Donut Lab has released results from its third independent evaluation of the Donut Battery, this time zeroing in on how well the solid-state cell retains a charge when idle. The findings, posted on the I Donut Believe website, push back against chatter that the technology might actually be a supercapacitor masquerading as a battery. Researchers put a sample cell through its paces under tightly controlled conditions to see just how long it could hold onto its juice.
Ville Piippo, CTO at Donut Lab, put it plainly: “Supercapacitors can discharge in a flash, but they also drain in a flash when left sitting. The Donut Battery, on the other hand, acts like a proper battery—it holds its charge for a seriously long time.” The test setup followed the same script as earlier rounds: a 1C capacity check to make sure the cell was up to spec, followed by charging it to around 50 percent state of charge. Then, it was left hooked up to a lab-grade battery tester at room temperature for ten straight days, with voltage readings taken every ten seconds.
The first ten hours showed the voltage settling down, and from there, the curve kept flattening out gradually over the remaining nine days. At the end of the stretch, a final discharge confirmed that the voltage drop lined up perfectly with the actual energy loss in watt-hours. That kind of behavior is textbook battery—nothing like the fast, linear voltage plunge you’d see from a supercapacitor under the same conditions.
This latest test backs up what Donut Lab has shown before and clears the way for more validation steps as the company pushes toward integrating the Donut Battery into electric vehicle production.
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