By ATN
Summary: Donut Lab commissioned independent testing by VTT Technical Research Centre of Finland to evaluate the charging performance and thermal behaviour of its serially producible solid-state “Donut Battery.” Under worst-case conditions without active temperature control, the cell demonstrated ultra-fast charging capability, achieving 80% state of charge in 4.5 minutes and full charge in just over seven minutes at 11C, while maintaining up to ~99% usable capacity. The design’s tolerance for passive cooling and lack of compression requirements indicates potential simplification of battery pack architecture.
Key engineering takeaway: Independent tests confirmed that the solid-state cell can sustain extremely high C-rates (5C–11C) without active thermal management, while retaining nearly full discharge capacity. The cell’s minimal swelling and absence of compressive force requirements enable simpler mechanical integration and passive cooling strategies at pack level.
Why it matters: Ultra-fast charging with reduced thermal and mechanical constraints could lower battery system complexity, weight, and cost while improving vehicle uptime. If scalable to pack level, the technology addresses two major barriers to EV adoption—charging time and pack architecture complexity—supporting broader deployment of high-performance electrified vehicles.
Donut battery charges from 0-80% in less than 5 minutes
Donut Lab commissioned the internationally recognised Technology Research Centre VTT to measure the features of the first serially producible solid state battery under independent research conditions. The first test, focusing on charging speed, shows that the Donut Battery can be charged in only five minutes as previously announced.
Technology company Donut Lab has published the results of the first measurements analysing the features of its solid state battery. The tests, conducted by Technology Research Centre VTT, evaluate the Donut Battery’s charging speed and thermal behaviour during charging. It simulates a worst-case scenario, in which the battery cell lacks active temperature controls and its temperature can rise freely at extremely high charging rates.
The measurement was done using two passive cooling configurations: in the first, the cell was surrounded by two lightly compressed aluminium cooling plates, and in the other the cell was attached to only one bottom cooling plate. Recharging rates are indicated using C-rates, where 1C means that the battery is charged from empty to full in one hour (e.g. 5C = ~12 min, 11C = ~5-6 min). Traditional lithium-ion batteries typically charge at 1C to 3C with active cooling, whereas in this measurement the charging power rises to significantly higher rates without active cooling. The test started with a standard discharge capacity test at 1C, which was followed by rapid charging tests (at 5C and 11C) with both cooling configurations.
The results are in line with the five-minute charging time previously announced by the company
The measurements show that the Donut Battery can withstand astonishing charging rates even without active temperature control. Under the specified testing conditions, the cell was successfully charged at 5C for over nine minutes. At this charging power, the battery cell reached an 80% state of charge in about 9.5 minutes and a full 100% state of charge in just over 12 minutes. When discharged after charging, 100% of the charged capacity was available from the cell.
The battery cell was then recharged rapidly at the extreme speed of 11C. Charging from 0 to 80% was achieved in 4.5 minutes and a full 100% state of charge in just over seven minutes. When discharged after a full charge, 98.4 to 99.6% of the battery capacity was available for use.
Even though the testing conditions did not directly simulate cell behaviour in a battery pack, the measurement demonstrates the benefits of the Donut Battery as part of a pack as well. The battery cell does not require any particular compressive force and works well with passive cooling, which simplifies the battery pack architecture.
“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”, says Donut Lab CTO Ville Piippo.
The measurement report can be viewed in full on the I Donut Believe website.
For more solid-state battery technology news, click here.
