Key points for maintaining lithium batteries when they are out of use for a long time

When lithium battery packs are not in use for a long time, systematic maintenance measures should be taken to prevent capacity attenuation, performance deterioration and safety hazards. The following analysis is conducted from five dimensions: preparations before shutdown, environmental control, power management, regular maintenance, and safety protection:

First, preparations before discontinuation

Power status adjustment

Recommended SOC range: Adjust the battery pack's charge (SOC) to 40% to 60%. This range can balance the self-discharge rate and the risk of over-discharge, avoiding the accelerated decomposition of the electrolyte caused by fully charged (100% SOC) storage or the over-discharge damage caused by low-charged (<20% SOC) storage.

Balancing processing: If the battery pack supports active balancing function, balancing should be initiated before deactivation to reduce the capacity difference between individual cells and prevent the capacity imbalance from worsening after long-term deactivation.

Health status detection

Key parameter detection: Measure the total voltage of the battery pack, the voltage of individual cells, internal resistance and insulation resistance to ensure there are no abnormal voltages of individual cells (such as voltage difference >50mV) or insulation failure issues.

Fault isolation: If performance degradation or faulty modules are detected, they should be replaced or isolated in advance to avoid affecting overall performance.

Physical protection

Prevent mechanical damage: Place the battery pack in a dedicated shockproof and pressure-resistant bracket or packaging box to avoid internal short circuits caused by external force compression during storage.

Moisture-proof and dust-proof: Use moisture-proof bags (such as aluminum foil bags) to encapsulate the battery pack and add desiccants to prevent moisture from entering and causing corrosion or short circuits.

Second, environmental control

Temperature management

Recommended range: The storage temperature should be controlled between 15℃ and 25℃. Excessively high temperatures will accelerate the internal side reactions of the battery (such as thickening of the SEI film), leading to irreversible capacity decline. If the temperature is too low, it may increase the viscosity of the electrolyte, affecting the migration efficiency of lithium ions.

Extreme temperature avoidance: Avoid exposing the battery pack to environments above 40℃ or below -20℃. If this cannot be avoided, shorten the maintenance cycle (for example, from once every 6 months to once every 3 months).

Humidity control

Relative humidity requirement: The humidity of the storage environment should be below 60%. High humidity can easily cause corrosion of battery casings, oxidation of interfaces, and even internal short circuits.

Dehumidification measures: In a humid environment, dehumidifiers should be configured or hygroscopic materials (such as silica gel desiccants) should be used to maintain low humidity.

Ventilation and cleanliness

Ventilation requirements: The storage space must be well-ventilated to prevent the accumulation of flammable gases (such as organic solvents produced by the evaporation of the electrolyte).

Cleanliness: Avoid exposing the battery pack to dust and corrosive gases (such as chlorine and hydrogen sulfide) to prevent damage to the casing and electrical interfaces.

Third, electricity management

Self-discharge compensation

Compensation cycle: The self-discharge rate of lithium battery packs is approximately 2% to 5% per month. The battery packs need to be charged once every 3 to 6 months to restore the SOC to 40% to 60%.

Compensation method: Use a charger that matches the battery pack and charge in constant current - constant voltage (CC-CV) mode to avoid overcharging or undercharging.

Long-term deactivation threshold

Avoid deep discharge: If the battery is not in use for more than one year, the SOC of the battery pack should be adjusted to around 50%, and the maintenance cycle should be shortened to once every three months to prevent over-discharge due to self-discharge.

Fourth, regular maintenance

Performance recheck

Inspection items: Conduct a comprehensive inspection of the battery pack every 6 to 12 months, including capacity, internal resistance, insulation resistance and charge and discharge efficiency.

Data recording: Establish a storage file, record the data from previous tests, and predict changes in battery performance through trend analysis.

Inspection of connecting parts

Electrical connection: Check whether the positive and negative terminal blocks of the battery pack are loose or oxidized. Tighten or clean them if necessary.

Communication interface: Confirm that the BMS (Battery Management System) communication interface is free from corrosion or foreign objects to ensure normal data transmission.

Environmental adaptability inspection

Temperature and humidity calibration: Regularly inspect the temperature and humidity monitoring equipment in the storage environment to ensure the accuracy of the data.

Ventilation system maintenance: Clean the ventilation ducts and filters to prevent dust from blocking and affecting air circulation.

Fifth, safety protection

Fire and explosion prevention

No Smoking or open flames: Open flames, smoking and the use of equipment that can produce sparks are strictly prohibited in the storage area.

Fire protection configuration: Dry powder fire extinguishers, carbon dioxide fire extinguishers or heptafluoropropane fire extinguishing systems should be provided. Water-based fire extinguishers should be avoided.

Short-circuit protection

Insulation treatment: The positive and negative terminals of the battery pack should be protected with insulating rubber sleeves or terminal covers to prevent contact with metal foreign objects.

Storage distance: At least 0.5 meters should be maintained between battery packs to facilitate heat dissipation and emergency handling.

Emergency response plan

Leakage handling: If electrolyte leakage is detected, protective equipment (such as acid and alkali resistant gloves and goggles) should be worn for cleaning, and the leaked substance should be adsorbed with sand or vermiculite.

Thermal runaway response: If the battery pack shows signs of thermal runaway such as smoke or fire, the power supply should be immediately cut off, the fire extinguishing system activated and personnel evacuated.