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[ONGOING DRAFT - VERIFY INFO]

Objective:

  • To choose a module prototype to move forward with. [NOT PRODUCTION LEVEL TESTING]

    • Thermal Performance: Is the module easy to cool? Are there risks of a thermal runaway?

    • Electrical Performance: Does the module work? Are there areas with extremely high current density? IR? High Resistance?

    • Realize that we are pushing the module to its limits… The standard test conditions are listed below.

Context:

  • put our packs/modules/cells through <100 cycles

  • “The major effects (sudden capacity loss) are most likely to appear after 100 cycles of the pack, however, minor effects will always be present” [2]

  • our pack will be assembled for 1-2 months

Background Information:

OEM Specs:

It is important to inform our test procedure from the OEM specs for the cells we are planning to use:

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The module will be subjected to varying cycling patterns in various environmental condiyionsconditions. It should be easy to cool and safe from thermal runaway, melting, shorts, etc.

Procedure:

Software Setup (Skip) - use Python 3.10

  1. Install (follow their respective instructions closely)

2. Set up development requirement

  • Create a python venv or anaconda environment

  • Install libraries according to requirements.txt

  1. DAQ (thermistor data)

  • Code Block
    git clone https://github.com/kostubhagarwal/module_test_data_acquisition.git

Hardware Setup (Verify) - [Discharge Only]

  1. Plug in Keysight N7000 series power supply

  2. Wire the A2D 64 channel PCB into the Keysight DAQ970A 

  3. Plug the power supply into Attach/calibrate thermistors to A2D 64-CH DAQ and to corresponding locations on the module

  4. Power on the B&K Precision 8600 E-load

  5. Connect your PC to the DAQ and the B&K Precision 8600 E-load to your laptop

Test Setup 

  1. Close wind-tunnel 

  2. Power on PowerSupply, DAQ, and E-Loadthe B&K Precision 8600 E-load

  3. Connect the battery module terminals to the E-load[make sure polarity is correct]

  4. Connect the A2D 64-channel PCB to your laptop

Testing

  1. navigate to /battery_testing/Test_Equipment_Control and run the following command in the terminal

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  1. name the test: msxv_prototype_test (can import test going forward)

  2. select CC_Discharge_Only

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3. select the following settings: [Charging - Not Applicable]

16.8V: 4.2V * 4, end-voltage
11.6A: 1.45A/cell*8, current
0.4A: end-current
15 Minutes: rest
10V: 2.5Vx4, end voltage
12A60A: 8x18x7.5A, discharge current
20 Minutes: rest
1s: measurement interval

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5. do you want to do a storage charge: yes

6. would you like to import new settings for charge only cycle

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7. Click start test

We will charge and discharge each module, assuming that the modules have the same capacity and are at the same voltage.

During the entire test, log the voltage, current, and temperature for each cell. Multimeters to log single cell voltages (XXs interval (fast as possible)), and DAQ module to measure the thermistors (5s interval).

Storage Charge [Very important, however, must be done manually]

  1. Storage Charge + Inspection

    1. Charge so that each cell is approximately at the nominal voltage (~3.6V), and the module is at (~4*3.6=14.4V). This ensures the best SoH of modules and cells.

    2. Storage Charge to maintain cell safety

      1. 33.6V max voltage (~4.2V/cell)

      2. 5.8A CC portion

      3. 25A end Current

        1. We don’t want the storage to take a ton of time - we don’t need to wait for the current to drop all the way - voltage will sag a bit after finishing the charge, but we have increased the voltage to 3.8V/cell instead of the standard 3.7V/cell to account for this.

    3. After the above procedure is followed, we will calculate the capacity of each of the parallel groups to ensure there are no major discrepancies. Any voltage limits that were exceeded or not hit correctly, we will be able to create a model of the LG M50 cells and use that to extrapolate the data to get a full-capacity measurement. We will also examine the temperature graphs and the IC/DV graphs to ensure the uniformity of the cells.

References:

[1] The Fundamentals of Battery/Module Pack Test (nhresearch.com)

[2] lithium Battery testing Procedures - YouTube

Bibliography

Links:

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