Add PyBaMM 26.8 compatibility

.github/workflows/test.yml

@@ -31,17 +31,18 @@ jobs:
       matrix:
         include:
           # All Python versions against the latest PyBaMM
-          - {python-version: "3.10", pybamm-version: "26.7"}
-          - {python-version: "3.11", pybamm-version: "26.7"}
-          - {python-version: "3.12", pybamm-version: "26.7"}
-          - {python-version: "3.13", pybamm-version: "26.7"}
-          - {python-version: "3.14", pybamm-version: "26.7"}
+          - {python-version: "3.10", pybamm-version: "26.8"}
+          - {python-version: "3.11", pybamm-version: "26.8"}
+          - {python-version: "3.12", pybamm-version: "26.8"}
+          - {python-version: "3.13", pybamm-version: "26.8"}
+          - {python-version: "3.14", pybamm-version: "26.8"}
           # Older PyBaMM versions against the latest Python they support
           - {python-version: "3.13", pybamm-version: "25.12"}
           - {python-version: "3.14", pybamm-version: "26.3"}
           - {python-version: "3.14", pybamm-version: "26.4"}
           - {python-version: "3.14", pybamm-version: "26.5"}
           - {python-version: "3.14", pybamm-version: "26.6"}
+          - {python-version: "3.14", pybamm-version: "26.7"}
 
     steps:
       - uses: actions/checkout@v4

README.md

@@ -77,7 +77,7 @@ Thermal sub-model and heat-source options are injected automatically — pass th
 | `lead_acid.Full` | `Sulzer2019` | ❌ DAE | ❌ DAE | ✅ | ✅ |
 | `equivalent_circuit.Thevenin` | `ECM_Example` | ✅ | ✅ | ✅ ³ | ✅ ³ |
 
-¹ PyBaMM < 26.7 only — from 26.7 on `LOQS` is a DAE, use a `CellCoSim*` block instead.
+¹ Not on PyBaMM 26.7 — there `LOQS` is a DAE, use a `CellCoSim*` block instead. It is an ODE again from 26.8 on.
 
 ² PyBaMM < 26.7 only — pass `pybamm_solver=pybamm.CasadiSolver(mode="safe")`; the default `IDAKLUSolver` errors on `LOQS`. Fixed in 26.7.
 

pyproject.toml

@@ -32,7 +32,7 @@ dependencies = [
     # is skipped on Emscripten so the pure-Python parts of the toolbox
     # (`pathsim_batt.thermal`) still install in the browser.
     # Upper-bounded: each new minor release is vetted before being allowed.
-    "pybamm>=25.12,<26.8; sys_platform != 'emscripten'",
+    "pybamm>=25.12,<26.9;sys_platform != 'emscripten'",
 ]
 
 [project.optional-dependencies]

tests/cells/test_lead_acid.py

@@ -2,7 +2,8 @@
 
 Block / model matrix covered
 -----------------------------
-lead_acid.LOQS  — ODE on PyBaMM < 26.7, DAE from 26.7 on → CoSim blocks only there
+lead_acid.LOQS  — ODE (all 4 blocks), except on PyBaMM 26.7 where it is a DAE
+                  → CoSim blocks only there
 lead_acid.Full  — DAE → CoSim blocks only
 """
 
@@ -31,10 +32,10 @@
 
 # PyBaMM 26.7 registers "voltage as a state" centrally on every
 # BaseBatteryModel (default "true"), and lead-acid models don't support
-# disabling it, so LOQS is a DAE from 26.7 on and can no longer run in the
-# monolithic (ODE-only) blocks.
-_PYBAMM_VERSION = tuple(int(x) for x in pybamm.__version__.split(".")[:2])
-_LOQS_IS_ODE = _PYBAMM_VERSION < (26, 7)
+# disabling it, so LOQS is a DAE there and can't run in the monolithic
+# (ODE-only) blocks. 26.8 defaults it back to "false", making LOQS an ODE
+# again. Detect this from the model itself rather than the version number.
+_LOQS_IS_ODE = not pybamm.lead_acid.LOQS().algebraic
 
 # ---------------------------------------------------------------------------
 # lead_acid.LOQS  (ODE — all 4 blocks)
@@ -44,8 +45,8 @@
 class TestLeadAcidLOQS(unittest.TestCase):
     """lead_acid.LOQS with Sulzer2019 parameters.
 
