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BQ34Z110 optimization at less than C/10

Stuart Graham
Prodigy 165 points

Hello,

We have a large battery bank (110Ah 24V) which will see a typical load of 2.5A, max of 4A and our shunt is designed for 5A.

To run an optimisation cycle, everything says we should use C/10 which is impossible for us, a max of 5A which is C/22.

Is it possible to adjust any parameters to ensure accurate fuel gauging at these loads?

Thanks,

Stuart

  • 0
    TI__Guru 73830 points

    Stuart.

     WE do not recommend running the optimization cycle with a discharge current less than C/10. Do you have several cells in parallel? If so, can you change to a 1P configuration for the optimization cycle. We then divide the optimized Ra table by the number of parallel cells and update the table.

    Tom

  • 0 in reply to ThomasCosby
    Prodigy 165 points

    Hello,

    Yes, the battery module consists of two parallel strings of 12 cells so by taking one branch out we can discharge at C/11.

    As we would normally have settings as follows:

    CONFIG Section
    Design Cell Voltage: 2000mV

    Number of series cells: 12

    Design Cell Capacity: 11,000 (for 110Ah X10)
    Design Cell Energy: 22,000 (for 2.2kWh)

    Cell BL Set: 1833
    Cell BL Clear: 1850
    Cell BH Set: 2450
    Cell BH Clear: 2400

    GAS GAUGING Section
    Cell Terminate Voltage: 1833

    If discharging only half the bank for optimisation cycle, should we change the cell design capacity by half too and amend them once the optimisation has completed?

    So, my setup procedure would be as follows:

    1. Enter Configuration, Approx Calibration & Gas Gauging initial values
    2. Run Calibration procedure
    3. Write all 
    4. Run Optimisation Cycle as per step 8 (with reduced size battery bank and any modified settings)
    5. Read all
    6. Save data file for writing to other units

    My plan then would be to then do a single discharge/recharge cycle on each unit (we produce units in qtys of 1-10 and need to prove all batteries will hold a 24 hour load) and compare the FG readings to test.

    Reading one of the application notes, it advises to disable IT for a golden image... Surely this should be enabled to allow the production units to monitor the battery?

    Thanks for your continued help,

    Stuart

  • 0 in reply to Stuart Graham
    Prodigy 165 points

    Hi Thomas,

    Were you able to check if my understanding of the procedure was appropriate?

    I was also thinking to use the Evaluation module with a 1/2 sized battery bank as i can then discharge at around C/8 for the characterisation, then load the senc file from the evaluation module into the production module and recalibrate the current, voltage and temperatures for the new module.  This would then result in my golden image?

    Thanks,

    Stuart

  • 0 in reply to Stuart Graham
    TI__Guru 73830 points

    Stuart,

    Your process looks correct, but connecting two series strings in parallel is not a normal configuration and I am not sure that the gauge can support that. I will discuss it with our IT expert to get his opinion.

    Tom