Donut Lab demonstrated that their solid-state battery charges to 80 % in under five minutes during autonomous testing

Donut Lab publishes results of solid-state battery testing

Donut Lab has released a detailed report on the performance of its new solid-state battery system, confirming that it does not require a complex liquid cooling system. According to The Verge, during a series of tests the device charged from 0 % to 80 % in less than five minutes and retained 99 % of its capacity.

What the study proved
* The Finnish VTT state center conducted tests focusing on charging speed and thermal behavior of the module.
* The solid-state lithium‑ion battery (SSB) charges significantly faster than conventional Li‑ion batteries without losing capacity.

C‑rate metric
VTT engineers used the C‑rate indicator – charging rate expressed as a fraction of full capacity per hour (1 C = full charge in 1 h).
* Conventional Li‑ion batteries operate at 1–3 C and require active cooling.
* In Donut Lab tests, the battery was charged at 5 C (80 % in 9.5 min) and 11 C (full charge just over 12 min). After discharge, they showed that the battery delivers 100 % of stored energy, refuting concerns about instant chemical degradation at high currents.

Cooling tests
Most electric vehicles use liquid cooling systems. VTT removed them from the design and tested only passive heat dissipation:
1. The battery between two aluminum plates – excellent thermal conductivity, no overheating.
2. On a single metal surface – in one test the temperature reached 90 °C (the safety threshold), causing equipment shutdown. With increased contact to the surface, the heat sink worked normally.

Unique features of Donut Lab
* Does not require special compression and complex cooling systems, unlike other solid-state technologies where the battery under pressure can change volume by 15–20 %.
* This simplifies module design and makes it more cost‑effective at high energy density.

Specifications:
Parameter Value Energy Density 400 Wh/kg (vs. 200–300 Wh/kg for Li‑ion) Lifetime 100,000 cycles (vs. 1,500–3,000 for traditional tech) Sample Capacity V126 Ah, nominal energy 94 Wh

Alignment with industry expectations
* Earlier motorcycle manufacturer Verge stated that models with solid-state batteries could travel up to 600 km on a single charge.
* Charging to 80 % takes less than 10 min when connected to a 200 kW station – this makes electric transport competitive in convenience with internal combustion engines.

Remaining questions
VTT researchers did not analyze the cell’s chemical composition, relying on manufacturer data. Additionally, the report lacks a detailed analysis of long‑term stability and behavior under extreme operating conditions.