From 2902baee299e387e944f490d4b4bfeef6a9dd376 Mon Sep 17 00:00:00 2001
From: Mark Campanelli <mark.campanelli@gmail.com>
Date: Fri, 1 Dec 2023 09:57:06 -0700
Subject: [PATCH 01/14] Minimal functionality for early feedback

---
 pvlib/pvsystem.py            | 57 ++++++++++++++++++++++++++++++++++++
 pvlib/tests/test_pvsystem.py | 45 ++++++++++++++++++++++++++++
 2 files changed, 102 insertions(+)

diff --git a/pvlib/pvsystem.py b/pvlib/pvsystem.py
index f0c1cd2cda..3aeaf7d241 100644
--- a/pvlib/pvsystem.py
+++ b/pvlib/pvsystem.py
@@ -7,11 +7,13 @@
 import functools
 import io
 import itertools
+import numbers
 import os
 import inspect
 from urllib.request import urlopen
 import numpy as np
 from scipy import constants
+import scipy.optimize
 import pandas as pd
 from dataclasses import dataclass
 from abc import ABC, abstractmethod
@@ -3022,3 +3024,58 @@ def combine_loss_factors(index, *losses, fill_method='ffill'):
         combined_factor *= (1 - loss)
 
     return 1 - combined_factor
+
+
+def _negative_total_power(current, *args):
+    """
+    Compute negative of total power generated by devices in series at specified current.
+    """
+    return -np.sum(current * v_from_i(current, *args))
+
+
+def max_power_point_mismatched(
+        photocurrent, saturation_current, resistance_series, resistance_shunt, nNsVth,
+):
+    """Compute maximum power info for (possibly) mismatched set of devices in series."""
+    if all([isinstance(input, numbers.Number) for input in (
+       photocurrent, saturation_current, resistance_series, resistance_shunt, nNsVth 
+    )]):
+        # There cannot be mismatch, so fall back to non-mismatch function.
+        return {
+            **max_power_point(
+                photocurrent,
+                saturation_current,
+                resistance_series,
+                resistance_shunt,
+                nNsVth
+            )
+        }
+
+    i_mp_0 = max_power_point(
+        np.mean(photocurrent),
+        np.mean(saturation_current),
+        np.mean(resistance_series),
+        np.mean(resistance_shunt),
+        np.mean(nNsVth),
+    )["i_mp"]
+    args = photocurrent, saturation_current, resistance_series, resistance_shunt, nNsVth
+    sol = scipy.optimize.minimize(_negative_total_power, i_mp_0, args)
+
+    if sol.success:
+        i_mp = sol.x[0]
+        v_mp = v_from_i(
+            i_mp,
+            photocurrent,
+            saturation_current,
+            resistance_series,
+            resistance_shunt,
+            nNsVth,
+        )
+
+        return {
+            "i_mp": i_mp,
+            "v_mp": v_mp,
+            "p_mp": i_mp * v_mp,
+        }
+
+    raise RuntimeError(f"unsuccessful solution: {sol}")
diff --git a/pvlib/tests/test_pvsystem.py b/pvlib/tests/test_pvsystem.py
index 6557d77e10..d60abe161f 100644
--- a/pvlib/tests/test_pvsystem.py
+++ b/pvlib/tests/test_pvsystem.py
@@ -4,6 +4,7 @@
 import numpy as np
 from numpy import nan, array
 import pandas as pd
+import scipy.constants
 
 import pytest
 from .conftest import (
@@ -2549,3 +2550,47 @@ def test_Array_temperature_missing_parameters(model, keys):
         array.temperature_model_parameters = params
         with pytest.raises(KeyError, match=match):
             array.get_cell_temperature(irrads, temps, winds, model)
+
+
+@pytest.mark.parametrize(
+    'inputs', 
+    [
+        {
+            "photocurrent": 6.2,
+            "saturation_current": 1.0e-8,
+            "n": 1.1,
+            "resistance_series": 0.0001,
+            "resistance_shunt": 5000.0,
+            "Ns": 60,
+            "T": 25.0,
+        },
+        {
+            "photocurrent": np.array([5.8, 6.2]),
+            "saturation_current": 1.0e-8,
+            "n": 1.1,
+            "resistance_series": 0.0001,
+            "resistance_shunt": 5000.0,
+            "Ns": 60,
+            "T": 25.0,
+        }
+    ]
+)
+def test_max_power_point_mismatched(inputs):
+    """Test max power point computaiton for mismatched devices in series."""
+
+    photocurrent = inputs["photocurrent"]
+    saturation_current = inputs["saturation_current"]
+    resistance_series = inputs["resistance_series"]
+    resistance_shunt = inputs["resistance_shunt"]
+    q_C = scipy.constants.value("elementary charge")
+    k_B_J_per_K = scipy.constants.value("Boltzmann constant")
+    T_K = scipy.constants.convert_temperature(inputs["T"], "Celsius", "Kelvin")
+    nNsVth = inputs["n"] * inputs["Ns"] * k_B_J_per_K * T_K / q_C
+
+    pvsystem.max_power_point_mismatched(
+        photocurrent,
+        saturation_current,
+        resistance_series,
+        resistance_shunt,
+        nNsVth,
+    )

