On October 14, 2026, NASA announced that small prototype cells of SPEARS, a solid-state battery it is developing for use on the Moon, operated down to -80°C in ground-based thermal vacuum tests. The cells were also undamaged after exposure to -170°C. However, the temperature at which a battery can operate is not the same as the temperature it can survive. To use batteries in the Moon's harsh cold, NASA is aiming for a system in which a chilled battery is warmed when needed and put back to work.
What the temperatures mean for operation and survival
In thermal vacuum tests at Langley Research Center, the small prototype cells performed well from 80°C down to -60°C, and still operated at -80°C with somewhat reduced performance. A thermal vacuum test examines how equipment behaves under combined vacuum and temperature conditions. The subjects here were small coin-type cells, so the result is not the same as testing a full battery pack mounted on a rover on the lunar surface.
Yi Lin, who leads the testing and research, explained: "This is the first demonstration that these cells can operate down to -80°C." That statement refers to the results for these prototype cells. The published article does not give a specific percentage for how much performance dropped at low temperatures.
NASA also reported that the battery showed no damage after being exposed to extreme temperatures from 100°C to -170°C. Separating "operated" from "undamaged after exposure" in NASA's announcement, the meaning of each temperature is as follows.
| Temperature | Result or condition shown by NASA | What can be read from it |
|---|---|---|
| 80°C to -60°C | Small prototype cells operated well | Operating result in thermal vacuum tests |
| -80°C | Operated with somewhat reduced performance | Rate of performance drop not stated in the published article |
| 100°C to -170°C | No damage after exposure | Does not mean the cells operate across this entire range |
| -200°C | Presented as a temperature reached during the lunar south pole's night | Not a temperature demonstrated for these cells |
The source is NASA's October 14, 2026 announcement. The table sorts the temperatures in the same announcement into operation, durability after exposure, and the expected environment; it is not a performance comparison between batteries.
-80°C is a confirmation of operation, while -170°C is a confirmation of durability after exposure. They are not the same performance metric. NASA also states clearly that even a solid-state battery will not operate while it is at -170°C. Keeping this distinction in mind rules out reading the result as a battery that can keep working through the lunar night without heating.
Note also that what has been published is NASA's introduction to the research, and it includes no link to a peer-reviewed paper. The number of cells tested, the test duration, and the number of times temperatures were cycled are not given, so it is too early to judge durability over long-term use.
Aiming for a battery that is warmed only when needed
SPEARS replaces the liquid electrolyte used in conventional batteries with a solid ceramic or polymer material. The electrolyte is the material that carries ions inside a battery. NASA cites as a problem that conventional liquid electrolytes can freeze in cold like that of the lunar night and damage the battery. There is also the problem that a liquid directly exposed to the vacuum of space would evaporate, and NASA's idea is to address such environmental challenges by making the material solid.
NASA explains that because solid electrolytes do not freeze the way liquids do, batteries can survive exposure to extreme cold. But to draw power again from a cell that has endured the cold, it must be brought back to a temperature at which it can operate. That is where a small heater comes in.
In the operation NASA envisions, the battery does not need to be kept warm all the time; it is warmed to operating temperature when it is used. The NASA-distributed article published on Phys.org also describes this approach to heating. If the burden of constant warming can be reduced, spacecraft and lunar habitats might rely less on heavy thermal management equipment.
In other words, a battery that tolerates cold is expected not only to lower the minimum temperature at which it operates, but also to reduce the need to keep it warm while idle. NASA cites possible benefits such as lighter weight, lower cost, and longer missions, but the announcement gives no figures for how much weight or power could be saved. How much the burden can be reduced for the whole system, including the heater, will be a practical criterion for judging it.
Testing that remains before use in lunar equipment
Applications envisioned for SPEARS include drills and rovers used in shadowed craters and emergency power for astronauts. Supplying power to long-running scientific instruments is also a candidate. NASA requires that the batteries avoid fire hazards and be safe to use, but the temperature tests alone do not guarantee safety under all conditions.
The plan is to tailor the batteries to each use by changing the electrode materials. Lin explains that stored energy, power output, and durability can each be adjusted. An observation instrument that needs to supply power for a long time and a tool that needs power during work call for different combinations of performance. The idea is to take solid-state construction as a common approach while building batteries suited to each use.
The project began in 2026 and is led by Glenn Research Center. Langley handles testing, and Ames Research Center is developing the substrates and electronics for tests in space. The early stage focuses on technology development, with possible commercial partnerships to follow. The announcement does not confirm adoption in lunar equipment or a launch date.
SPEARS evolved from earlier research aimed at aviation applications, and it also has potential uses on Earth in the future. NASA researchers name cars, mobile phones, and communications equipment as candidates. They anticipate broader use wherever portable power is needed, including drones, but there is no decision to put it in commercial products.
To become a power source that can be relied on on the Moon, the batteries will need verification of the power and time required to bring chilled cells back, as well as their performance under repeated use. If that verification and the development of space-qualified equipment advance, it could make concrete a design that reduces the burden of keeping batteries warm for protection and directs power toward observation and work.