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Generally, the upper limit voltage of lithium iron phosphate battery charging is 3.7~4V, and the lower limit voltage of discharging is 2~2.5V. Considering discharge capacity, discharge median voltage, charging time, constant current capacity percentage, and safety, constant current and constant voltage are adopted. For lithium iron phosphate batteries, it is reasonable to set the charging limit voltage at 3.55~3.70V (recommended: 3.60~3.65V), with a discharge lower limit voltage of 2.2V~2.5V.

The lithium iron phosphate battery is designed for a 3.6V charging limit, allowing full activation of capacity without damaging the battery.

The number of charging times refers to the number of complete charge and discharge cycles. Although a 3.4V design avoids overcharging, a small number of cells may not participate in the cycle, leading to performance degradation over repeated cycles until the battery can no longer be used. This is due to the unavoidable accumulation of harmful and unfavorable factors, which eventually prevent the performance from maintaining the original design parameters.

Although lithium iron phosphate battery packs are designed with voltage limits and equipped with protection boards to prevent overcharging, using the correct charging method is also essential for prolonging the battery lifespan.

Lithium Iron Phosphate Battery Safety

When buying new energy vehicles, people often choose between lithium iron phosphate batteries and ternary lithium batteries. Industry insiders typically advise:

• Ternary system: Better for those focusing on battery life and lightweight vehicles.
• Lithium iron phosphate: Emphasizes safety.

So, are lithium iron phosphate batteries safe? This can be evaluated from three aspects: material/structural stability, production process, and charge-discharge characteristics.

1. Material and Structural Stability

Lithium iron phosphate is currently the safest cathode material for lithium-ion batteries, containing no harmful heavy metals. Its olivine structure makes it difficult to precipitate oxygen, improving material stability.

2. Production Process

The production process of lithium iron phosphate batteries is similar to other lithium batteries: batching, coating, rolling, filming, and winding. Due to lower conductivity, lithium iron phosphate particles are made smaller, resulting in a more uniform internal arrangement and promoting a balanced voltage platform, ensuring stable battery operation.

3. Charge and Discharge Characteristics

Charging and discharging are the two basic working states of lithium batteries. During these processes in lithium iron phosphate batteries, the weak oxidation ability of iron ions prevents oxygen release, reducing the chances of redox reactions with the electrolyte and ensuring safety during operation.

Even under high-rate discharge or overcharge conditions, lithium iron phosphate batteries rarely undergo severe redox reactions. Additionally, after lithium deintercalation, the reduced unit cell volume offsets the increased volume of the carbon negative electrode, maintaining structural stability and eliminating risks of bursting due to volume expansion.

Battery Pack Safety

The above explanations are based on single cells. In practical use, lithium iron phosphate batteries need to be assembled into packs to provide rated voltage and capacity. This involves series/parallel or serial-parallel configurations, with consistency of each cell being critical. A balanced management system is typically included to control key parameters, ensuring safety during use, which is common across all lithium battery packs.