From 1c2404a8a84a9cc3e6683ba454c4cf42ed083507 Mon Sep 17 00:00:00 2001
From: Mark Campanelli <mark.campanelli@gmail.com>
Date: Fri, 1 Dec 2023 10:15:38 -0700
Subject: [PATCH 02/14] Appease flake8

---
 pvlib/pvsystem.py | 36 +++++++++++++++++++++++++++++-------
 1 file changed, 29 insertions(+), 7 deletions(-)

diff --git a/pvlib/pvsystem.py b/pvlib/pvsystem.py
index 3aeaf7d241..920e9beb60 100644
--- a/pvlib/pvsystem.py
+++ b/pvlib/pvsystem.py
@@ -3028,18 +3028,34 @@ def combine_loss_factors(index, *losses, fill_method='ffill'):
 
 def _negative_total_power(current, *args):
     """
-    Compute negative of total power generated by devices in series at specified current.
+    Compute negative of total power generated by devices in series at
+    specified current.
     """
     return -np.sum(current * v_from_i(current, *args))
 
 
 def max_power_point_mismatched(
-        photocurrent, saturation_current, resistance_series, resistance_shunt, nNsVth,
+    photocurrent,
+    saturation_current,
+    resistance_series,
+    resistance_shunt,
+    nNsVth,
 ):
-    """Compute maximum power info for (possibly) mismatched set of devices in series."""
-    if all([isinstance(input, numbers.Number) for input in (
-       photocurrent, saturation_current, resistance_series, resistance_shunt, nNsVth 
-    )]):
+    """
+    Compute maximum power info for (possibly) mismatched set of devices in
+    series.
+    """
+    if all(
+        [
+            isinstance(input, numbers.Number) for input in (
+                photocurrent,
+                saturation_current,
+                resistance_series,
+                resistance_shunt,
+                nNsVth,
+            )
+        ]
+    ):
         # There cannot be mismatch, so fall back to non-mismatch function.
         return {
             **max_power_point(
@@ -3058,7 +3074,13 @@ def max_power_point_mismatched(
         np.mean(resistance_shunt),
         np.mean(nNsVth),
     )["i_mp"]
-    args = photocurrent, saturation_current, resistance_series, resistance_shunt, nNsVth
+    args = (
+        photocurrent,
+        saturation_current,
+        resistance_series,
+        resistance_shunt,
+        nNsVth,
+    )
     sol = scipy.optimize.minimize(_negative_total_power, i_mp_0, args)
 
     if sol.success:

From 4859d64fcba7763afaa84e62981ce2399619f4e2 Mon Sep 17 00:00:00 2001
From: Mark Campanelli <mark.campanelli@gmail.com>
Date: Fri, 1 Dec 2023 10:28:10 -0700
Subject: [PATCH 03/14] Appease flake8 more

---
 pvlib/tests/test_pvsystem.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pvlib/tests/test_pvsystem.py b/pvlib/tests/test_pvsystem.py
index d60abe161f..4f007f3e4b 100644
--- a/pvlib/tests/test_pvsystem.py
+++ b/pvlib/tests/test_pvsystem.py
@@ -2553,7 +2553,7 @@ def test_Array_temperature_missing_parameters(model, keys):
 
 
 @pytest.mark.parametrize(
-    'inputs', 
+    'inputs',
     [
         {
             "photocurrent": 6.2,

From e881ce7f7934eb2ca2d606be93dba5dc27bee837 Mon Sep 17 00:00:00 2001
From: Mark Campanelli <mark.campanelli@gmail.com>
Date: Fri, 1 Dec 2023 11:33:22 -0700
Subject: [PATCH 04/14] Improve solver, streamline,  and add tests

