Donut Lab Puts Its EV Battery Through a –22 Degree F Cold Test

Donut Lab Subjected Its EV Battery to a Cold TestDonut LabDonut Lab says its battery technology has cleared another round of testing, this time showing that a complete battery module retained 97 percent of its capacity after being frozen to –22 degrees F (–30 degrees C).

The Finnish technology company, which has been developing an unconventional solid-state battery architecture, commissioned Finnish research organization VTT to conduct the test on a 14-cell battery module. Unlike a test performed on an individual cell, the experiment was designed to evaluate the performance of an assembled module under extreme cold.

The results are potentially significant for electric vehicles, as cold-weather operation can sharply reduce available battery energy and charging performance.

For the test, VTT placed the 48-volt module in a temperature chamber at –22 degrees F for five hours, without insulation or heat. Sensors confirmed that the cells themselves reached and remained at the target temperature.

A baseline, established at 77°F, the module delivered 27.77 amp-hours, equivalent to 1,354 watt-hours of energy, when fully discharged. After the module was, the same discharge test produced 26.8 amp-hours—97 percent of the original capacity. Measured energy output, however, fell to 1,254 watt-hours, or about 93 percent of the baseline, because battery voltage naturally drops at extremely low temperatures.

In other words, the cells retained nearly all of their capacity in terms of amp-hours, but the extreme cold reduced the amount of energy they could actually deliver because of the lower voltage. Donut Lab says that effect should be less pronounced in a vehicle, where the battery would be enclosed in an insulated housing and would generate heat during operation.

Donut Lab's solid-state batteries are used in Verge electric motorcycles.Verge Motorcycles

That distinction is important because Donut Lab's headline claim at CES 2026 was that its battery could retain 99 percent of its capacity at –22 degrees F. The latest test did not quite reach that figure, but the company says the results support the claim because the tested module deliberately lacked insulation and heating.

"Winter is the moment of truth for every battery," Donut Lab CEO Marko Lehtimäki said.

The cold test is the latest in a series of evaluations performed by VTT on Donut Lab's first-generation cells. The testing program also covered five-minute fast charging, exposure to temperatures as high as 212 degrees F (100 degrees C), self-discharge, repeated fast charging of a damaged cell, swelling and pressure, and energy density.

At CES earlier this year, Donut Lab also said its battery could charge from 10 to 80 percent in five minutes, although such claims remain considerably different from the performance of batteries currently used in mainstream EVs.

The company says the VTT testing of its Gen1 cells is now complete and that development is moving toward its next-generation technology. Among the areas Donut Lab is pursuing is a bipolar cell structure, which it says could enable further improvements at the system level.