A new temperature-aware charging protocol could help preserve the health of lithium-ion batteries used in Mars missions, where extreme and rapidly changing temperatures stress energy systems. In laboratory simulations that mimic Martian diurnal cycles, researchers demonstrated that adjusting charge parameters in real time according to battery temperature can reduce aging and improve usable capacity over long mission lifetimes.
What the study proposes
The central idea is to integrate a temperature-responsive charging strategy into the battery management system (BMS). By continuously monitoring cell temperature during charging and dynamically adjusting current and voltage steps, the protocol aims to minimize lithium plating at cold temperatures and excessive SEI growth at higher temperatures. The concept is especially relevant for small to medium-sized Li-ion packs used in landers, rovers, and habitats where power comes from solar arrays with limited energy margins.
How the temperature-aware protocol works
- Real-time temperature sensing: Temperature sensors across the battery pack feed data to the BMS.
- Adaptive charging current: The protocol reduces charging current when temperature drops toward the plating risk region, and increases it when safely heated, within safe voltage ceilings.
- Thermal-aware voltage management: End-of-charge voltage is adjusted depending on temperature to mitigate SEI thickening and gas formation.
- Preconditioning and delay strategies: If cells are very cold, charging may be delayed or preconditioned with gentle heating to avoid abrupt plating.
- Thermal management integration: The plan integrates with the spacecraft’s thermal system to balance heat generation from charging with external cooling capabilities.
- Energy-aware scheduling: Charging is aligned with solar availability to minimize periods of high-temperature stress from sun exposure.
Why this matters for Mars missions
On Mars, daylight and night cycles create broad and rapid temperature swings. Batteries must perform reliably for months or years while exposed to ambient conditions far colder than typical Earth environments. A charging scheme that adapts to temperature can prevent two common failure modes in Li-ion cells: lithium plating at low temperatures, which reduces capacity and increases safety risk, and accelerated SEI growth at higher temperatures, which steadily degrades capacity. By smoothing the aging process, the protocol can extend usable energy, maintain higher capacity retention, and reduce maintenance intervals for deep-space hardware.
Laboratory tests and key findings
Researchers evaluated the protocol on representative Li-ion chemistries typical for space hardware, including nickel manganese cobalt oxides and lithium iron phosphate cells, under temperature profiles that resemble Martian day-night cycles. Tests incorporated real-time temperature data and a BMS-like controller to implement adaptive charging. Key outcomes included:
- Reduced incidence of lithium plating during cold-start charging scenarios.
- Mitigation of rapid capacity fade observed in conventional charging when cells experience wide temperature swings.
- Preservation of charge acceptance after long periods of storage at suboptimal temperatures.
- Compatibility with existing BMS architectures, with a software update able to enable the temperature-aware mode.
Operational implications for spacecraft power systems
The protocol has several potential practical benefits for Mars missions and similar deep-space operations:
- Extended mission life: Slower degradation enables longer intervals between battery replacements or resupply missions.
- Improved reliability: Fewer anomalous charging events and safer start-up after storage or dormant periods.
- Better energy planning: More predictable remaining capacity and calendar life supports mission planning for power budgets.
- Reduced thermal load: By using existing thermal controls for charge heating, mission designers can optimize mass and power use.
Background: how temperature affects lithium-ion aging
Li-ion cells age through intertwined chemical and mechanical processes. At low temperatures, the electrolyte becomes more viscous and lithium plating can occur on the anode during charging, which permanently reduces capacity and can create safety risks. At higher temperatures, the solid electrolyte interphase (SEI) layer grows more rapidly, consuming lithium inventory and increasing internal resistance over time. Temperature also influences mechanical stresses from electrode expansion and contraction, potentially leading to microcracks. A charging protocol that respects these temperature-dependent dynamics seeks to keep cells in a “sweet spot” where reactions proceed efficiently without promoting damaging side effects.
Context within the broader space-battery program
Battery management systems for space hardware are already designed with safety margins and redundant sensors. The new approach complements these designs by adding an adaptive control layer that makes charging decisions in real time based on sensor data. If implemented across a fleet of rovers or habitats, the approach could standardize how charging is handled during different mission phases, from launch and transit to surface operations and decommissioning.
Challenges and considerations
Several hurdles must be addressed before widespread adoption:
- Sensor reliability in harsh environments: Temperature sensors and their readings must remain accurate over long missions with radiation exposure and vibration.
- Software robustness: The adaptive controller must fail-safe if sensor data are noisy or unavailable.
- Thermal coupling: In tightly packed packs, heating one cell may raise temperatures in adjacent cells; thermal modeling is needed to prevent hotspots.
- Validation on Earth: Ground tests require simulating Martian conditions and solar cycles, which can be expensive and time-consuming.
Future directions
Researchers see several avenues for extending the work. These include integrating machine learning with historical battery data to optimize charging profiles for specific chemistries, pack sizes, and mission profiles; exploring hybrid cooling strategies that combine passive insulation with targeted heating; and validating the protocol across a broader range of cell chemistries designed for space use. The team also plans to investigate how temperature-aware charging interacts with end-of-life indicators and battery health forecasting models used in mission control.
Conclusion
Temperature-aware charging represents a practical evolution in battery management for space missions. By aligning charging behavior with the real-time thermal state of lithium-ion cells, the approach aims to extend battery health, improve reliability, and enhance the feasibility of longer, more ambitious missions to Mars and beyond. While challenges remain in sensor durability, validation, and integration with thermal systems, the concept offers a clear path toward more resilient energy storage in harsh extraterrestrial environments.