> ## Documentation Index > Fetch the complete documentation index at: https://docs.ionworks.com/llms.txt > Use this file to discover all available pages before exploring further. # Fit From Measurements > Submit an ECM fit using measurements stored in the platform. Returns ``202 Accepted`` with ``{"job_id": ..., "status": ...}``. Poll ``GET /jobs/{job_id}`` for the result. Always includes RC-pair parameters in the result (authenticated endpoint). ## OpenAPI ````yaml https://api.ionworks.com/openapi.json post /ecm/fit-from-measurements openapi: 3.1.0 info: title: FastAPI version: 0.1.0 servers: - url: https://api.ionworks.com description: Production security: [] paths: /ecm/fit-from-measurements: post: tags: - ecm-project summary: Fit From Measurements description: |- Submit an ECM fit using measurements stored in the platform. Returns ``202 Accepted`` with ``{"job_id": ..., "status": ...}``. Poll ``GET /jobs/{job_id}`` for the result. Always includes RC-pair parameters in the result (authenticated endpoint). operationId: fit_from_measurements_ecm_fit_from_measurements_post requestBody: content: application/json: schema: $ref: '#/components/schemas/FitFromMeasurementsRequest' required: true responses: '202': description: Successful Response content: application/json: schema: {} '422': description: Validation Error content: application/json: schema: $ref: '#/components/schemas/HTTPValidationError' components: schemas: FitFromMeasurementsRequest: properties: measurements: items: $ref: '#/components/schemas/FitMeasurementRequest' type: array minItems: 1 title: Measurements description: One or more measurements to fit jointly. ecm_options: $ref: '#/components/schemas/FitECMOptions' type: object required: - measurements title: FitFromMeasurementsRequest description: Request body for fitting ECM from database measurements. HTTPValidationError: properties: detail: items: $ref: '#/components/schemas/ValidationError' type: array title: Detail type: object title: HTTPValidationError FitMeasurementRequest: properties: id: type: string title: Id description: Measurement ID. start_step: anyOf: - type: integer - type: 'null' title: Start Step description: Optional inclusive start step for filtering. end_step: anyOf: - type: integer - type: 'null' title: End Step description: Optional inclusive end step for filtering. initial_soc: anyOf: - type: number maximum: 1 minimum: 0 - type: 'null' title: Initial Soc description: >- Known initial SOC (0–1) at the start of this measurement. When None and an ``ocv_soc_curve`` is provided in ``ecm_options``, soc0 is auto-seeded by inverting V[s] = OCV(soc0) − I[s]·R0(soc0) after a warm-up fit. Falls back to coulomb-count for single-measurement runs without an OCV curve. capacity: anyOf: - type: number exclusiveMinimum: 0 - type: 'null' title: Capacity description: >- Known cell capacity in Ah for this measurement. When provided for every measurement, the per-measurement values are used; otherwise the shared ``ecm_options.capacity`` (or an estimate) applies. Per-measurement capacity is all-or-none across measurements. type: object required: - id title: FitMeasurementRequest description: One measurement to include in an ECM fit. FitECMOptions: properties: num_rcs: type: integer maximum: 5 minimum: 0 title: Num Rcs description: Number of RC pairs. default: 2 fit_ocv: type: boolean title: Fit Ocv description: Whether to fit OCV or use provided. default: true capacity: anyOf: - type: number exclusiveMinimum: 0 - type: 'null' title: Capacity description: Known cell capacity in Ah. Estimated if not provided. regularization: type: number minimum: 0 title: Regularization description: >- Smoothness-prior strength on the R0 / RC parameter curves (never OCV). Maps to scale = 5 / regularization; 0 disables the prior. Defaults to 0 (off). default: 0 ocv_soc_curve: anyOf: - $ref: '#/components/schemas/OcvSocCurve' - type: 'null' description: >- Open-circuit voltage curve as (soc, ocv) arrays. When provided, OCV-fitting is skipped and OCV is interpolated from the curve. Mutually exclusive with measurement Open-circuit voltage [V] columns. bounds_capacity: anyOf: - $ref: '#/components/schemas/CapacityBounds' - type: 'null' description: >- Search bounds (Ah) for capacity fitting. Providing this (with ocv_soc_curve and no capacity) opts in to fitting capacity; without it capacity is coulomb-count estimated. num_knots: anyOf: - type: integer maximum: 64 minimum: 1 - type: 'null' title: Num Knots description: >- Number of SOC knots for RC alpha + default beta resolution. Service default applies when None. num_knots_r0: anyOf: - type: integer maximum: 64 minimum: 1 - type: 'null' title: Num Knots R0 description: Number of SOC knots for R0(SoC). Service default applies when None. knot_schedule: anyOf: - items: type: integer type: array - type: 'null' title: Knot Schedule description: >- Multi-resolution beta knot schedule (strictly increasing positive ints ending at num_knots). Auto-derived when None. clamp_boundary_knots: type: boolean title: Clamp Boundary Knots description: >- When True (default), clamp boundary R0/alpha/beta knot values to within ``clamp_max_ratio`` of their interior neighbour. Set False if you build R_rc(soc)=alpha(soc)/beta(soc) symbolically downstream — the ratio is well behaved even at unobserved boundary knots and clamping costs fit quality. default: true clamp_max_ratio: type: number exclusiveMinimum: 1 title: Clamp Max Ratio description: >- Cap boundary knot values at ``clamp_max_ratio`` × their interior neighbour (only when ``clamp_boundary_knots`` is True). Larger values preserve more SoC variation; smaller values are stricter against R_rc=alpha/beta blow-ups that destabilise pybamm forward simulations. Default 10. default: 10 type: object title: FitECMOptions description: ECM fitting hyperparameters shared across all measurements. ValidationError: properties: loc: items: anyOf: - type: string - type: integer type: array title: Location msg: type: string title: Message type: type: string title: Error Type input: title: Input ctx: type: object title: Context type: object required: - loc - msg - type title: ValidationError OcvSocCurve: properties: soc: items: type: number type: array minItems: 2 title: Soc description: Strictly increasing SOC knot values in [0, 1]. ocv: items: type: number type: array minItems: 2 title: Ocv description: OCV values in volts at each SOC knot. type: object required: - soc - ocv title: OcvSocCurve description: Open-circuit voltage as a function of state of charge. CapacityBounds: properties: lo: type: number exclusiveMinimum: 0 title: Lo description: Lower bound (Ah). hi: type: number exclusiveMinimum: 0 title: Hi description: Upper bound (Ah). type: object required: - lo - hi title: CapacityBounds description: Search bounds for capacity fitting (Ah). ````