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1Clear out junk files and repair common Windows errors2Scan for outdated or missing drivers - takes under a minute3Repair Windows errors before they cause bigger problemsVTT’s first Donut Lab test showed that one customer-supplied cell identified as solid-state could charge rapidly under controlled laboratory conditions. VTT measured a nominal 26 Ah capacity, about 9.5 minutes to 80% at 5C, and roughly 4.5–4.9 minutes to 80% in the completed 11C tests. Those results describe that cell and that procedure—not a verified battery chemistry, production-ready vehicle pack, 400 Wh/kg design, or 100,000-cycle life.
What VTT tested
Report VTT-CR-00092-26, Donut Lab Solid-State Battery V1 Charge Performance Test, is dated 9 February 2026. VTT’s stated objective was to measure charging performance of energy-storage devices supplied by the customer and identified by that customer as solid-state cells.
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The report says the same single cell was used throughout the work and that the customer supplied the test plan. VTT did not independently identify the cell’s electrolyte, electrodes or other active materials in this charging report.
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- Instrument: PEC ACT0550 battery tester.
- Environment: climate chamber.
- Thermal configurations: one-sided or two-sided heat sinks; the cell was not in direct contact with the heat sinks.
- Nominal capacity: 26 Ah, determined in an initial capacity test.
- Charge currents: 130 A at 5C and 286 A at 11C.
Charge procedure
- VTT discharged the cell at 1C to 2.7 V before a fast-charge run.
- It charged at constant current until the cell reached 4.3 V.
- It then held 4.3 V in constant-voltage mode until the target charge capacity was reached.
- VTT discharged the cell again at 1C to 2.7 V after the fast-charge work to reset the test condition and measure capacity.
How fast did the cell charge?
The completed runs produced the following times. Each row is a cell-level measurement, not a vehicle charging promise.
#1 Best Overall
| Charge rate and target | Two heat sinks | One heat sink | What was recorded |
|---|---|---|---|
| 5C to 80% | 573 seconds (9.55 minutes) | 569 seconds (9.48 minutes) | Completed |
| 5C to 90% | 677 seconds (11.28 minutes) | 642 seconds (10.70 minutes) | Completed |
| 5C to 100% | 813 seconds (13.55 minutes) | 735 seconds (12.25 minutes) | Completed |
| 11C to 80% | 293 seconds (4.88 minutes) | 267 seconds (4.45 minutes) and 276 seconds (4.60 minutes) | Completed runs |
| 11C to 100% | 477 seconds (7.95 minutes) | 438 seconds (7.30 minutes) in the later run | One earlier one-sided run was interrupted before completion |
In practical terms, the tested cell reached 80% in approximately 4.5 minutes in the reported 11C runs. A completed 11C run took about 7.3–8.0 minutes to reach 100%, so the first report did not demonstrate a five-minute full charge.
What the charging result does—and does not—prove
What it does show
The VTT procedure is evidence that this particular 26 Ah cell accepted the stated currents and reached the reported charge targets with the listed heat-sink arrangements. It also documents the voltage limit, constant-current/constant-voltage sequence and discharge checks needed to interpret the timing.
What it does not show
- Chemistry: the report used the customer’s identification of the cell as solid-state; it was not a composition assay.
- Production consistency: one cell cannot establish variation across manufacturing batches or suppliers.
- Vehicle-pack performance: the setup was not a complete motorcycle or car pack, and the electrical, thermal and control limits of a pack were not tested.
- Cycle life: these charge runs were not a long-term aging study and do not validate a 100,000-cycle claim.
- Energy density: the charge report does not establish 400 Wh/kg or any other gravimetric or volumetric density.
- Safety in all conditions: it does not establish universal resistance to abuse, crashes, overheating or manufacturing defects.
- Cold-weather operation, cost or production volume: none was established by this report.
Donut Lab’s own first-results announcement acknowledged that the test conditions did not directly simulate behavior in a battery pack. Its January launch claims were broader than the measurements in VTT-CR-00092-26.
How the later results change the picture
Donut Lab and VTT subsequently publicized tests that address different questions. They should not be treated as additional pages of the original charge test or as a single certification package.
