Finnish technology company Donut Lab has taken a major step toward ultra-fast EV charging, publishing independent test results that confirm its solid-state battery can reach 80% charge in just 4.5 minutes.
The measurements were conducted by VTT Technical Research Centre of Finland, an internationally recognized testing body, validating the company’s earlier claims about extreme fast-charging capability.
Tested Under Worst-Case Conditions
VTT the Donut Battery’s charging speed and thermal behavior under deliberately harsh conditions. The scenario simulated a battery cell operating without active temperature control, allowing heat to rise freely at very high charging rates.
Two passive cooling configurations were used:
– The cell surrounded by two lightly compressed aluminum cooling plates
– The cell attached to a single bottom cooling plate
Unlike many next-generation solid-state designs, the Donut Battery does not require high compressive force or complex cooling systems — a key differentiator for real-world EV integration.
Charging Rates Far Beyond Lithium-Ion Norms
Charging performance is measured in C-rates, where:
– 1C = full charge in 1 hour
– 5C ≈ 12 minutes
– 11C ≈ 5–6 minutes
Traditional lithium-ion batteries typically charge at 1C to 3C, and that’s with active cooling systems in place.
By contrast, Donut Lab’s solid-state cell achieved dramatically higher rates — without active cooling.
At 5C:
– 80% state of charge in approximately 9.5 minutes
– 100% charge in just over 12 minutes
– 100% of charged capacity available upon discharge
At 11C:
– 0–80% charge completed in just 4.5 minutes
– Full charge reached in just over 7 minutes
– 98.4–99.6% capacity retention after full charge and discharge
These figures align with Donut Lab’s previously announced five-minute charging target and suggest performance well beyond conventional lithium-ion capabilities.
Simplified Pack Architecture = Lower Costs
While the test did not directly simulate full battery pack conditions, the findings highlight major integration advantages.
Many solid-state batteries require high compressive pressures, structural reinforcement, complex thermal management and volume expansion allowances of 15–20% during cycling.
According to Donut Lab CTO Ville Piippo, the Donut Battery avoids these complications.
“Unlike other solid-state batteries requiring high compressive pressures and undergoing volume changes of up to 15–20% during recharging cycles, the Donut Battery does not require special compression or more extensive cooling. This greatly simplifies the structure of battery packs and enables solutions that are cost-efficient, powerful, and better than traditional lithium-ion batteries in terms of energy and power density.”
What This Means for EV Drivers
If the technology scales successfully to automotive-grade battery packs, it could deliver:
– Charging times comparable to refueling
– Reduced cooling system complexity
– Higher energy and power density
– Lower pack-level production costs
Ultra-fast charging without heavy thermal management requirements would be particularly attractive in regions expanding high-power DC charging networks, including the U.S., UK and EU markets.
The full measurement report is available via Donut Lab’s I Donut Believe platform.
