Does the Donut solid-state battery really work? Independent laboratory tests support specific claims about particular samples: VTT measured 409.3 Wh/kg in one energy-optimized V1.5 cell and separately recorded rapid charging and charge retention in V1 cells. Those tests do not establish that one cell delivers every advertised feature, verify the 100,000-cycle claim, or identify the full chemistry. The distinction between cell generations, samples, and test conditions is essential to judging what the results show.
Does the Donut solid-state battery really work?
There is credible evidence that the tested Donut cells function as energy-storage devices and can deliver some of the measured performance reported for them. But “the battery works” can mean several different things: a cell can charge and discharge, meet an energy-density figure, survive a defined abuse test, last through a specified number of cycles, or perform reliably in a production vehicle. Evidence for one does not establish the others.
Donut Lab announced on 5 January 2026 that its all-solid-state battery was ready for original-equipment-manufacturer vehicle manufacturing. The company advertised 400 Wh/kg, charging in as little as five minutes, a design life of up to 100,000 cycles, extreme-temperature performance, and use in Verge motorcycles. Those were company claims, not findings contained in the announcement itself. Donut Lab 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 independent results available by October 2026 are narrower. VTT Technical Research Centre of Finland tested V1 cells for charging and charge retention, then measured energy density on a separate, energy-optimized V1.5 cell. Intertek examined other supplied samples for structure and elemental content. Because the tests concern different generations and samples, their results cannot be combined into a single demonstration that one cell has all the reported properties.
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Has the 400 Wh/kg claim been independently verified?
For one specified cell, yes. VTT report VTT-CR-00391-26, dated 1 September 2026, reports 409.3 Wh/kg and 804.7 Wh/L for a Donut Battery V1.5 cell designated DL6. VTT described it as an energy-optimized variant. The measurement was based on the cell’s measured mass, dimensions, and capacity; the cell was discharged at 0.1C and 25°C within its recommended 2.3–4.25 V range.
This is a cell-level result, not a pack-level measurement or proof that every Donut cell—or a motorcycle battery pack—has the same energy density. VTT says the customer supplied the device and the work followed the customer’s test plan. The report provides a meaningful measurement of that sample under the stated conditions; it does not establish production yield, cost, or performance across a fleet.
Earlier coverage in March 2026 said an independent energy-density measurement was not then available. That description was accurate at the time but was superseded by VTT’s September V1.5 result. It remains important not to confuse that later measurement with the earlier V1 charge-test cells.
Can it really charge in five minutes?
VTT’s V1 testing supports very fast cell charging, but “80% in under five minutes” and “full in five minutes” are different claims. Report VTT-CR-00092-26 describes tests on one customer-supplied 26 Ah cell. VTT used current-then-constant-voltage charging, reporting 5C as 130 A and 11C as 286 A. The report considered one- and two-sided heat-sink arrangements.
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| Charge rate | Time to 80% | Time to 100% | What the result means |
|---|---|---|---|
| 5C (130 A) | 569–573 seconds | 735–813 seconds | VTT’s reported V1 cell-level test times. |
| 11C (286 A) | 267–293 seconds | 438 and 477 seconds in completed runs | VTT’s reported V1 cell-level test times; the completed full-charge runs took longer than five minutes. |
One 11C attempt using a single heat sink was stopped after the cell surface reached the 90°C safety limit. The report describes improved heat transfer and a later run. The results therefore show that a particular cell reached 80% in roughly four and a half to just under five minutes in the reported 11C runs, while completed runs to 100% took more than seven minutes. They do not establish a five-minute full charge for a motorcycle or car: vehicle charging depends on the pack, cooling system, charger, operating limits, and the definition of “full.”
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What is the battery made of?
The available reports do not disclose the complete chemistry of the V1.5 cell whose energy density VTT measured. VTT’s earlier charging report says the customer identified its supplied devices as solid-state battery cells; the charging test measured charging performance, not chemical composition.
