The charging time of LiFePO4 batteries (lithium iron phosphate batteries) is influenced by several factors: charging current, capacity of the battery, ambient temperature, and the efficiency of the charger. As an example, consider a lifepo4 battery with a 100Ah capacity. At the normal charging current of 0.5C (that is, 50A), the time needed to charge from 20% SOC to 100% is approximately 1.6 hours, which is theoretically calculated as (100Ah×80%) /50A=1.6 hours. But in practical applications, the final constant voltage stage of the charging will extend the entire time, usually by 10%-15%, so the actual time will be approximately 1.8-2 hours. If 1C high-rate charging (100A) is used, it can be as brief as less than 1 hour, but it needs to be designed with a high-power supportable BMS, e.g., BYD’s blade battery solution can increase charging peak power to 120kW, but restrict the increase in temperature within 5 ° C.
Temperature is crucial to the efficiency of charging. Experimental results show that under the best condition of 25℃, charging efficiency of lifepo4 battery can reach 98%, while at low temperature -10℃, charging time is delayed by more than 30%, and risk of capacity reduction is increased by 5%-8%. Tesla Powerwall energy storage product uses active temperature control technology to maintain the battery temperature within the range of 15-35 ° C by utilizing a heat film so that the charging rate remains constant at 4 hours (20% to 100%). In addition, the conversion efficiency of the charger is also necessary: in charging a 300Ah battery pack with a 30A charger with 95% efficiency compared to one that has 90% efficiency, the energy lost is 15% less, which amounts to an annual savings of approximately 200 yuan (assuming a price of 0.6 yuan /kWh).
Under working conditions, lifepo4 battery charging regulation should be able to satisfy certain demands. For example, Ningde Times’ battery pack for electric buses supports 2C fast charging, which can charge 80% of capacity (from 200kWh to 360kWh) within 30 minutes, meeting the daily operating needs of 300 kilometers of bus routes. The home energy storage system generally uses 0.2C slow charging to extend the cycle life, such as Huawei’s home green power solution in 5kW photovoltaic input, 10kWh battery pack is charged within 2 hours, with time-of-use tariff strategy can save 40% on the cost of energy. According to the “2023 Global Energy Storage Technology White Paper” data, lifepo4 battery capacity retention rate is more than 80% after 2000 cycles, better than 60%-70% of terpolymer lithium batteries, which reduces its whole life cycle cost by more than 25%.
The technological breakthrough of fast charging also enhances the balance between time and safety. In 2022, Guoxuan Gaoke’s “Qichen” battery supports 4C charging, and is able to increase 400km in 10 minutes (based on 60kWh battery pack), the key of which is to increase the rate of lithium ion diffusion by 50% with porous electrode structure, and reduce the possibility of thermal runaway to 0.001%. Market data show that commercial models equipped with the technology have achieved a one day’s high-frequency transportation of 1,200 kilometers in the logistics sector, the frequency of recharging has been reduced from 3 a day to 1, and the working efficiency has increased by 35%. Besides, the charging infrastructure also needs to be upgraded: Ningde Era EVOGO converter station can recharge the battery in 1 minute, and the single lifepo4 battery module battery density is as high as 160Wh/kg, 12% higher than the last generation.
From an economic perspective, the charging cost advantage of lifepo4 battery is enormous. For instance, in 48V 200Ah communication base station backup power system, the price of one full is only 6.4 yuan (0.8 yuan/kWh electricity unit price), compared with lead-acid battery 10.2 yuan by 37% savings and from 500 to 4000 times cycle life extension, 60% reduction in annual maintenance. According to the Bloomberg New Energy Finance report, in 2023, the global lifepo4 battery production capacity exceeded 800GWh, and the scale effect lowered the price to $90 /kWh, 40% lower than that of 2020, further speeding up its application in energy storage, electric vehicles and other fields, and it is estimated that the global market share will reach 65% in 2030.