---
 pvlib/pvsystem.py            | 67 ++++++++++++++++++----------------
 pvlib/tests/test_pvsystem.py | 70 +++++++++++++++++++++++++++++++-----
 2 files changed, 98 insertions(+), 39 deletions(-)

diff --git a/pvlib/pvsystem.py b/pvlib/pvsystem.py
index 920e9beb60..f7f3d889e0 100644
--- a/pvlib/pvsystem.py
+++ b/pvlib/pvsystem.py
@@ -3040,40 +3040,29 @@ def max_power_point_mismatched(
     resistance_series,
     resistance_shunt,
     nNsVth,
+    *,
+    i_mp_ic=None,
 ):
     """
     Compute maximum power info for (possibly) mismatched set of devices in
-    series.
+    series. When using this serially on time-series data, passing i_mp_ic from
+    previous step may speed up computation. Algorithm falls back to automated
+    computation of i_mp_ic if solution fails with provided i_mp_ic. The value
+    of i_mp_ic used is returned along with i_mp (same value for all devices),
+    v_mp, and p_mp.
     """
-    if all(
-        [
-            isinstance(input, numbers.Number) for input in (
-                photocurrent,
-                saturation_current,
-                resistance_series,
-                resistance_shunt,
-                nNsVth,
-            )
-        ]
-    ):
-        # There cannot be mismatch, so fall back to non-mismatch function.
-        return {
-            **max_power_point(
-                photocurrent,
-                saturation_current,
-                resistance_series,
-                resistance_shunt,
-                nNsVth
-            )
-        }
+    if i_mp_ic is None:
+        i_mp_ic = max_power_point(
+            np.mean(photocurrent),
+            np.mean(saturation_current),
+            np.mean(resistance_series),
+            np.mean(resistance_shunt),
+            np.mean(nNsVth),
+        )["i_mp"]
+        retry_ic = False
+    else:
+        retry_ic = True
 
-    i_mp_0 = max_power_point(
-        np.mean(photocurrent),
-        np.mean(saturation_current),
-        np.mean(resistance_series),
-        np.mean(resistance_shunt),
-        np.mean(nNsVth),
-    )["i_mp"]
     args = (
         photocurrent,
         saturation_current,
@@ -3081,7 +3070,9 @@ def max_power_point_mismatched(
         resistance_shunt,
         nNsVth,
     )
-    sol = scipy.optimize.minimize(_negative_total_power, i_mp_0, args)
+    sol = scipy.optimize.minimize(
+        _negative_total_power, i_mp_ic, args=args, jac='3-point'
+    )
 
     if sol.success:
         i_mp = sol.x[0]
@@ -3095,9 +3086,25 @@ def max_power_point_mismatched(
         )
 
         return {
+            "i_mp_ic": i_mp_ic,
             "i_mp": i_mp,
             "v_mp": v_mp,
             "p_mp": i_mp * v_mp,
+            "i_mp_string": i_mp,
+            "v_mp_string": np.sum(v_mp),
+            "p_mp_string": -sol.fun,
         }
 
+    if retry_ic:
+        # Try solution one more time using automated inital condition.
+        # Caller can detect this occurance by seeing change in i_mp_ic in
+        # return value.
+        return max_power_point_mismatched(
+            photocurrent,
+            saturation_current,
+            resistance_series,
+            resistance_shunt,
+            nNsVth,
+        )
+
     raise RuntimeError(f"unsuccessful solution: {sol}")
diff --git a/pvlib/tests/test_pvsystem.py b/pvlib/tests/test_pvsystem.py
index 4f007f3e4b..3de4dd6aee 100644
--- a/pvlib/tests/test_pvsystem.py
+++ b/pvlib/tests/test_pvsystem.py
@@ -2564,6 +2564,35 @@ def test_Array_temperature_missing_parameters(model, keys):
             "Ns": 60,
             "T": 25.0,
         },
+        {
+            "photocurrent": 6.2,
+            "saturation_current": 1.0e-8,
+            "n": 1.1,
+            "resistance_series": 0.0001,
+            "resistance_shunt": 5000.0,
+            "Ns": 60,
+            "T": 25.0,
+            "i_mp_ic": 5.8,
+        },
+        {
+            "photocurrent": np.array([5.8, 6.2]),
+            "saturation_current": 1.0e-8,
+            "n": 1.1,
+            "resistance_series": 0.0001,
+            "resistance_shunt": 5000.0,
+            "Ns": 60,
+            "T": 25.0,
+        },
+        {
+            "photocurrent": np.array([5.8, 6.2]),
+            "saturation_current": 1.0e-8,
+            "n": 1.1,
+            "resistance_series": 0.0001,
+            "resistance_shunt": 5000.0,
+            "Ns": 60,
+            "T": 25.0,
+            "i_mp_ic": None,
+        },
         {
             "photocurrent": np.array([5.8, 6.2]),
             "saturation_current": 1.0e-8,
@@ -2572,11 +2601,22 @@ def test_Array_temperature_missing_parameters(model, keys):
             "resistance_shunt": 5000.0,
             "Ns": 60,
             "T": 25.0,
-        }
+            "i_mp_ic": -1.0e14,
+        },
+        {
+            "photocurrent": np.array([5.8, 6.2]),
+            "saturation_current": 1.0e-8,
+            "n": 1.1,
+            "resistance_series": 0.0001,
+            "resistance_shunt": 5000.0,
+            "Ns": 60,
+            "T": 25.0,
+            "i_mp_ic": 5.6,
+        },
     ]
 )
 def test_max_power_point_mismatched(inputs):
-    """Test max power point computaiton for mismatched devices in series."""
+    """Test max power point computation for mismatched devices in series."""
 
