After the expansion of the solar power system, some sets of lifepo4 batteries must be parallel to ensure voltage stability (±0.05V) and capacity fluctuation < 5%, and dynamic balance through smart BMS (Battery Management System). For instance, in the 48V system, when four 12V 200Ah lifepo4 batteries are paralleled, the capacity is 800Ah, and the continuous discharge power can be 24kW (0.5C), which is 300% higher than that of a single-battery system. A field test of a German domestic photovoltaic scheme demonstrates that by increasing the number of lifepo4 cells (each 5kWh) to 3 sets, night time power supply hours were increased from 8 to 24, the rate of photovoltaic consumption was increased from 68% to 92%, and the annual electricity bill was saved by €1,240 (on calculation at €0.35/kWh).
In terms of cost-effectiveness, for every additional 1kWh of lifepo4 capacity for energy storage (approximately 150), the self-sufficiency rate of the system can be increased by 123,000, but grid-purchased electricity will decrease by 83% (from 4,200kWh/year to 714kWh), and the payback period on return on investment will decrease from 6 years to 3.8 years. Byd’s modular blade battery is crafted to facilitate plug-and-play abilities. Only 15 minutes is needed for installation of every 5.12kWh cell, decreasing operational and maintenance costs by 62%.
It relies on advanced management technology. Huawei’s FusionSolar solution employs AI algorithms to achieve maximum real-time charging and discharging strategies. The SOC (State of Charge) sync error of parallel-connected lifepo4 batteries is ≤±1%, whereas ±8% for lead-acid batteries is considerably worse. Tesla Powerwall’s stacking design can have up to 10 groups in parallel (a total capacity of 135kWh), with a charging rate of 7kW per group. The filling rate of the energy storage in the photovoltaic system’s midday peak has risen from 75% to 98%. A 2023 off-grid clinic project in South Africa showed that 16 lifepo4 batteries with a total capacity of 128kWh were connected wirelessly in parallel configuration, achieving the power supply stability of 99.99% for medical appliances (voltage fluctuation < ±1%).
Safety regulations dictate that the difference control of temperatures among several battery groups (≤±2℃) and response time of the short-circuit protection should be less than 20ms. UL 1973 certification demands that parallel lifepo4 battery packs be subjected to the 200% overload test, and the fusing action time should be less than 5ms (50ms for lead-acid systems). In a Marine PV system installed in Bergen, Norway, six groups of lifepo4 cells (each group 24V 400Ah) brought the charging efficiency from 45% to 82% through self-heating coordination (total power usage < 100W) under the -25℃ operating environment, and cycle life standard deviation was maximized to ±2.1% (±12% without temperature control).
Field test has validated the extended value. A particular off-grid school in East Africa has installed 20 sets of lifepo4 batteries (total capacity 200 KWH), and a 25kW photovoltaic array, and increased the average daily power supply from 180kWh to 520kWh and reduced the daily usage time of the diesel generator from 10 hours to 0.5 hours. Its smart BMS active balancing current is up to 5A, and the median capacity attenuation rate is as low as 0.007%/cycle (passive balancing is 0.02%/cycle). The new 2024 regulations in California require the development of energy storage systems to be to a carbon footprint of less than 50kg CO₂/kWh. However, the 28kg weight figure of lifepo4 becomes the first choice compliance solution, with its year-on-year market share increasing by 37%.
