Donut Lab’s EV Battery Retains Nearly All Capacity After a −30°C Test
A 14-cell module retained 97% of its measured capacity after five hours at −30°C. Donut Lab’s battery chemistry is still undisclosed.
Donut Lab’s latest cold-weather test puts a specific number behind one of the Finnish startup’s boldest claims: its battery module retained 97% of its measured ampere-hour capacity after being held at −30°C for five hours. The result, from testing by Finland’s VTT Technical Research Centre, adds evidence that the cells can operate in deep cold without heaters or insulation. It doesn’t yet answer the bigger question for automakers: what chemistry is inside?
What the cold test measured
VTT tested a module made up of 14 Donut Lab cells in a temperature chamber. The module remained at −30°C (−22°F) for five hours, until it was frozen through. VTT then measured its capacity against an earlier result recorded at +25°C (about +77°F). The cold test found 97% of that earlier ampere-hour capacity remained.
Donut Lab has described its battery as retaining 99% capacity in these conditions. The reported module result is 97%, so the distinction between the company’s claim and the measured outcome matters. The company says the cells charged and discharged normally after the cold exposure, with no adverse effects from the test. The setup did not use heating, cooling or insulation systems.
That last point is the practical one. Electric vehicles can use thermal management to keep battery packs within a preferred temperature range, but those systems add equipment and draw energy. Donut Lab’s stated approach is to build temperature tolerance into the battery itself. If the performance holds in larger packs and in vehicle use, it could reduce the need to condition the battery in severe cold. The test alone doesn’t establish how much real-world range a vehicle would retain in winter.
Evidence is accumulating, but the chemistry remains unclear
The cold-weather result is part of a testing sequence that began after Donut Lab showed its solid-state battery at the Consumer Electronics Show in January. The company called it ready for use in original equipment manufacturer vehicle production and said it would share third-party results. At the unveiling, it also cited five-minute charging and an energy density of 400 watt-hours per kilogram.
Those figures would be significant if validated at a relevant scale and under conditions that reflect vehicle use. VTT has been assessing claims through individual tests, and Donut Lab has published supporting material on its I Donut Believe site. The new cold test adds one more data point; it isn’t a complete evaluation of a battery pack, vehicle integration, durability or charging performance.
Earlier, VTT tested the battery at 100°C. The report described a test in which the pouch’s thin membrane breached. Donut Lab’s observers have argued that the results are difficult to reconcile with a conventional lithium-ion cell using liquid electrolyte, which they say would be expected to release gas and catch fire in that situation. That interpretation has fed speculation about the battery’s chemistry, but the available test results don’t identify its ingredients.
A nickel-manganese-cobalt, or NMC, chemistry has been proposed as one possibility, though that explanation has also been challenged. Donut Lab has not resolved the mystery in the material described here. Until the company discloses the chemistry and publishes broader testing, comparison with established battery types remains limited.
Why cold performance matters to buyers
Low temperatures can reduce EV battery performance and available driving range, which makes a test at −30°C relevant to drivers in cold regions. But a cell-level result shouldn’t be mistaken for a winter range figure. Vehicle range also depends on pack design, cabin heating, route, speed and how the battery is managed. The VTT result speaks to the module’s measured capacity after exposure, not the distance a particular car could travel.
Cold affects combustion vehicles, too, including their fuel efficiency. That doesn’t make the two powertrains identical in winter: drivers still need to account for their vehicle’s own energy use and operating limits. For EV makers, battery tolerance could complement thermal management and help reduce the amount of energy spent warming a pack. Whether it changes ownership costs or charging routines would depend on how the technology performs in production vehicles.
A different battery race is taking shape
Donut Lab’s work is unfolding as established automakers pursue other chemistries. Ford and General Motors have discussed lithium manganese-rich batteries, often shortened to LMR, as a way to target lower costs than NMC while offering greater energy density than lithium iron phosphate, or LFP. The source reports that GM plans to produce LMR batteries at its existing EV battery factory in Spring Hill, Tennessee.
Ford, meanwhile, has previously described investment in US-based LFP production as part of its effort to make EVs more affordable. The source links that strategy to the expected volume production of the Fathom electric pickup truck next year and says the truck is expected to cost just under $30,000. It suggests LFP may be used, though that remains a forecast in the source rather than a confirmed specification.
These battery paths answer different priorities: energy density, cost and performance in difficult temperatures. Donut Lab’s cold test adds an unusual claim to that mix, but repeatable results across more cells, packs and operating conditions will determine how much it matters to vehicle makers and buyers. The company’s test information, VTT report and test video provide the next level of detail.