     photocurrent = inputs["photocurrent"]
     saturation_current = inputs["saturation_current"]
@@ -2587,10 +2627,22 @@ def test_max_power_point_mismatched(inputs):
     T_K = scipy.constants.convert_temperature(inputs["T"], "Celsius", "Kelvin")
     nNsVth = inputs["n"] * inputs["Ns"] * k_B_J_per_K * T_K / q_C
 
-    pvsystem.max_power_point_mismatched(
-        photocurrent,
-        saturation_current,
-        resistance_series,
-        resistance_shunt,
-        nNsVth,
-    )
+    if "i_mp_ic" in inputs:
+        result = pvsystem.max_power_point_mismatched(
+            photocurrent,
+            saturation_current,
+            resistance_series,
+            resistance_shunt,
+            nNsVth,
+            i_mp_ic=inputs["i_mp_ic"],
+        )
+    else:
+        result = pvsystem.max_power_point_mismatched(
+            photocurrent,
+            saturation_current,
+            resistance_series,
+            resistance_shunt,
+            nNsVth,
+        )
+
+    print(result)

From 61753205671b95c323d58f6668f45ef5eef7d0c4 Mon Sep 17 00:00:00 2001
From: Mark Campanelli <mark.campanelli@gmail.com>
Date: Fri, 1 Dec 2023 11:34:18 -0700
Subject: [PATCH 05/14] Remove unused import

---
 pvlib/pvsystem.py | 1 -
 1 file changed, 1 deletion(-)

diff --git a/pvlib/pvsystem.py b/pvlib/pvsystem.py
index f7f3d889e0..18d01931d7 100644
--- a/pvlib/pvsystem.py
+++ b/pvlib/pvsystem.py
@@ -7,7 +7,6 @@
 import functools
 import io
 import itertools
-import numbers
 import os
 import inspect
 from urllib.request import urlopen

From cbe1768c1e5ebb25af253fa0d4e999d9a6ba82b2 Mon Sep 17 00:00:00 2001
From: Mark Campanelli <mark.campanelli@gmail.com>
Date: Fri, 1 Dec 2023 11:43:45 -0700
Subject: [PATCH 06/14] Add test for exceptional case

---
 pvlib/tests/test_pvsystem.py | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/pvlib/tests/test_pvsystem.py b/pvlib/tests/test_pvsystem.py
index 3de4dd6aee..087542863c 100644
--- a/pvlib/tests/test_pvsystem.py
+++ b/pvlib/tests/test_pvsystem.py
@@ -2646,3 +2646,27 @@ def test_max_power_point_mismatched(inputs):
         )
 
     print(result)
+
+def test_max_power_point_mismatched_error():
+    """
+    Test errored max power point computation for mismatched devices in series.
+    """
+    photocurrent = -6.2
+    saturation_current = 1.0e-8
+    resistance_series = 0.0001
+    resistance_shunt = 5000.0
+    q_C = scipy.constants.value("elementary charge")
+    k_B_J_per_K = scipy.constants.value("Boltzmann constant")
+    T_K = scipy.constants.convert_temperature(25.0, "Celsius", "Kelvin")
+    nNsVth = 1.1 * 60 * k_B_J_per_K * T_K / q_C
+
+    with pytest.raises(ValueError) as e_info:
+        pvsystem.max_power_point_mismatched(
+            photocurrent,
+            saturation_current,
+            resistance_series,
+            resistance_shunt,
+            nNsVth,
+        )
+
+    print(e_info)

