battwin

The Battery Twin Envelope (BTE): an open specification — plus reference SDK — for expressing and exchanging battery digital twins.

A battery digital twin is, as a data artifact, a composition: an identity, a specification, one or more models, an estimated state, and links to measurement data. Today every platform encapsulates that composition privately. battwin defines it openly, as a small immutable JSON document — the twin envelope — that references existing open standards instead of reinventing them:

BattINFO records ─────┐  (identity & specification, by IRI)
BPX / BattMo params ──┼──▶  Battery Twin Envelope (.twin.json)  ──▶ registries,
BDF datasets & feeds ─┘  (models & data, by reference)               platforms,
                                                                     archives

Envelopes are documents, not engines: how a twin is hosted, simulated, or synchronized is an implementation concern; how it is expressed is a community concern. The full format is defined in SPEC.md.

Documentation: digibatt.github.io/battwin

Installation

pip install battwin

Dependencies: pydantic and jsonschema — nothing else. The optional battwin[shacl] extra (pyshacl) adds a third, SHACL-based validation layer over the JSON-LD rendering.

Quickstart

from battwin import new_envelope, save, validate_file

twin = new_envelope(label="Bench cell 001", chemistry="LFP")
save(twin, "bench-cell-001.twin.json")
assert validate_file("bench-cell-001.twin.json") == []

Updating a twin creates a new, hash-chained version — envelopes are immutable:

from datetime import datetime, timezone
from battwin import StateSnapshot, load, save

v1 = load("bench-cell-001.twin.json")
v2 = v1.next_version(
    state=StateSnapshot(
        as_of=datetime.now(timezone.utc),
        state_of_charge=0.8,
        method="coulomb_counting",
        source_data="data/SINTEF__001__20260707_001.bdf.csv",
    )
)
assert v2.version.previous == v1.content_hash()  # verifiable lineage
save(v2, "bench-cell-001.v2.twin.json")

And from the command line:

battwin init --label "Bench cell 001" --chemistry LFP -o cell.twin.json
battwin validate cell.twin.json
battwin validate --shacl cell.twin.json         # + SHACL shapes layer (battwin[shacl])
battwin show cell.twin.json
battwin diff cell.twin.json cell.v2.twin.json   # checks the version chain
battwin schema                                  # print the packaged JSON Schema
battwin context                                 # print the packaged JSON-LD context

battwin schema and battwin context print the language-neutral contracts to stdout, so non-Python consumers can pull them without touching the SDK.

What's in an envelope

{
  "bte_version": "0.1.1",
  "id": "urn:bte:energizer-cr2032:demo-001",
  "identity":      { "label": "...", "serial_number": "...", "battinfo_iri": "...", "passport_id": "..." },
  "specification": { "battinfo_record": "https://w3id.org/battinfo/cell-spec/...", "chemistry": "Li/MnO2" },
  "models":        [ { "kind": "bpx", "name": "...", "source": "params.bpx.json", "validity": { "...": "..." } } ],
  "state":         { "as_of": "2026-07-07T12:00:00Z", "state_of_charge": 0.82, "energy_throughput_kwh": 0.00013, "equivalent_full_cycles": 0.0006, "method": "coulomb_counting" },
  "data":          [ { "kind": "bdf", "uri": "data/SINTEF__DEMO-001__20260707_001.bdf.csv", "role": "cycling" } ],
  "provenance":    { "created": "...", "created_by": "...", "tool": "battwin/0.4.0" },
  "extensions":    { "lab:fixture_id": "bench-07" },
  "version":       { "number": 2, "previous": "sha256:...", "changed": ["state"], "timestamp": "..." }
}

Vendor- or tool-specific facts that aren't (yet) canonical go in extensions under namespaced keys — see SPEC.md §3.8.

A complete example lives at examples/cr2032.twin.json, and examples/p45b/ carries an openly licensed ECM parameter set for the Molicel INR21700-P45B used by the hands-on tutorials. Envelopes also render as JSON-LD (save(..., jsonld=True)) using the packaged context, so they slot into linked-data pipelines alongside BattINFO — and with the battwin[shacl] extra installed, battwin validate --shacl checks that rendering against the packaged SHACL shapes as a third validation layer.

Non-goals

battwin deliberately does not:

• run simulations (that's PyBaMM, BattMo, and the platforms built on them);
• host twins or define sync/REST protocols;
• manage fleets or tenants;
• acquire measurement data (see battfeed for source→BDF collection, and the BDF toolchain for files at rest);
• replace BattINFO, BPX, or BDF — it composes them by reference.

Related projects

Python support

Python 3.10 – 3.12.

Acknowledgements

This project has received support from European Union research and innovation programs under grant agreement 101103997 – DigiBatt.

License

Apache-2.0. See LICENSE and NOTICE.