Lithium iron phosphate (lifepo4) batteries need to maintain a state of charge (SOC) of 50%±10% for long-term storage, and the ambient temperature should be controlled within the range of 15℃±5℃. The 12-year tracking data of the United States Naval Research Laboratory shows that the average annual capacity attenuation of lifepo4 with fully charged (100% SOC) storage is 3.2%, while that of the 50% SOC storage group is only 0.8%. The attenuation rate of high-temperature storage at 40℃ is four times faster than that in an environment at 25℃ (4.7% vs 1.2%/ year). Tesla’s spare parts warehouse adopts a constant temperature and humidity system (temperature 15℃±1℃, humidity 45%±5%). After five years, the battery capacity retention rate is 94.3%, and the voltage deviation is less than 0.02V.
Humidity and packaging standards determine the safety boundary. The UL 1973 certification requires that the relative humidity of the storage environment be ≤60%, the battery terminals need to be coated with antioxidant grease (with a thickness of 0.2mm), and the salt spray test of metal parts should be ≥96 hours. The analysis of the warehouse accident in Dongguan in 2023 pointed out that the humidity in coastal areas exceeding 70% led to terminal corrosion (an increase of 18mΩ in resistance), causing local overheating. Catl’s solution adopts vacuum aluminum-plastic film encapsulation (water and oxygen transmission rate <0.005cc/m²/day), combined with a desiccant (moisture absorption capacity 30g/unit), extending the storage safety period to 10 years.
Regular maintenance strategies affect life cost. Capacity calibration is required every six months: discharge at a rate of 0.2C to 2.5V and then charge to 3.45V (voltage accuracy ±0.5%). Data from Bosch’s energy storage factory in Germany confirmed that the median capacity of calibrated lifepo4 stock batteries was 98.5Ah (labeled as 100Ah) after five years, while that of the uncalibrated group dropped to 91.2Ah. Calibration takes approximately 8 hours per batch, but reduces the capacity dispersion to <3% (15% for the unmaintained group), which is equivalent to extending the service life by 32%.
Economic optimization relies on intelligent monitoring. The annual monitoring cost of a single battery equipped with an Internet of Things sensor (with temperature accuracy ±0.3℃ and voltage sampling ±5mV) is 1.2, which is 83,280,000 lower than the replacement cost of manual inspection.
Secure storage needs to avoid extreme conditions. Storage below -20℃ will cause the electrolyte to solidify (freezing point -40℃), and the internal resistance will increase by 300%. The environment of >45℃ accelerates the thickening of the SEI film (with a growth rate of 0.8nm/ month). The traceability of the 2022 warehouse fire in Dubai revealed that lifepo4 batteries stacked more than three layers (with a bottom pressure resistance of over 200kg/m²) caused an internal short circuit due to shell deformation. Industry standards require that the load-bearing capacity of storage racks be ≥500kg/m², the spacing be ≥10cm, and the temperature variation rate be <5℃/h.
Future technologies will rewrite the storage rules. The solid electrolyte lifepo4 (patent CN20241088006.X) mass-produced by CATL in 2025 has a capacity retention rate of over 99% after being stored at 30℃ for 10 years, and its self-discharge rate drops to 0.1% per month. The EU Battery Passport standard requires blockchain evidence storage of data to achieve a 37% reduction in the carbon footprint throughout the entire life cycle.