From 999df203311f92c5aa15ddb8e23827016cdf21b7 Mon Sep 17 00:00:00 2001
From: Mark Campanelli <mark.campanelli@gmail.com>
Date: Fri, 1 Dec 2023 11:44:59 -0700
Subject: [PATCH 07/14] Linting

---
 pvlib/tests/test_pvsystem.py | 1 +
 1 file changed, 1 insertion(+)

diff --git a/pvlib/tests/test_pvsystem.py b/pvlib/tests/test_pvsystem.py
index 087542863c..f91d9726f9 100644
--- a/pvlib/tests/test_pvsystem.py
+++ b/pvlib/tests/test_pvsystem.py
@@ -2647,6 +2647,7 @@ def test_max_power_point_mismatched(inputs):
 
     print(result)
 
+
 def test_max_power_point_mismatched_error():
     """
     Test errored max power point computation for mismatched devices in series.

From 3ca7556b07bd8f9ed3df7fc144bf2708c0cf2cf3 Mon Sep 17 00:00:00 2001
From: Mark Campanelli <mark.campanelli@gmail.com>
Date: Fri, 1 Dec 2023 12:01:38 -0700
Subject: [PATCH 08/14] Catch exceptions in i_mp_ic computation and update
 docstring

---
 pvlib/pvsystem.py            | 21 +++++++++++++--------
 pvlib/tests/test_pvsystem.py |  6 +++---
 2 files changed, 16 insertions(+), 11 deletions(-)

diff --git a/pvlib/pvsystem.py b/pvlib/pvsystem.py
index 18d01931d7..827f62e44f 100644
--- a/pvlib/pvsystem.py
+++ b/pvlib/pvsystem.py
@@ -3048,17 +3048,22 @@ def max_power_point_mismatched(
     previous step may speed up computation. Algorithm falls back to automated
     computation of i_mp_ic if solution fails with provided i_mp_ic. The value
     of i_mp_ic used is returned along with i_mp (same value for all devices),
-    v_mp, and p_mp.
+    v_mp, p_mp, i_mp_string, v_mp_string, and p_mp_string.
     """
     if i_mp_ic is None:
-        i_mp_ic = max_power_point(
-            np.mean(photocurrent),
-            np.mean(saturation_current),
-            np.mean(resistance_series),
-            np.mean(resistance_shunt),
-            np.mean(nNsVth),
-        )["i_mp"]
         retry_ic = False
+        try:
+            i_mp_ic = max_power_point(
+                np.mean(photocurrent),
+                np.mean(saturation_current),
+                np.mean(resistance_series),
+                np.mean(resistance_shunt),
+                np.mean(nNsVth),
+            )["i_mp"]
+        except Exception as exc:
+            raise RuntimeError(
+                f"unsuccessful determination of i_mp_ic"
+            ) from exc
     else:
         retry_ic = True
 
diff --git a/pvlib/tests/test_pvsystem.py b/pvlib/tests/test_pvsystem.py
index f91d9726f9..0ab31b1d42 100644
--- a/pvlib/tests/test_pvsystem.py
+++ b/pvlib/tests/test_pvsystem.py
@@ -2648,11 +2648,11 @@ def test_max_power_point_mismatched(inputs):
     print(result)
 
 
-def test_max_power_point_mismatched_error():
+def test_max_power_point_mismatched_exception():
     """
     Test errored max power point computation for mismatched devices in series.
     """
-    photocurrent = -6.2
+    photocurrent = -6.2  # This is bad.
     saturation_current = 1.0e-8
     resistance_series = 0.0001
     resistance_shunt = 5000.0
@@ -2661,7 +2661,7 @@ def test_max_power_point_mismatched_error():
     T_K = scipy.constants.convert_temperature(25.0, "Celsius", "Kelvin")
     nNsVth = 1.1 * 60 * k_B_J_per_K * T_K / q_C
 
-    with pytest.raises(ValueError) as e_info:
+    with pytest.raises(RuntimeError) as e_info:
         pvsystem.max_power_point_mismatched(
             photocurrent,
             saturation_current,

From 1cca561f1a0af4bf32aa33c8dd16c9a67a1a2978 Mon Sep 17 00:00:00 2001
From: Mark Campanelli <mark.campanelli@gmail.com>
Date: Fri, 1 Dec 2023 12:09:30 -0700
Subject: [PATCH 09/14] Appease flake8 even more

