In cycle life, lifepo4 (lithium iron phosphate battery) charge and discharge cycles can be 2,000 to 5,000 times (DOD 80%), but the lead-acid battery is just 300 to 500 times (DOD 50%). The former’s life is prolonged 4 to 10 times. Let’s take Tesla Powerwall as an example. Its lifepo4 battery cells proved in the UL 1973 certification test that the capacity retention rate still reached 80% after 4,000 cycles. By comparison, the capacity of AGM lead-acid batteries of the same capacity (e.g., Victron Energy 12V 200Ah) decays to 50% after 1200 cycles. According to data from the National Renewable Energy Laboratory (NREL) of the United States, the calendar life of lifepo4 is 8 to 15 years (with an average annual capacity decline rate of 1.5%), which is much higher than the 3 to 5 years (with an average annual capacity decline rate of 6% to 8%) of lead-acid batteries.
As to cost-effectiveness, although lifepo4’s initial investment is 2 to 3 times that of lead-acid batteries (e.g., 12V 100Ah, the former is about 600 US dollars and the latter is about 200 US dollars), its single-cycle cost is only 0.15 yuan /Wh, far lower than 0.8 yuan /Wh of lead-acid batteries. Off-grid photovoltaic systems, for example. Lead-acid batteries need to be replaced 3 to 5 times in a 10-year period, which costs a total of over 3,000 US dollars. Lifepo4, however, needs just a one-time investment and lowers the maintenance expenses by 67%. The 2023 German Enercon Company study report indicates that in the scenario of an average daily discharge depth of 60%, the overall life cycle return rate (IRR) of lifepo4 batteries is 14.7 percentage points higher than that of lead-acid batteries.
In the environmental adaptability aspect, lifepo4 still has 70% of its capacity discharging in the low temperature of -20°C (at which lead-acid batteries can only discharge 35%), and its high-temperature resistance can reach 60°C (lead-acid batteries’ life will be cut down by 50% when the temperature is over 45°C). BYD’s Blade Battery test data shows that in the Sahara Desert region (daily average temperature 45°C), lifepo4 energy storage system capacity attenuated by 9.2% after three years of operation, while the gel lead-acid batteries employed in the same period have died and been abandoned. In addition, the Coulombic efficiency of lifepo4 (98%-99%) is far better than that of lead-acid batteries at 80%-85%, which implies that energy loss can be reduced by 12% in photovoltaic off-grid systems.
The maintenance requirements are rather disparate. Lead-acid batteries need frequent replenishment (with 0.5L/kWh distilled water consumed every quarter) and sulfate crystallization control, while the hermetically sealed design of lifepo4 enables zero maintenance. After the replacement of lead-acid batteries with lifepo4 forklift batteries in Amazon’s logistics center in 2022, the average annual maintenance time per unit was reduced from 38 hours to 2 hours, and 94% of labor costs were saved. In safety indicators, lifepo4’s thermal runaway initiation temperature is as high as 270°C (while that of lead-acid batteries is only 160°C), and the needle-puncture test peak temperature is maintained within 80°C (up to 400°C for lead-acid batteries), reducing the fire risk by 89%.
In terms of charging and discharging performance, lifepo4 is capable of 2C rapid charging (30 minutes to 80%), which is 10 times the 0.2C charging rate of lead-acid batteries. Northvolt’s demonstration project in Sweden shows that an electric yacht charging system based on lifepo4 can complete a 200kWh energy replenishment in one hour, while the lead-acid solution takes eight hours, meaning 700% better operational efficiency. In energy density, lifepo4’s 120-160Wh/kg is three times the 30-50Wh/kg of lead-acid batteries. When the Tesla Semi truck’s range is more than 800 kilometers, the battery pack’s weight is actually 2.3 tons lighter than the lead-acid solution.