Rank #3
High-temperature performance
VTT report VTT-CR-00124-26, Donut Lab Solid-State Battery V1 High Temperature Performance Test, dated 2 March 2026, covered testing at 80°C and 100°C. Donut Lab’s summary says the cell delivered 110% and approximately 107% of its room-temperature nominal capacity under those discharge conditions. The 100°C test also saw the outer pouch lose vacuum. Those capacity interpretations come from the company’s summary; the pouch result is a separate observation from that experiment.
Ten-day charge-retention test
In a 9 March 2026 announcement, Donut Lab described charging a cell to approximately 50% and leaving it connected to a tester at room temperature for ten days, while voltage was monitored every ten seconds. The company says a final capacity measurement showed that the voltage change corresponded to remaining energy and interprets this as evidence of battery-like behavior rather than a supercapacitor. This was not a complete self-discharge map across storage temperatures, states of charge or longer periods.
Rank #4
Damaged-cell cycling
Donut Lab’s 23 March 2026 summary says the pouch that lost vacuum during the high-temperature work was then cycled five times at 1C, 50 times at 5C and five final times at 1C. The company reports capacity stabilizing at about 11 Ah from an initial approximately 25 Ah during the fast cycles, with no temperature spikes or fire in that test. The bounded conclusion is continued operation at reduced capacity in that single-cell experiment, not blanket proof of complete battery safety.
Pack-level charging demonstration
On 16 March 2026, Donut Lab announced a fast-charge demonstration with Verge Motorcycles using an air-cooled TS Pro battery pack. This is a different test scale from VTT’s original single-cell work. It supports the existence of a publicized pack demonstration, but does not establish fleet reliability, long-term degradation or broad production availability.
Energy-optimized cell
Donut Lab said on 2 September 2026 that VTT measured 409 Wh/kg and 805 Wh/L for an energy-optimized cell. The company described its chemistry as the same as in earlier tests, while also making clear that this was a different optimized cell. Those figures therefore should not be silently substituted for the original 26 Ah test cell or treated as a result of the first charge report.
Elemental analysis and chemistry claims
On 23 September 2026, Donut Lab summarized Intertek elemental analysis of a next-generation cell, reporting 3.4 parts per million of lithium and 632 parts per million of sodium. Donut Lab interprets those figures as excluding lithium-ion and sodium-ion chemistry. Because the underlying Intertek report, including its sampling and analytical context, was not available here, the concentrations and interpretation should remain attributed to Donut Lab rather than presented as a complete independent explanation of the cell’s chemistry.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.How to read Donut Lab’s headline claims
Donut Lab’s 5 January 2026 launch announcement claimed 400 Wh/kg, a full charge in five minutes, up to 100,000 cycles and use in Verge motorcycles. CEO Marko Lehtimäki said: “At Donut Lab, our answer on solid state batteries being ready for use in OEM production vehicles is now, today, not later.” The VTT charge report supports a narrower statement: one tested cell charged quickly under specified conditions. Each launch claim requires its own measurement, sample definition and repeatability evidence.
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| Claim or result | Evidence type | Proper scope |
|---|---|---|
| About 4.5 minutes to 80% at 11C | VTT cell-charge measurements | Completed runs on one cell with stated cooling and voltage limits |
| Five-minute full charge | Donut Lab launch claim | Not demonstrated by the completed full-charge runs in VTT-CR-00092-26 |
| 400 Wh/kg | Donut Lab launch claim | Not measured in the first charge report |
| 409 Wh/kg and 805 Wh/L | VTT results as reported by Donut Lab | Different, energy-optimized cell |
| Up to 100,000 cycles | Donut Lab launch claim | Not a result of the first charge test |
What evidence would settle the remaining questions?
A stronger production-readiness case would need independently documented chemistry, repeated cells from multiple production batches, full-pack charging with vehicle-relevant cooling and controls, abuse and fault testing, and long-duration cycling with defined capacity-retention criteria. Comparisons should keep these variables aligned:
- cell versus pack measurement;
- the same cell version versus a later optimized design;
- 80% versus 100% state of charge;
- C-rate, current, voltage ceiling, temperature and cooling arrangement;
- single demonstration versus repeated-cycle aging and batch variability;
- Wh/kg versus Wh/L; and
- independent measurements versus a company’s interpretation.
Source and quotation note
VTT-CR-00092-26 names Jari Haavisto and Ari Hentunen as authors. The report states that use of VTT’s name in advertising or publication of report excerpts requires written authorization. Donut Lab summaries are useful for identifying later demonstrations, but their statements should remain attributed to the company where the complete underlying report is not available.
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