---
 pvlib/pvsystem.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pvlib/pvsystem.py b/pvlib/pvsystem.py
index 827f62e44f..de68435abe 100644
--- a/pvlib/pvsystem.py
+++ b/pvlib/pvsystem.py
@@ -3062,7 +3062,7 @@ def max_power_point_mismatched(
             )["i_mp"]
         except Exception as exc:
             raise RuntimeError(
-                f"unsuccessful determination of i_mp_ic"
+                "unsuccessful determination of i_mp_ic"
             ) from exc
     else:
         retry_ic = True

From 58e44e07057b49fa8b9ebad919eb5b56b1f5d5ec Mon Sep 17 00:00:00 2001
From: Mark Campanelli <mark.campanelli@gmail.com>
Date: Fri, 1 Dec 2023 12:15:08 -0700
Subject: [PATCH 10/14] Test both exceptional cases

---
 pvlib/tests/test_pvsystem.py | 43 ++++++++++++++++++++++++++++++------
 1 file changed, 36 insertions(+), 7 deletions(-)

diff --git a/pvlib/tests/test_pvsystem.py b/pvlib/tests/test_pvsystem.py
index 0ab31b1d42..6ebff287ae 100644
--- a/pvlib/tests/test_pvsystem.py
+++ b/pvlib/tests/test_pvsystem.py
@@ -2648,18 +2648,47 @@ def test_max_power_point_mismatched(inputs):
     print(result)
 
 
-def test_max_power_point_mismatched_exception():
+@pytest.mark.parametrize(
+    'inputs',
+    [
+        {
+            "photocurrent": -6.2,  # This is bad.
+            "saturation_current": 1.0e-8,
+            "n": 1.1,
+            "resistance_series": 0.0001,
+            "resistance_shunt": 5000.0,
+            "Ns": 60,
+            "T": 25.0,
+        },
+        {
+            "photocurrent": -6.2,  # This is bad.
+            "saturation_current": 1.0e-8,
+            "n": 1.1,
+            "resistance_series": 0.0001,
+            "resistance_shunt": 5000.0,
+            "Ns": 60,
+            "T": 25.0,
+            "i_mp_ic": 5.6,
+        },
+    ]
+)
+def test_max_power_point_mismatched_exception(inputs, monkeypatch):
     """
     Test errored max power point computation for mismatched devices in series.
     """
-    photocurrent = -6.2  # This is bad.
-    saturation_current = 1.0e-8
-    resistance_series = 0.0001
-    resistance_shunt = 5000.0
+    # Monkey patch the objective function to force thrown exception.
+    monkeypatch.setattr(
+        "pvlib.pvsystem._negative_total_power", ZeroDivisionError
+    )
+
+    photocurrent = inputs["photocurrent"]
+    saturation_current = inputs["saturation_current"]
+    resistance_series = inputs["resistance_series"]
+    resistance_shunt = inputs["resistance_shunt"]
     q_C = scipy.constants.value("elementary charge")
     k_B_J_per_K = scipy.constants.value("Boltzmann constant")
-    T_K = scipy.constants.convert_temperature(25.0, "Celsius", "Kelvin")
-    nNsVth = 1.1 * 60 * k_B_J_per_K * T_K / q_C
+    T_K = scipy.constants.convert_temperature(inputs["T"], "Celsius", "Kelvin")
+    nNsVth = inputs["n"] * inputs["Ns"] * k_B_J_per_K * T_K / q_C
 
     with pytest.raises(RuntimeError) as e_info:
         pvsystem.max_power_point_mismatched(

From e40af1e5803b99927bc392bf790e3a77d68fe84c Mon Sep 17 00:00:00 2001
From: Mark Campanelli <mark.campanelli@gmail.com>
Date: Fri, 1 Dec 2023 14:47:50 -0700
Subject: [PATCH 11/14] Monkey patch solver to test exception

---
 pvlib/pvsystem.py            | 21 ++++++------
 pvlib/tests/test_pvsystem.py | 63 +++++++++++++-----------------------
 2 files changed, 32 insertions(+), 52 deletions(-)

diff --git a/pvlib/pvsystem.py b/pvlib/pvsystem.py
index de68435abe..59e8ece177 100644
--- a/pvlib/pvsystem.py
+++ b/pvlib/pvsystem.py
@@ -3052,18 +3052,14 @@ def max_power_point_mismatched(
     """
     if i_mp_ic is None:
         retry_ic = False
-        try:
-            i_mp_ic = max_power_point(
-                np.mean(photocurrent),
-                np.mean(saturation_current),
-                np.mean(resistance_series),
-                np.mean(resistance_shunt),
-                np.mean(nNsVth),
-            )["i_mp"]
-        except Exception as exc:
-            raise RuntimeError(
-                "unsuccessful determination of i_mp_ic"
-            ) from exc
+
+        i_mp_ic = max_power_point(
+            np.mean(photocurrent),
+            np.mean(saturation_current),
+            np.mean(resistance_series),
+            np.mean(resistance_shunt),
+            np.mean(nNsVth),
+        )["i_mp"]
     else:
         retry_ic = True
 
