• State Resolved
  • Locked Locked
  • Replies 3 replies
  • Subscribers 62 subscribers
  • Views 170 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

BQ35100: High Design Capacity EOS and Remaining Charge Accuracy

Thomas Hillis
Prodigy 20 points
Part Number: BQ35100
Other Parts Discussed in Thread: BQSTUDIO,

Hello,

We have a 5s6p LiSOCl2 battery pack. Each cell is 13Ah for a pack capacity of 78Ah. Two packs will be used in parallel for a capacity of 156Ah. The correct chemistry for the cell used is found in bqstudio. With such a high design capacity, will the gauge accurately detect EOS and remaining charge? If so, what register changes are required for this battery configuration?

Thanks,

Thomas

  • +1
    TI__Genius 11750 points

    Hello Thomas,

    The best way to handle this is most likely scaling. Read section 3 of this document for reference. To summarize, you could set the capacity to something like 1/6 of the actual value, and do the same with the current calibration. Doing that essentially tricks the gauge into thinking the capacity is smaller, but the algorithm should work regardless since it is roughly equivalent. The more you scale, the larger the error though, as you are losing resolution essentially. 

    The EOS algorithm should handle this scaling fine because it is based on a change in resistance. The only final concern is that you will need the learning resistance voltage drop to be significant enough for the gauge. With such a large capacity, it may take a very large amount of current to achieve that. At least 50mV - 100mV of drop should be okay for learning, but more is better. 

    Let me know if you have any other questions.

    thanks,

    Alex M.

  • 0
    Prodigy 20 points

    Hello Alex,

    Thank you for your reply. Two more questions.

    1. Is the Cell Design Capacity register in bqstudio for the bq35100 supposed to be the capacity of a single battery or the design capacity of the entire pack.

    2. Is there a way to set a parallel cell count, or just a series cell count?

  • +1 in reply to Thomas Hillis
    TI__Genius 11750 points

    Hello Thomas,

    In most of our gauges we have design capacity (mAH) and design energy (cWH). Since this gauge uses a different algorithm, it doesn't need the design energy. Design capacity increases with parallel cells and thus the register should have the capacity of the whole pack. Series cells don't actually increase the design capacity but do increase design energy. There is a register for the number of series cells but that is for the gauge to restore the scaled voltage back to the original.

    Thanks,

    Alex M.