- Donut Lab's battery module retains about 93% energy at -30°C.
- The module experiences limited amp-hour capacity loss, retaining about 97%.
- The module requires no external heating or insulation materials, demonstrating its technological potential.
- Donut Lab is focusing on the development of next-generation battery technology.
The battery module developed by Finnish technology company Donut Lab successfully retains about 93% of its energy at -30 degrees Celsius (-22 degrees Fahrenheit) without the need for external heating or insulation, according to the latest test results from VTT. The test was conducted on a complete module containing 14 first-generation Donut Battery cells. The 14-cell module provided 1,254 watt-hours of energy at -30°C, compared to 1,354 watt-hours at 25°C (77°F).
The module also retained about 97% of its amp-hour capacity, indicating limited capacity loss under the test conditions. These results address a significant challenge faced by electric vehicles, which typically provide less usable energy in cold weather. Low temperatures slow down the chemical reactions inside the battery and may reduce its power output.
Performance in Low Temperatures
Donut Lab focuses on developing battery technology for electric transportation applications and previously claimed that its batteries could retain 99% of their capacity at -30°C, although the latest test data is slightly lower than that figure. The module tested by VTT contained 14 first-generation Donut Battery cells, rather than evaluating a single cell. The module operates at a rated voltage of 48 volts and includes a small battery management system, with no heating elements, insulation materials, cooling equipment, or other thermal management systems. Researchers first tested its performance at 77°F, discharging at a rate of 1C, which corresponds to drawing its rated capacity in about one hour.
The module provided 27.77 amp-hours and 1,354 watt-hours of energy.
Subsequently, researchers lowered the temperature to -30°C (-22°F) and left the module for five hours. Internal and external sensors confirmed that the internal temperature of the module reached the target. Researchers conducted another discharge test at the same 1C rate, resulting in the module providing 26.8 amp-hours and 1,254 watt-hours. The difference between capacity and energy retention is significant. Amp-hours measure the amount of charge a battery provides, while watt-hours consider both charge and voltage. The module retained 97% of its charge capacity, but due to further voltage drop during discharge in cold conditions, it only provided about 93% of the original energy.
Potential for Future Technologies
According to Donut Lab, the battery still warms up during the discharge process despite the extremely low ambient temperature. The company stated that using an insulated battery casing could retain more heat, thereby improving performance. Ville Piippo, the company's Chief Technology Officer, said, "We intentionally eliminated all potential advantages that a battery might typically have." The company also reported that the module continued to charge and discharge normally after low-temperature testing, with no adverse effects observed. However, these results come from controlled experiments on a single battery module rather than a complete electric vehicle, making it unclear how much driving range an electric vehicle equipped with this technology could retain in cold conditions.
This cold weather assessment summarizes a series of tests conducted by VTT on Donut Lab's first-generation batteries. Previous evaluations examined five-minute charging, performance at 100°C, self-discharge, swelling, pressure, and energy density, among others. Donut Lab stated that it is now focusing on next-generation battery technology and plans to conduct further system-level demonstrations. The company's low-temperature test report has been made publicly available through its testing website.
Item Specification Module Voltage 48 volts Discharge Amp-Hours 26.8 amp-hours Discharge Watt-Hours 1,254 watt-hours
Breakthroughs and Challenges in Donut Lab's Battery Technology
Donut Lab's battery module retains most of its energy in extremely low-temperature environments, which is crucial for the practicality of electric vehicles. Low temperatures typically affect battery performance, leading to a decrease in usable energy, posing a significant challenge for electric vehicles used in cold regions. The company's design, which requires no additional heating or insulation materials, demonstrates the innovation of its technology. However, these tests were conducted on a single module, and the actual performance in electric vehicles still needs further validation. Donut Lab's future technological developments may change the performance of electric vehicles in various environments.