-    ODE model (all 4 blocks) on PyBaMM < 26.7; DAE (CoSim blocks only) from
-    26.7 on. Sulzer2019 cutoffs: lower 1.75 V, upper 2.42 V, nominal capacity
+    ODE model (all 4 blocks), except on PyBaMM 26.7 where it is a DAE (CoSim
+    blocks only). Sulzer2019 cutoffs: lower 1.75 V, upper 2.42 V, nominal capacity
     17 A·h.
     """
 
@@ -57,32 +58,32 @@ def setUp(self):
     def _model(self):
         return pybamm.lead_acid.LOQS()
 
-    @unittest.skipUnless(_LOQS_IS_ODE, "LOQS is a DAE on PyBaMM >= 26.7")
+    @unittest.skipUnless(_LOQS_IS_ODE, "LOQS is a DAE on this PyBaMM version")
     def test_electrical_smoke(self):
         cell = run_electrical(self._model(), self.pv, current=17.0)
         assert_electrical_outputs(self, cell, self.v_lo, self.v_hi)
 
-    @unittest.skipUnless(_LOQS_IS_ODE, "LOQS is a DAE on PyBaMM >= 26.7")
+    @unittest.skipUnless(_LOQS_IS_ODE, "LOQS is a DAE on this PyBaMM version")
     def test_electrothermal_smoke(self):
         cell = run_electrothermal(self._model(), self.pv, current=17.0)
         assert_electrothermal_outputs(self, cell, self.v_lo, self.v_hi)
 
-    @unittest.skipIf(_LOQS_IS_ODE, "LOQS is a pure ODE on PyBaMM < 26.7")
+    @unittest.skipIf(_LOQS_IS_ODE, "LOQS is a pure ODE on this PyBaMM version")
     def test_monolithic_electrical_raises(self):
-        """LOQS is a DAE on PyBaMM >= 26.7 — CellElectrical must raise."""
+        """Where LOQS is a DAE (PyBaMM 26.7), CellElectrical must raise."""
         with self.assertRaises(NotImplementedError):
             CellElectrical(model=self._model(), parameter_values=self.pv)
 
-    @unittest.skipIf(_LOQS_IS_ODE, "LOQS is a pure ODE on PyBaMM < 26.7")
+    @unittest.skipIf(_LOQS_IS_ODE, "LOQS is a pure ODE on this PyBaMM version")
     def test_monolithic_electrothermal_raises(self):
-        """LOQS is a DAE on PyBaMM >= 26.7 — CellElectrothermal must raise."""
+        """Where LOQS is a DAE (PyBaMM 26.7), CellElectrothermal must raise."""
         with self.assertRaises(NotImplementedError):
             CellElectrothermal(model=self._model(), parameter_values=self.pv)
 
     def test_cosim_electrical_smoke(self):
         # On PyBaMM < 26.7, LOQS disables its Jacobian and IDAKLUSolver (the
         # co-sim default) errors without one; CasadiSolver works on every
-        # pinned version (25.12-26.7), so use it explicitly here.
+        # pinned version (25.12-26.8), so use it explicitly here.
         solver = pybamm.CasadiSolver(mode="safe")
         cell = CellCoSimElectrical(
             model=self._model(),
@@ -126,19 +127,19 @@ def test_cosim_electrothermal_smoke(self):
         sim.run(2)
         assert_electrothermal_outputs(self, cell, self.v_lo, self.v_hi)
 
-    @unittest.skipUnless(_LOQS_IS_ODE, "LOQS is a DAE on PyBaMM >= 26.7")
+    @unittest.skipUnless(_LOQS_IS_ODE, "LOQS is a DAE on this PyBaMM version")
     def test_electrical_soc_decreases(self):
         """SOC must decrease under discharge current."""
         cell = run_electrical(self._model(), self.pv, current=17.0, duration=60)
         self.assertLess(float(cell.outputs[2]), 1.0)
 
-    @unittest.skipUnless(_LOQS_IS_ODE, "LOQS is a DAE on PyBaMM >= 26.7")
+    @unittest.skipUnless(_LOQS_IS_ODE, "LOQS is a DAE on this PyBaMM version")
     def test_cutoff_values_match_parameter_set(self):
         cell = CellElectrical(model=self._model(), parameter_values=self.pv)
         self.assertAlmostEqual(cell._v_lower, self.v_lo)
         self.assertAlmostEqual(cell._v_upper, self.v_hi)
 
-    @unittest.skipUnless(_LOQS_IS_ODE, "LOQS is a DAE on PyBaMM >= 26.7")
+    @unittest.skipUnless(_LOQS_IS_ODE, "LOQS is a DAE on this PyBaMM version")
     def test_q_dot_nonzero_during_discharge(self):
         """Q_dot must be strictly positive during discharge (isothermal LOQS).
 
@@ -152,7 +153,7 @@ def test_q_dot_nonzero_during_discharge(self):
             "Q_dot is zero — thermal model may not compute heat sources",
         )
 
-    @unittest.skipUnless(_LOQS_IS_ODE, "LOQS is a DAE on PyBaMM >= 26.7")
+    @unittest.skipUnless(_LOQS_IS_ODE, "LOQS is a DAE on this PyBaMM version")
     def test_tamb_affects_temperature(self):
         """A warmer ambient temperature must yield a higher output cell temperature."""
         solver = pybamm.CasadiSolver(mode="safe")
@@ -183,7 +184,7 @@ def test_tamb_affects_temperature(self):
             ),
         )
 
-    @unittest.skipUnless(_LOQS_IS_ODE, "LOQS is a DAE on PyBaMM >= 26.7")
+    @unittest.skipUnless(_LOQS_IS_ODE, "LOQS is a DAE on this PyBaMM version")
     def test_soc_scale_factor(self):
         """SOC must be well below 1.0 after sustained discharge.