The nominal voltage of a single cell of lithium iron phosphate (lifepo4) is 3.2V, and the working voltage range is usually 2.5V to 3.65V. The voltage of the charging and discharging platform is stable at 3.2V±0.05V (fluctuation <1.5%), which is much lower than the 3.7V nominal voltage of ternary lithium batteries. According to the test data of IEEE standard 1625-2008, when lifepo4 is charged and discharged at a rate of 0.5C in an environment of 25℃, the proportion of the flat area in the voltage curve exceeds 85% (only 60% for ternary batteries), and the voltage fluctuation amplitude is ≤50mV. This characteristic significantly reduces the regulation complexity of the battery management system (BMS). According to the mass production data of CATL, the standard deviation of voltage consistency of its lifepo4 cells is controlled within 8mV, the voltage range of the module after grouping is ≤0.1V, and the voltage attenuation rate after 2000 cycles is less than 3%.
Temperature has a significant impact on voltage performance: At a low temperature of -20℃, the discharge cut-off voltage of lifepo4 drops to 2.8V (a 12.5% decrease compared to 25℃), and the capacity decays by 40%. At a high temperature of 60℃, the float charging voltage offset rate is ≤2%. Byd’s Blade Battery (lifepo4 technology) enhances the low-temperature voltage stability at -30℃ to 90% through nano-scale phosphorus-iron cathode materials, supports 2C rate (7.4kW) pulse discharge, and keeps the voltage drop within 5%. UL laboratory tests in 2023 show that when lifepo4 is overcharged to 5V, only electrolyte decomposition occurs (gas escape <0.1L/Ah), with no risk of thermal runaway, while ternary batteries trigger a chain reaction at 4.3V.
Practical application verification of voltage reliability: The Tesla Megapack energy storage system uses lifepo4 cells (3.2V per cell), with 384 cells connected in series to form a 1228V high-voltage system. The voltage sampling error is less than ±0.5%, and the system efficiency reaches 94%. In the comparative experiment, the median voltage of the lifepo4 battery pack remained at 3.18V after 1000 cycles, while the voltage of the NMC battery dropped to 3.52V under the same working conditions (attenuation rate 4.9%). The German TUV certification shows that the capacity recovery rate of the lifepo4 module is over 95% after being over-discharged to 2.0V, and the voltage rebound delay is less than 10 milliseconds. It is suitable for grid frequency regulation (response frequency 0.1-10Hz).
In terms of cost-effectiveness, the voltage characteristics of lifepo4 reduce the difficulty of system integration: A 12V car start-stop battery only requires 4 strings (3 strings for a ternary battery), reducing the BMS cost by 20%. The 48V home energy storage system consists of 15 battery cells connected in series, with the voltage tolerance band narrowed to ±1%, and the energy utilization rate increased by 35% compared to lead-acid batteries. According to Bloomberg New Energy Finance, the global lifepo4 production capacity will exceed 800GWh in 2024. The large-scale production has raised the voltage qualification rate of individual cells from 98.2% to 99.5%, and the average price of cells has dropped to $0.08/Wh (a 67% decrease compared to 2019).