In off-grid energy storage usage, lifepo4 battery (lithium iron phosphate battery) cycle life is 6 to 10 times longer than that of lead-acid batteries. The U.S. Department of Energy, in a 2023 report, stated that under 80% deep discharge (DOD) conditions, lifepo4 batteries can withstand 3,000 charge and discharge cycles with a capacity retention rate of ≥80%, while lead-acid batteries can withstand only 500 cycles (capacity attenuation to 50%). Consider one such off-grid photovoltaic project in Africa for instance. Upon converting to lifepo4 battery, the system replacement frequency rose from 2 years to 10 years, the life cycle cost reduced by 62%, and the operation and maintenance cost reduced by 2,400 US dollars per kilowatt-hour per year.
With regard to energy density, the 125Wh/kg of lifepo4 battery has a much wider gap than the 35Wh/kg of lead-acid battery. This has reduced the off-grid version of Tesla Powerwall by 68% in terms of volume. With the same 20kWh energy storage requirement, installation space has been reduced from 4.2 cubic meters to 1.3 cubic meters. The ultra-low temperature adaptability comparison is more significant: Under a low-temperature scenario of -20°C, lifepo4 battery can still discharge 85% of the rated capacity, whereas the output of lead-acid batteries decreases significantly to 45%. Whereas at 60°C, the rate of attenuation in capacity for the latter is a mere 0.5% annually, but the former’s is as much as 12% annually.
The economic cost benefit analysis indicates that the 10-year lifecycle cost of ownership of lifepo4 battery is $0.18 /Wh, being 51% less than the case with lead-acid batteries at $0.37 /Wh. In 2024, Germany’s Fraunhofer Institute found that lifepo4 battery-powered off-grid systems cut the payback time to 4.3 years (7.1 years for the lead-acid option) and the internal rate of return to 14.7% (8.2% for lead-acid). This is because its discharge and charge rate reaches as much as 98%, while for lead-acid batteries it is at best 75% to 85%. This means that using the same sunlight, it can store an additional 820kWh of electricity annually (based on a 5kW system).
In the environment, the lead emissions of lifepo4 battery are zero, and the cobalt content is 100% lower than ternary lithium batteries. The United Nations Environment Programme states that lead-acid batteries produce 230,000 tons of lead contamination all over the world per year, and the treatment cost is 28% of the selling price. The recovery rate of lifepo4 battery reaches as high as 96% (EU Battery Regulations data in 2023), and the thermal runaway temperature is as high as 270°C, 3.5 times the 60°C safe temperature of lead-acid batteries. The 2022 Australian bushfire disaster area case suggests that the lifepo4 battery off-grid system has minimized the probability of fire to 0.003 times per thousand sets, a much lower level than 0.12 times per thousand sets of the lead-acid solution.
In terms of load response performance, lifepo4 battery peak power density is as much as 3000W/kg, five times that of lead-acid batteries. This enables it to experience only a 2.7% drop in voltage under sudden load conditions (such as powering a 3kW water pump), compared to a precipitous 15% drop for lead-acid batteries. In the off-grid microgrid utilized by the typhoon-stricken areas in the Philippines, the lifepo4 battery system readily achieved an availability rate of 98.6% in delivering power, a 41 percentage point improvement over the original lead-acid setup. Market data confirm the trend towards change: Bloomberg New Energy Finance figures show that lifepo4 batteries accounted for 73% of new off-grid energy storage installations globally in 2023, and this will rise to 92% by 2030, finally putting an end to the domination of lead-acid batteries.