RemCap is just a prediction. We have an applications note on how to calculate RM or SOC accuracy.

    2. Refer to the TRM. We have a setting "Quit Current". Depending on the 10 mA leakage corresponding to your entire cell capacity (C-rate), it will not update impedance below C/10 by default.

    3. I don't think so if it is below C/10. The battery itself has a rate-limited dependence for impedance. We may learn larger values vs your actual discharge impedance.

    4. What is the maximum temperature? 60 degrees C or higher? Can you send over a senc file?

    5. I don't recommend this. Our algorithm needs 37% to be accurate. We've tested on smaller samples sizes and it required significant modifications that assumed fixed cycles.

    6. That's meant for swapping packs. If your battery stays with the gauge, it should not swap tables or Qmax values.

    7. It depends on the flags. 0x55 means the table that's currently being used. (Ra Flags). 0x00 means it's updated but not used.

    8. The fuel gauge handles this automatically. (see 7)

    9. Depends on the flag settings.

    10. It really depends. Based on what I've observed, if we got valid Qmax updates during your system operation and Ra updates, you will see less unpredictable SOC behavior. However, if there's leakage current we don't account for, Ra values may be learned abnormally large or small and we may not get Qmax updates. We have filters in place, but it still occurs on select units that may have been exposed to high temperatures or high currents.
  • 0 in reply to Kang Kang
    Intellectual 350 points

    1, Background: Application is like that board with battery is in system for 5 years. Battery will charge to 4.2V(100%). Then there is an leakage current 10mA to discharge battery to 95%(4.1V) with 2days. And battery will charge it again to full. Discharge current threshold is 100mA. Quit current is 15mA. Impedance of cell will become twice of original after 2years. Cell is Moli INR18650A.

     Question: Do unfiltered RM and SOH reflect real battery capacity over 5 years? If not, how to make unfiltered RM reflect real capacity? Do I have to discharge like once or twice a year to get accurate unfiltered RM?  

    2,Maximum battery temperature is 67C. And battery temp is over 40C in most case. How can I modify 40C threshold?

    2022.V04.zip

    3,OK, FG handle whihc one to use automatically. But can it make sure it always use the newest updated one? Because in our normal application, there is no Ra and Qmax update. I am thinking to introduce discharge process periodically like discharge to 50% with 600mA twice a year. The question is i must make sure FG is using the newest updated one, otherwise unfiltered RM accuracy is not good.

    4,Based on background of 1, Could you  tell me a deviation between unfiltered RM and actual unfiltered RM after 2 years(2 times of original impedance) without Ra and Qmax update? 

    Thanks a lot!

  • 0 in reply to Emma Wang(DELL EMC)
    TI__Mastermind 24870 points
    1. They should if we go through learning cycle. This is something you have to try in your lab.

    2. Please refer to the TRM for modifying dataflash.

    3. I do think it is a good idea to let the gauge go through a learning cycle, however this will be dependent on your system. I suggest running a learning cycle to see if accuracy improves, once it does determine on your system how often you will need the learning cycle.

    4. I cannot tell, this is different system over system and cell over cell.