The practical usable energy of a LiFePO4 battery with a nominal capacity of 2560Wh is heavily influenced by depth of discharge (DoD), efficiency loss, and temperature. In the regular environment of 25℃ and 90% DoD, its effective energy storage is measured at 2304Wh (nominal value ×90%×0.95 coulomb efficiency), which is 111% greater than the 1088Wh capacity of lead-acid batteries of the same spec (nominal value ×50% DoD×0.85 efficiency). For instance, consider the CATL EnerC 2560Wh battery pack. Its discharge feature is that when it has a load of 1C rate (2.56kW), the actually discharged energy is 2422Wh (94.6% of nominal capacity), the voltage fluctuation range is controlled within 51.2V±0.8V (±2.5V for lead-acid battery), and the loss of energy conversion is only 5.4%.
Temperature has a great impact on actual energy storage: In a low-temperature condition of -20℃, the capacity of LiFePO4 batteries decreases to 2048Wh (80% of nominal value), but the capacity can also be restored to 89% (2278Wh) by using self-heating technology (12W power consumption). The 2023 measurement data from the Norwegian Northern Lights Observatory shows that the photovoltaic system with 2560Wh LiFePO4 batteries has an average daily power supply of 18.2kWh during winter (average temperature -15℃), a 95.7% increase compared to the lead-acid system (9.3kWh). Under the high test temperature of 45℃, after 1000 cycles the capacity retention ratio of this battery was 92.5% (2368Wh), whereas for lead-acid batteries the figure was far lower at 58% (1485Wh).
The divergent application occasions bring about unstable energy utilization rates. In a home energy storage system, due to the inverter efficiency loss (average value 93%), the actual output available energy of a 2560Wh lifepo4 battery is 2147Wh (2560×90% DoD×93%). However, if it is used to supply DC load devices (such as LED lighting), the efficiency can be increased to 98%, and the energy released can be as high as 2258Wh. Tesla Powerwall customer data shows that its 2560Wh battery pack, when operating in off-grid photovoltaic mode, has an average of 0.7 cycles per day and an annual degradation rate of only 0.8%. Its total stored energy over its entire life cycle (4,000 cycles) is 8.19MWh (2560Wh×4000×0.9 DoD×0.92 average retention rate).
In cost-effectiveness, calculated at a cost of 0.15 per Wh, purchasing a 2560WhLiFePO4 battery costs 384, while the LCOE cost of Electricity per kilowatt-hour throughout its lifespan is 0.047/kWh (384 ÷ 8190kWh), or 77.6300 less than the 0.21/kWh cost of lead-acid batteries. The investment’s payback period has been minimized from 6.2 years to 3.8 years. Third-party laboratory tests prove that one model of 2560Wh battery is still holding 72% capacity (1843Wh) after 12 years’ use under an 80% DoD and one cycle per day with a residual value rate of 35% (134.4) of the initial cost, several times greater than the 515 of lead-acid batteries.
Under the dynamic load condition, the instantaneous energy release is determined by the 2560Wh LiFePO4 battery’s maximum output capacity. Its continuous discharge power reaches 5kW (2C rate), and the pulse power (30 seconds) reaches 8kW, and that is sufficient to power three 1.5P air conditioners (each with 1.3kW of power consumption) to operate simultaneously. In the 2022 California wildfire emergency power supply case, this definition of battery continuously supplied 45 hours of medical equipment load value of 2.8kW, actually providing 126kWh of energy (4.9 times rated value), achieving over-limit utilization with deep cycling (DoD 95%) and tiered charging strategies. But this accelerates capacity weakening to 82% of target cycle life value.