ProLogium-Rimac Solid-State Pack Sets 2028 Road-Test Target

A mockup in Paris and a dated plan

ProLogium and Rimac Technology have finished a concept mockup of a battery pack built around solid-state pouch cells. They are showing it at the 2026 Paris Motor Show, about a year after the two companies signed a memorandum of understanding to build a next-generation battery platform.13 The design is a pouch cell-to-pack layout: ProLogium supplies the cells and Rimac Technology handles the pack engineering.12 The partners say they will move from the mockup to a working battery segment, then to a full-size working pack, and finally to tests inside a vehicle.12

The dates are specific. Rimac Technology plans to show the working segment at CES 2027 and has set the second half of 2027 as the milestone for a full working pack.13 Tests in a vehicle and on public roads are planned for the second half of 2028.11 Automotive World read the schedule as a sign that integration, not cell chemistry, now sets the pace for solid-state batteries. It also noted that with road testing more than two years off, any production car using the pack is further away still.14

That reading is right. The Paris display is a staging post, not a product launch. It is still worth paying attention to, because it addresses the part of solid-state development that gets the least publicity and usually takes the longest: fitting promising cells into a pack that a carmaker can actually put in a car.

Why the pack matters as much as the cell

Both companies say good cells are not enough. ProLogium founder and CEO Vincent Yang said automotive use also needs engineering to fit cells into a pack with the right architecture and thermal management. He called the Paris showing the baseline of the collaboration.11 Daniel Kišić, Rimac Technology's principal product architect, said his team is testing many integration approaches side by side on working segments. These cover thermal management, swelling, cell integration and overall system design. Some favour energy density and lower weight, while others favour performance.11

Swelling is the telling detail. Automotive World singled it out as a practical hurdle for the solid-state pouch cells Rimac is designing around.14 Solid-state pouch cells can change dimension as they charge and discharge, and a pack has to allow for that without losing structural or thermal integrity. Rimac's willingness to name the problem openly suggests the engineering is real work, not just presentation.

Kišić also described what carmakers would get. If the pack is validated at vehicle level, he expects large weight savings. Automakers could then choose more stored energy at the same weight, a smaller and lighter pack for the same range, or something in between.11 That flexibility is commercially sensible. Mass-market buyers mostly care about cost per kilometre of range, while performance brands care about weight and power.

Measuring today's plan against last year's

The new timeline makes more sense next to what the partners said when they signed the MOU at IAA Munich in September 2025. Rimac Technology COO Nurdin Pitarević said then that the goal was a first sample by the end of 2027 and a B-sample ready for in-vehicle testing by 2028, followed by small-scale production by 2030.15 He described a target pack of about 100 kWh with 500–600 km of range and 10–80 percent charging in under ten minutes. He also said Rimac was about halfway to its goals on safety, range and charging, and that ProLogium was about halfway on the cell.15

The Munich demonstrator promised even more. Coverage at the time said the 100 kWh pack charged from 10 to 80 percent in six and a half minutes. It used 285 litres against 320 for a comparable cylindrical-cell pack and weighed 384 kg against 470 kg.18 The same report said production versions were expected in late 2027.18

The 2026 roadmap still roughly matches Pitarević's dates: a working pack in late 2027 and vehicle testing in 2028.1315 The more optimistic hints about production arriving in 2027 no longer appear. The schedule has not slipped badly, but the language is clearly more cautious. Given how many solid-state timelines across the industry have broken, that caution is a strength. One thing the 2026 announcements leave out is notable: they do not repeat the charging-time and range figures that headlined the IAA debut.

ProLogium's broader push to scale

The collaboration sits inside a busy year for ProLogium. In September the company said its Gen 3.5 lithium ceramic battery had entered mass production in Taiwan. A TÜV report put its 185.4 Ah large-format cell at 381 Wh/kg and 903 Wh/L.1 UL Solutions tested the cell under China's GB/T 43568-2026 method. After six hours under vacuum at 120°C it lost less than 0.05 percent of its weight, well under the 0.5 percent limit for all-solid-state classification.1 That matters because the term "solid-state" is now used for many different designs, and the test gives ProLogium an independent basis for using it.5

Next comes Gen 4, which uses a fully inorganic "superfluidized" electrolyte. ProLogium estimates that only about 10 percent of its existing gigascale line will need changes to make it.10 On September 24, Mercedes-Benz got priority access to Gen 4 cells under a joint test agreement. ProLogium says these cells reach up to 400 Wh/kg and charge from 5 to 80 percent in 6.4 minutes.8 On the money side, ProLogium agreed in May to go public through a SPAC merger with Translational Development Acquisition Corp. The deal values the company at about $3.8 billion and is expected to close in the second half of 2026.3

Where the numbers don't agree

The biggest gaps in the reporting are about factory capacity, and they deserve attention. ProLogium describes its Taoyuan site as a Giga-level factory. CarNewsChina reported an initial operating capacity of just 0.5 GWh, with plans to grow to 1–2 GWh. By its estimate, 0.5 GWh a year is enough for roughly 6,250 packs of 80 kWh.5 Electrive put Taoyuan's capacity at 3 GWh.10

The Dunkirk figures differ too. ProLogium's own materials say the first phase will reach 4.0 GWh of designed annual capacity, gradually, by 2030, with a site maximum of 44 GWh.11 Electrive reported a first-phase starting capacity of 0.8 GWh due in 2028.10 Battery-News cited up to 48 GWh for the full site.9 Electrek reported production ramping between Q4 2028 and Q1 2029, with deliveries from Q2 2029.3 Automotive News Europe, via Yahoo Autos, said last year that French media had reported a one-year delay to Dunkirk's start date.15

The most reasonable way to reconcile these is to treat the higher numbers as nameplate goals and the lower ones as what will actually be running in the first few years. Either way, the takeaway is the same: ProLogium can make cells today, but not yet at automotive scale. That fits the Rimac schedule. A pack ready for road tests in late 2028 would arrive around the time Dunkirk's first phase starts up.

The clean-energy angle beyond cars

This matters beyond supercars because of energy density and safety. ProLogium says its inorganic electrolyte does not burn and that its ceramic separator keeps the electrodes apart even under heat and mechanical stress.2 UL Solutions' ARC testing, using the Heat-Wait-Seek method, found no thermal runaway in its superfluidized cells.3 Lighter, safer packs mean less material per kilometre driven. They could also reduce the fire-safety work that drives up costs for large battery installations.

ProLogium is already pitching beyond vehicles. Yang said money from the listing would help expand into data centers, aerospace and robotics while EV work continues.3 One analysis noted the company is pointing its newest cells at AI data centers. It added that ProLogium has not named a data-center customer, contract or delivery date, nor given pricing or a qualification timeline.4 So the stationary-storage story is still a stated ambition, not a product line. For grid-scale storage in particular, where cost per kilowatt-hour matters far more than weight, cheaper chemistries are likely to keep the advantage for now. ProLogium's better case is in safety-critical, space-limited installations.

The verdict

The Paris mockup is the least eye-catching milestone in this partnership, but it may say the most. ProLogium has cells in production and backing from Mercedes, and Rimac Technology has pack engineering and existing work with major carmakers. That is about as strong a team as any Western solid-state effort has.819 The open questions are the same ones that have held back solid-state batteries for a decade: cost, yield, factory scale, and whether cell-level numbers hold up in a finished pack.5 The CES 2027 segment and the late-2027 working pack are the next dated tests of whether the claims hold up.