Off-grid photovoltaic systems cannot connect to public power grids, making backup energy storage the core of stable operation. lead-acid batteries dominate this field due to excellent adaptability. They operate through reversible electrochemical reactions: storing excess power converted by photovoltaic modules in daytime and releasing electricity to power loads when sunlight is insufficient. Deep-cycle lead-acid batteries adapt to frequent charge-discharge cycles of PV systems and resist daily working condition fluctuations. With strong instantaneous power supply capacity, they quickly fill power gaps and ensure continuous power supply for remote residences, outdoor base stations and other off-grid photovoltaic scenarios.