Intertek report 2608094STO-003 examined two supplied devices by destructive visual teardown. It found a layer arrangement consistent with a bipolar stack design, but stated that it had not verified the devices were functioning cells that could be charged or discharged. A structural observation can describe how layers are arranged; it does not identify the electrolyte or establish the full electrochemistry.
A separate Intertek Wilton report, IWTN/W000020339RLM002, dated 22 September 2026, used ICP-OES to measure lithium and sodium in active components from one teardown sample identified as the same item referenced in the bipolar report. It reported 3.4 ppm lithium and 632 ppm sodium in the included anode, cathode, and current-collector parts. Donut Lab interprets these levels as evidence against lithium-ion or sodium-ion chemistry. The elemental measurements alone do not identify the complete chemistry, establish the electrolyte, or show that the V1.5 cell had the same composition.
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The independent tests described here do not establish a 100,000-cycle service life for a healthy cell. Donut Lab’s product page advertises up to 100,000 cycles, but that company specification should not be treated as a result of the VTT charging, energy-density, or retention tests.
Donut Lab’s March 2026 account of a VTT test describes a damaged-cell demonstration, not a lifetime test. The cell had suffered damage during an earlier high-temperature test when its vacuum structure failed. It then completed five 1C cycles and 50 cycles at 5C. During the fast-charge cycles, its capacity settled at about 11 Ah, compared with an initial 25 Ah, with some recovery during five final 1C cycles. Donut Lab explicitly said this was not a battery life-cycle test. It cannot verify how many cycles a healthy cell can complete before reaching an end-of-life threshold.
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That test series also included safety claims about the damaged cell and Intertek nail-penetration testing on a next-generation cell. Such results apply to their defined samples and test configurations; they do not establish how every cell or pack will respond to all crashes, abuse, thermal events, or failure modes.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.What does the charge-retention test show?
VTT report VTT-CR-00125-26 gives limited evidence about idle-period charge retention in a V1 sample. VTT recorded an initial measured capacity of 26.5 Ah, charged the sample in stages to about 50% state of charge, left it idle for 240 hours at 22–28°C, and then measured discharge. The cell delivered 97.7% of the charged capacity after that interval.
This result is evidence that the tested sample did not rapidly lose most of its charge over ten days under those ambient conditions. It is not a general shelf-life result, nor does it answer how the cell ages over months or years, at other temperatures, or through repeated use.
Is it in production motorcycles yet?
Donut Lab has described Verge motorcycle applications, but vehicle application claims and cell-laboratory measurements are separate evidence categories. Donut Lab’s test archive describes a Verge pack-level charging session as a customer system-validation demonstration, not a VTT test. The archive identifies the pack as an 18 kWh nominal, air-cooled previous-generation mule-bike pack. That is a company-described demonstration; it does not independently verify the VTT cell results or establish that the same charging performance applies to consumer motorcycles.
The reviewed sources do not independently establish completed consumer deliveries, audited production volume, or that advertised vehicle range and charge rates apply to all delivered bikes. A cell result cannot by itself establish the performance of a complete pack in a production vehicle. For that, useful evidence would include documented serial deliveries and representative pack-level results in real operating conditions.
How should the claims be judged?
Read each number alongside the sample, generation, test method, and source. VTT’s V1 charging and retention results and V1.5 energy-density result are distinct measurements. Intertek’s teardown findings concern other samples and answer structural or elemental questions, not cell performance. Donut Lab’s specifications and vehicle descriptions remain company statements unless a specified independent test supports the particular claim.
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- Measured for a defined sample: V1.5 energy density, V1 fast charging, and V1 charge retention, each under the conditions stated above.
- Not established by these tests: 100,000-cycle life for healthy cells, full V1.5 chemistry, fleet-wide production performance, or universal five-minute full charging.
- Still needed to resolve the largest gaps: a published long-duration cycle test on healthy cells and a complete chemistry report tied to the V1.5 sample.
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