Donut Lab — Battery Specs Proven, But Not All Of Them - CleanTechnica

Donut Lab, a Finnish startup, recently announced its solid-state battery technology, drawing skepticism from experts who questioned whether the device was truly a battery or merely a supercapacitor. To address these doubts, Donut Lab commissioned testing by VTT, a reputable Finnish laboratory, and published detailed results on a dedicated website. The third VTT test, conducted in March 2026, demonstrated that the Donut Battery retains charge over extended periods, a behavior inconsistent with supercapacitors, which lose charge quickly when idle. This test involved charging the battery to about 50% and monitoring its voltage over ten days, confirming that the device behaves like a conventional battery. Donut Lab has released five test protocols so far, showcasing fast charging capabilities (80% charge in 4.5 minutes), performance under high temperatures, charge retention (97.7% after 10 days), pack-level operation in a Verge TS Pro motorcycle at 100 kW charging, and cycling resilience of a damaged cell.