In off-grid photovoltaic scenarios such as remote mountainous areas, pastoral areas and islands without grid coverage, 2V lead-acid batteries are the first choice for energy storage due to their excellent adaptability. Off-grid photovoltaic systems require day-night charge and discharge to cope with light fluctuations. 2V deep-cycle lead-acid batteries can withstand frequent charge and discharge, with a cycle life of more than 800 times under 80% deep discharge, fully adapting to the intermittent power generation characteristics of photovoltaics. The battery modules can be expanded on demand, and multiple groups of series and parallel connections can build a large-capacity energy storage system to store surplus photovoltaic power in the day and ensure continuous power supply at night and on rainy days. Its maintenance-free design greatly reduces operation and maintenance costs in remote areas.