Donut Lab has released independent test results confirming its solid-state battery can reach an 80% charge in just 4.5 minutes. Technology Research Centre VTT, an internationally recognized testing body, conducted the measurements. The results validate the Finnish company’s earlier claims about ultra-fast charging capability.
Highlights
- VTT testing confirmed the Donut Battery charges from 0–80% in 4.5 minutes at 11C rates without active cooling
- The battery retained 98.4–99.6% of charged capacity after rapid charging at extreme speeds
- No special compression or active cooling is required, simplifying battery pack design and reducing costs
- At 5C charging rates, the cell reached 100% in just over 12 minutes with full capacity available on discharge
Independent Testing Validates Fast-Charging Claims
VTT evaluated the Donut Battery’s charging speed and thermal behavior under worst-case conditions. The test simulated a scenario where the battery cell lacked active temperature controls. As a result, its temperature could rise freely at extremely high charging rates.
Researchers used two passive cooling setups for the measurements. The first surrounded the cell with two lightly compressed aluminum cooling plates. The second attached the cell to only one bottom cooling plate.
Charging Rates Far Exceed Lithium-Ion Standards
Charging rates are measured using C-rates, where 1C equals a full charge in one hour. Traditional lithium-ion batteries typically charge at 1C to 3C with active cooling. In contrast, the Donut Battery achieved significantly higher rates without it.
At 5C, the key results included:
- 80% state of charge reached in approximately 9.5 minutes
- 100% state of charge achieved in just over 12 minutes
- 100% of charged capacity available upon discharge
At the extreme 11C rate, performance remained strong:
- 0–80% charge completed in 4.5 minutes
- Full 100% charge reached in just over seven minutes
- 98.4–99.6% capacity retention confirmed after full charge and discharge
Simplified Pack Architecture Offers Cost Advantages
The testing conditions did not directly simulate cell behavior inside a battery pack. However, the results demonstrate clear advantages for pack-level integration. The Donut Battery does not require any particular compressive force. Additionally, it works well with passive cooling alone.
“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,” said Donut Lab CTO Ville Piippo. “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.”
The full measurement report is available on the I Donut Believe website.
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