First vehicle tests of ProLogium and Rimac Technology's solid-state battery are not due until 2028 — two years after the partners showed a pack mockup at the Paris Motor Show. That is the hardest date in the program. Everything between now and then rests on hardware that does not yet exist.

The two companies presented the mockup at the Paris show. A mockup is a display object, not a validated product. The source material does not say whether the demonstrator contains live cells, instrumentation, or any thermal management hardware. That gap matters.

What is confirmed — and what is not

The stated timeline runs in three steps:

• Now: pack mockup on display at the Paris Motor Show.
• 2027: functional hardware and a complete battery pack expected.
• 2028: first vehicle tests planned.

Note the verbs. The 2027 and 2028 milestones are "expected" and "planned" — announced intentions, not confirmed capacity or production commitments. No supplier has signed volume agreements on this timeline in public view.

Neither company has disclosed a production site, an annual capacity figure, or a cell format for the program. The announcement also leaves open which Rimac vehicle platform will host the 2028 tests.

Who the partners are

ProLogium is a solid-state battery developer; Rimac Technology is the Croatian engineering and component arm of the Rimac group. The collaboration pairs a Tier-2 cell developer with a Tier-1 pack and vehicle-systems supplier. That structure fits automotive development norms — cell maker to pack integrator to OEM.

The partnership itself is not new. The Paris display confirms the collaboration is continuing. It does not confirm progress against any previously stated technical or industrial milestone, because none were cited.

Why 2028 is a soft target

Solid-state timing across the industry has slipped repeatedly, and this program shows the classic markers of early-stage work: a show mockup, no performance data, no named host vehicle, and no plant attached to the cells.

The single long caveat worth holding onto is this: a 2027 "complete battery pack" date implies cell samples, pack integration, and validation work all compress into roughly a year from a show mockup, which would be aggressive even for conventional chemistry, let alone solid-state.

No energy density figure, cycle life target, or fast-charge claim appears in the announcement. Trade readers should treat any downstream performance narrative as unverified until ProLogium publishes cell-level data.

What to watch next

Watch for functional hardware disclosures in 2027 — the first checkpoint that separates engineering from marketing. The 2028 vehicle tests are the second. A named OEM platform, a pilot line location, or a published cell specification would move this program from intention toward commitment. Absent those, the timeline remains a claim.