> ## Documentation Index
> Fetch the complete documentation index at: https://mintlify.com/pybamm-team/PyBaMM/llms.txt
> Use this file to discover all available pages before exploring further.

# ScipySolver

> The ScipySolver wraps scipy.integrate.solve_ivp to solve ODE-only battery models. It is the simplest solver and requires no additional compiled dependencies.

`pybamm.ScipySolver` wraps [`scipy.integrate.solve_ivp`](https://docs.scipy.org/doc/scipy/reference/generated/scipy.integrate.solve_ivp.html) and is the easiest way to get started when your model produces a pure ODE system.

<Warning>
  `ScipySolver` does **not** support DAE (differential-algebraic) models. Most lithium-ion models (SPM, SPMe, DFN) include algebraic equations and require `CasadiSolver` or `IDAKLUSolver`.
</Warning>

## Constructor

```python theme={null}
pybamm.ScipySolver(
    method="BDF",
    rtol=1e-6,
    atol=1e-6,
    extrap_tol=None,
    on_extrapolation=None,
    extra_options=None,
)
```

<ParamField path="method" type="str" default="&#x22;BDF&#x22;">
  Integration method passed to `solve_ivp`. Supported values:

  | Method     | Description                                     |
  | ---------- | ----------------------------------------------- |
  | `"BDF"`    | Implicit BDF (default); good for stiff problems |
  | `"RK45"`   | Explicit Runge-Kutta 4(5); non-stiff problems   |
  | `"RK23"`   | Explicit Runge-Kutta 2(3)                       |
  | `"DOP853"` | Explicit Runge-Kutta of order 8                 |
  | `"Radau"`  | Implicit Runge-Kutta (Radau IIA); stiff         |
  | `"LSODA"`  | Automatic stiff/non-stiff switching             |
</ParamField>

<ParamField path="rtol" type="float" default="1e-6">
  Relative tolerance.
</ParamField>

<ParamField path="atol" type="float" default="1e-6">
  Absolute tolerance.
</ParamField>

<ParamField path="extrap_tol" type="float | None" default="0">
  Tolerance for detecting extrapolation beyond the solved interval.
</ParamField>

<ParamField path="on_extrapolation" type="str" default="&#x22;warn&#x22;">
  Behaviour on extrapolation: `"warn"`, `"error"`, or `"ignore"`.
</ParamField>

<ParamField path="extra_options" type="dict | None" default="{}">
  Additional keyword arguments forwarded to `solve_ivp` (e.g. `{"max_step": 10}`).
</ParamField>

***

## Examples

<CodeGroup>
  ```python Basic ODE solve theme={null}
  import pybamm

  # SPM with "reformulated" option produces a pure ODE
  model = pybamm.lithium_ion.SPM()

  param = pybamm.ParameterValues("Chen2020")
  solver = pybamm.ScipySolver(method="BDF")

  sim = pybamm.Simulation(model, parameter_values=param, solver=solver)
  sol = sim.solve([0, 3600])
  print(sol["Terminal voltage [V]"].entries[-1])
  ```

  ```python Non-stiff with RK45 theme={null}
  import pybamm

  solver = pybamm.ScipySolver(method="RK45", rtol=1e-8, atol=1e-8)
  ```

  ```python Pass extra solve_ivp options theme={null}
  import pybamm

  solver = pybamm.ScipySolver(
      method="BDF",
      extra_options={"max_step": 1.0, "dense_output": True},
  )
  ```
</CodeGroup>

<Note>
  Sensitivity analysis is not supported by `ScipySolver`. Use `IDAKLUSolver` if you need parameter sensitivities.
</Note>