# Discrepancies in OCV-SOC Curves: Comparing Full-Cell Discharge Method vs. Electrode OCP Reconstruction

**URL:** <https://pybamm.discourse.group/t/discrepancies-in-ocv-soc-curves-comparing-full-cell-discharge-method-vs-electrode-ocp-reconstruction/325>\
**Category:** Models\
**Created:** [14 May 2025 12:17 UTC](https://pybamm.discourse.group/t/discrepancies-in-ocv-soc-curves-comparing-full-cell-discharge-method-vs-electrode-ocp-reconstruction/325 "2025-05-14T12:17:26Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![pkalbhor](https://yyz2.discourse-cdn.com/free1/user_avatar/pybamm.discourse.group/pkalbhor/32/18_2.png) [@pkalbhor](https://pybamm.discourse.group/u/pkalbhor)\
**Post date:** [14 May 2025 12:17 UTC](https://pybamm.discourse.group/t/discrepancies-in-ocv-soc-curves-comparing-full-cell-discharge-method-vs-electrode-ocp-reconstruction/325/1 "2025-05-14T12:17:26Z")

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I am calculating OCV-SOV curve for full cell from two different methods

1. Using slow discharge expriment
2. Using OCP curves of each electrodes  
Both are very different as shown in below image.  
 ![image](https://global.discourse-cdn.com/free1/uploads/pybamm/original/1X/e9e95f0b9f9dd85f7cc7f45ce8b31b3ed45cb62f.png)

What am I missing here?

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<div class="post-metadata">

**Author:** ![pkalbhor](https://yyz2.discourse-cdn.com/free1/user_avatar/pybamm.discourse.group/pkalbhor/32/18_2.png) [@pkalbhor](https://pybamm.discourse.group/u/pkalbhor)\
**Post date:** [14 May 2025 12:21 UTC](https://pybamm.discourse.group/t/discrepancies-in-ocv-soc-curves-comparing-full-cell-discharge-method-vs-electrode-ocp-reconstruction/325/2 "2025-05-14T12:21:07Z")

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Blue one in above image is calculated from simulation on full cell (with `OKane2022`)

```python
    experiment = pybamm.Experiment(
        [
            (
            "Rest for 15 minutes",
            "Discharge at 0.005C until 2.5V",
            "Rest for 15 minutes",
            ),
        ],
        period="60 seconds",
    )

```

Plotted `Bulk open-circuit voltage [V]`  
Red one is obtained by reconstructing OCV from half cell OCP curves. Example snippet

```python
    params = pybamm.ParameterValues("OKane2022")
    negative_ocp = params["Negative electrode OCP [V]"]
    positive_ocp = params["Positive electrode OCP [V]"]
    x0, x100, y100, y0 = pybamm.lithium_ion.get_min_max_stoichiometries(parameter_values=params)
    
    # Generate the data
    soc_values = [(x - x0)/(x100 - x0) for x in np.linspace(x0, x100, 100)] # SoC values from 0 to 1
    ratio = (y0 - y100) / (x100 - x0)
    y = lambda x: y0 - (ratio * (x - x0))
    # Calculate OCV values
    # OCV = positive_ocp(y(x)) - negative_ocp(x)
    ocv_values = [
        positive_ocp(y(x)) - negative_ocp(x).evaluate()[0][0] 
        for x in soc_values
        ]

```

@DrSOKane

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<div class="post-metadata">

**Author:** ![DrSOKane](https://avatars.discourse-cdn.com/v4/letter/d/b5a626/32.png) [@DrSOKane](https://pybamm.discourse.group/u/DrSOKane)\
**Post date:** [17 May 2025 11:51 UTC](https://pybamm.discourse.group/t/discrepancies-in-ocv-soc-curves-comparing-full-cell-discharge-method-vs-electrode-ocp-reconstruction/325/3 "2025-05-17T11:51:21Z")

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Hi Pritam, the best way of diagnosing what’s wrong is to print x0, x100, y100 and y0, then compare the values with those in the O’Kane 2022 paper.

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<div class="post-metadata">

**Author:** ![Sanchi](https://avatars.discourse-cdn.com/v4/letter/s/ed8c4c/32.png) [@Sanchi](https://pybamm.discourse.group/u/Sanchi)\
**Post date:** [18 August 2025 16:14 UTC](https://pybamm.discourse.group/t/discrepancies-in-ocv-soc-curves-comparing-full-cell-discharge-method-vs-electrode-ocp-reconstruction/325/4 "2025-08-18T16:14:37Z")

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Hi Pritam,

I am facing the same issue. I also tried to find other stoichiometry parameters and run with it. It didn’t help me much. Could you please help me with this issue?

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<div class="post-metadata">

**Author:** ![Notslytherin](https://avatars.discourse-cdn.com/v4/letter/n/b487fb/32.png) [@Notslytherin](https://pybamm.discourse.group/u/Notslytherin)\
**Post date:** [5 March 2026 13:31 UTC](https://pybamm.discourse.group/t/discrepancies-in-ocv-soc-curves-comparing-full-cell-discharge-method-vs-electrode-ocp-reconstruction/325/5 "2026-03-05T13:31:40Z")

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Hi pkalbhor,

Have you fixed this issue?