@@ -3074,6 +3070,7 @@ def max_power_point_mismatched(
         resistance_shunt,
         nNsVth,
     )
+
     sol = scipy.optimize.minimize(
         _negative_total_power, i_mp_ic, args=args, jac='3-point'
     )
diff --git a/pvlib/tests/test_pvsystem.py b/pvlib/tests/test_pvsystem.py
index 6ebff287ae..bf35e9a299 100644
--- a/pvlib/tests/test_pvsystem.py
+++ b/pvlib/tests/test_pvsystem.py
@@ -5,6 +5,7 @@
 from numpy import nan, array
 import pandas as pd
 import scipy.constants
+import scipy.optimize
 
 import pytest
 from .conftest import (
@@ -13,7 +14,6 @@
 import unittest.mock as mock
 
 from pvlib import inverter, pvsystem
-from pvlib import atmosphere
 from pvlib import iam as _iam
 from pvlib import irradiance
 from pvlib import spectrum
@@ -2648,48 +2648,31 @@ def test_max_power_point_mismatched(inputs):
     print(result)
 
 
-@pytest.mark.parametrize(
-    'inputs',
-    [
-        {
-            "photocurrent": -6.2,  # This is bad.
-            "saturation_current": 1.0e-8,
-            "n": 1.1,
-            "resistance_series": 0.0001,
-            "resistance_shunt": 5000.0,
-            "Ns": 60,
-            "T": 25.0,
-        },
-        {
-            "photocurrent": -6.2,  # This is bad.
-            "saturation_current": 1.0e-8,
-            "n": 1.1,
-            "resistance_series": 0.0001,
-            "resistance_shunt": 5000.0,
-            "Ns": 60,
-            "T": 25.0,
-            "i_mp_ic": 5.6,
-        },
-    ]
-)
-def test_max_power_point_mismatched_exception(inputs, monkeypatch):
-    """
-    Test errored max power point computation for mismatched devices in series.
-    """
-    # Monkey patch the objective function to force thrown exception.
+def test_max_power_point_mismatched_unsuccessful_solver(monkeypatch):
+    """Test errored max power point computation where solver is unsuccessful."""
+    photocurrent = 6.2
+    saturation_current = 1.0e-8
+    resistance_series =  0.0001
+    resistance_shunt = 5000.0
+    n = 1.1
+    Ns = 60
+    T = 25.0
+    T_K = scipy.constants.convert_temperature(T, "Celsius", "Kelvin")
+    k_B_J_per_K = scipy.constants.value("Boltzmann constant")
+    q_C = scipy.constants.value("elementary charge")
+    nNsVth = n * Ns * k_B_J_per_K * T_K / q_C
+
+    def minimize_monkeypatched(*_, **__):
+        """Return an unsuccessful solution from solver."""
+        return scipy.optimize.OptimizeResult(success=False)
+
+    # Monkey patch solver to return unsuccessfully.
     monkeypatch.setattr(
-        "pvlib.pvsystem._negative_total_power", ZeroDivisionError
+        scipy.optimize,
+        "minimize",
+        minimize_monkeypatched,
     )
 
-    photocurrent = inputs["photocurrent"]
-    saturation_current = inputs["saturation_current"]
-    resistance_series = inputs["resistance_series"]
-    resistance_shunt = inputs["resistance_shunt"]
-    q_C = scipy.constants.value("elementary charge")
-    k_B_J_per_K = scipy.constants.value("Boltzmann constant")
-    T_K = scipy.constants.convert_temperature(inputs["T"], "Celsius", "Kelvin")
-    nNsVth = inputs["n"] * inputs["Ns"] * k_B_J_per_K * T_K / q_C
-
     with pytest.raises(RuntimeError) as e_info:
         pvsystem.max_power_point_mismatched(
             photocurrent,

From 123fd99a9b296e432ad9886c9aafbe4334257c5f Mon Sep 17 00:00:00 2001
From: Mark Campanelli <mark.campanelli@gmail.com>
Date: Fri, 1 Dec 2023 14:49:37 -0700
Subject: [PATCH 12/14] Appease the flake8 monster

