Overview
- VTT measured a Donut Lab cell at roughly 50% state of charge for 240 hours at 22–28°C and recovered 97.7% of the input, which the lab described as normal battery-type charge retention rather than supercapacitor behavior.
- Most of the observed drop came immediately after charging—about 60 mV in 10 seconds and 103 mV in the first hour—with only about 12 mV of drift from hour 10 to hour 240, suggesting low steady self-discharge but warranting longer tests.
- The retention result is the third in a weekly series following independent confirmations of ultra-fast charging at 11C (about 0–80% in 4.5 minutes) and high-temperature discharge performance up to 100°C.
- VTT’s public reports omit cell weight and physical dimensions and include no multi-thousand-cycle or pack-level testing, preventing independent verification of Donut Lab’s ≈400 Wh/kg and 100,000-cycle claims.
- Battery experts quoted in coverage, including MIT’s Donald R. Sadoway, say the reports are too generic to substantiate an extraordinary solid-state breakthrough as questions about dendrite control, manufacturability, and Donut Lab’s Verge Motorcycles timeline remain.