Why should lithium iron phosphate (LiFePO₄) batteries be stored at 40%–60% charge?

Avoid over-discharge (low power)

• When battery voltage drops too low (usually below 2.5V), it can cause:
• Irreversible chemical reactions inside the battery
• Electrolyte decomposition or plate damage
• Permanent capacity loss or even total failure
• Long-term storage at low power may also cause the battery to enter a “sleep” state, making it difficult to recharge.

Avoid storage at full charge

• Storing at 100% charge, especially in high temperatures, can lead to:
• Increased oxidation of the positive electrode material
• Accelerated electrolyte decomposition
• Higher risk of thermal runaway
• Faster battery aging

40%–60% is a stable chemical state

• In this range, the positive and negative electrodes remain in a relatively stable redox state, with minimal side reactions.
• The battery maintains low internal resistance and stable electrolyte pressure, making it ideal for long-term storage.