---
 pvlib/tests/test_pvsystem.py | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/pvlib/tests/test_pvsystem.py b/pvlib/tests/test_pvsystem.py
index bf35e9a299..6343d16b19 100644
--- a/pvlib/tests/test_pvsystem.py
+++ b/pvlib/tests/test_pvsystem.py
@@ -2649,10 +2649,12 @@ def test_max_power_point_mismatched(inputs):
 
 
 def test_max_power_point_mismatched_unsuccessful_solver(monkeypatch):
-    """Test errored max power point computation where solver is unsuccessful."""
+    """
+    Test errored max power point computation where solver is unsuccessful.
+    """
     photocurrent = 6.2
     saturation_current = 1.0e-8
-    resistance_series =  0.0001
+    resistance_series = 0.0001
     resistance_shunt = 5000.0
     n = 1.1
     Ns = 60

From fe7ab2a4763401573e828ed3df7d050ae812c334 Mon Sep 17 00:00:00 2001
From: Mark Campanelli <mark.campanelli@gmail.com>
Date: Sat, 2 Dec 2023 09:04:41 -0700
Subject: [PATCH 13/14] Add fixmes for remaining items to do

---
 pvlib/pvsystem.py            | 4 +++-
 pvlib/tests/test_pvsystem.py | 7 ++++---
 2 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/pvlib/pvsystem.py b/pvlib/pvsystem.py
index 59e8ece177..2594f01572 100644
--- a/pvlib/pvsystem.py
+++ b/pvlib/pvsystem.py
@@ -3028,7 +3028,7 @@ def combine_loss_factors(index, *losses, fill_method='ffill'):
 def _negative_total_power(current, *args):
     """
     Compute negative of total power generated by devices in series at
-    specified current.
+    specified current. Designed for use by scipy.optimize.minimize.
     """
     return -np.sum(current * v_from_i(current, *args))
 
@@ -3043,6 +3043,8 @@ def max_power_point_mismatched(
     i_mp_ic=None,
 ):
     """
+    FIXME Replace this with proper docstring.
+
     Compute maximum power info for (possibly) mismatched set of devices in
     series. When using this serially on time-series data, passing i_mp_ic from
     previous step may speed up computation. Algorithm falls back to automated
diff --git a/pvlib/tests/test_pvsystem.py b/pvlib/tests/test_pvsystem.py
index 6343d16b19..cdf7d8ff8c 100644
--- a/pvlib/tests/test_pvsystem.py
+++ b/pvlib/tests/test_pvsystem.py
@@ -2555,6 +2555,7 @@ def test_Array_temperature_missing_parameters(model, keys):
 @pytest.mark.parametrize(
     'inputs',
     [
+        # FIXME Need many more argument combinations in additional test cases.
         {
             "photocurrent": 6.2,
             "saturation_current": 1.0e-8,
@@ -2645,13 +2646,12 @@ def test_max_power_point_mismatched(inputs):
             nNsVth,
         )
 
+    # FIXME Replace this with test assertions.
     print(result)
 
 
 def test_max_power_point_mismatched_unsuccessful_solver(monkeypatch):
-    """
-    Test errored max power point computation where solver is unsuccessful.
-    """
+    """Test mismatched max power point computation where solver is unsuccessful."""
     photocurrent = 6.2
     saturation_current = 1.0e-8
     resistance_series = 0.0001
@@ -2684,4 +2684,5 @@ def minimize_monkeypatched(*_, **__):
             nNsVth,
         )
 
+    # FIXME Replace this with test assertions.
     print(e_info)

From 51439e9e568bdcbbf9784f41c341d85905c1a12e Mon Sep 17 00:00:00 2001
From: Mark Campanelli <mark.campanelli@gmail.com>
Date: Sat, 2 Dec 2023 09:08:01 -0700
Subject: [PATCH 14/14] Oh flake8 how I love you!

---
 pvlib/tests/test_pvsystem.py | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/pvlib/tests/test_pvsystem.py b/pvlib/tests/test_pvsystem.py
index cdf7d8ff8c..6c2143c5ed 100644
--- a/pvlib/tests/test_pvsystem.py
+++ b/pvlib/tests/test_pvsystem.py
@@ -2651,7 +2651,9 @@ def test_max_power_point_mismatched(inputs):
 
 
 def test_max_power_point_mismatched_unsuccessful_solver(monkeypatch):
-    """Test mismatched max power point computation where solver is unsuccessful."""
+    """
+    Test mismatched max power point computation where solver is unsuccessful.
+    """
     photocurrent = 6.2
     saturation_current = 1.0e-8
     resistance_series = 0.0001