LiFePO4 (lithium iron phosphate) batteries are due to their unique chemical composition and material characteristics responsible for their outstanding deep cycling capability. Experimental data show that LiFePO4 batteries are able to cycle 2,000 to 5,000 times stably (capacity retention rate > 80%) in 100% deep discharge (DoD) mode, far exceeding that of lead-acid batteries (300 to 500 times, capacity attenuation to 50%) and ternary lithium batteries (800 to 1,500 times). For instance, BYD’s real test in 2023 demonstrated that its commercial vehicle power battery pack (LiFePO4 system) maintained a capacity of 87% after six years operation at an average daily DoD of 90%, and its cumulative life cycle energy throughput exceeded 12MWh (lead-acid batteries only 1.8MWh). NREL (USA National Renewable Energy Laboratory) research indicates that LiFePO4 has an olidine crystal structure which, when subjected to lithium-ion intercalation/deintercalation, undergoes only a 6.8% volume change, as opposed to 20% in the case of lithium cobalt oxide, and the lattice stress is reduced by 72%, effectively precluding electrode pulverization.
High charge and discharge efficiency and minimal internal friction characteristics further contribute to the advantages offered by deep cycling. The charging and discharging efficiency of LiFePO4 batteries is 95%-98% at the 1C rate (80%-85% for lead-acid batteries), and the internal resistance growth rate is less than 0.05mΩ per cycle (0.3mΩ per cycle for lead-acid batteries). Results of one specific South African off-grid solar installation in 2022 show that the LiFePO4 battery-based energy storage system experienced only 4.3% annual loss of energy (21% for lead-acid battery systems) under regimes of two deep cycles per day, corresponding to an additional annual revenue of $12,000 per megawatt-hour (at a photovoltaic electricity price of $0.15 per kWh). TUV Rheinland Germany tests prove that its discharge voltage platform fluctuation range is ±0.05V (±0.2V for lead-acid batteries) and its energy release linearity R² in the 80% range of DoD is 0.999, which keeps its inverter conversion efficiency stable at over 97% (89% for the lead-acid solution).
Temperature flexibility broadens application areas of deep cycling. LiFePO4 batteries can still provide 80% capacity even at a low temperature of -20℃ (compared to lead-acid batteries, whose capacity is only 45%), and their high-temperature cycle life at 45℃ is 8 times higher than lead-acid batteries (2000 times compared to 250 times). The example of the 2021 Antarctic research station proves that a LiFePO4 battery-powered unmanned weather station operated at an average daily Depth of Discharge (DoD) of 95% and operated continuously for 18 months in -40℃ conditions (the rate of capacity degradation was only 0.8% per month, compared to nickel-metal-hydride battery packs degrading at 3.5% per month over the same period). China Shipbuilding Industry Corporation’s 2023 report proved that the LiFePO4 battery pack in deep-sea robots had successfully undertaken a 5,000-meter diving task in seawater at 5℃ (10MPa pressure). Capacity retention was 91.3% and internal resistance increase was below 5% after 300 deep cycles (the capacity of lithium titanate batteries reduced by 19% under identical conditions).
Cost-benefit reconstruction of the deep circular economy model. Whereas the initial cost of lifepo4 batteries is about $0.15 /Wh (lead-acid batteries are $0.1 /Wh), their lifecycle cost is only $0.0003 /Wh per cycle ($0.001 for lead-acid batteries). A LiFePO4 battery-based 10MW/40MWh energy storage system in a California microgrid has concluded that it performed a total of 12,000 charge and discharge cycles (90% depth of discharge, DoD) in 15 years, and the cost per kilowatt-hour is currently $0.02 ($0.08 for the lead-acid solution). Bloomberg New Energy Finance statistics show that in the 2023 global energy storage auction, LiFePO4 batteries won at a rate of 78% and their deep cycle tolerance enhanced the project IRR by an average of 2.3 percentage points (9.1% to 11.4%).
The reliability of the technology is validated through practical application. Tesla Megapack energy storage system (LiFePO4 system) has operated 1.5 deep cycles per day at Hornsdale power station in Australia. The capacity retention ratio reached 94.6% after four years of operation, and the annual decline rate was only 0.14% (ternary lithium solution’s annual decline rate is 0.8%). In 2024, CATL introduced the third-generation CTP technology, which increased the energy density of the LiFePO4 battery system to 180Wh/kg (22% improvement compared with the second generation), and enabled a deeper discharge level of 30% (DoD improved from 80% to 95%) at constant volume. In NASA’s theoretical model of a lunar base, the LiFePO4 battery was employed as the main energy storage component because it was able to maintain 10,000 deep cycles (loss of capacity < 5%) in a vacuum radiation environment (the equivalent of 200 times Earth’s surface level radiation), which became the standard of energy dependability in harsh conditions.