When selecting wall mounted battery storage for photovoltaic panels, the battery capacity should be comprehensively determined according to the power generation performance of photovoltaic panels, the power consumption of loads, the minimum overcast interval, and the duration of continuous power supply for loads according to the actual situation. For example, the existing 1000 watt photovoltaic panel, the daily power consumption of the load is 1 kilowatt hour, the annual average minimum overcast interval is 3 days, and the wall monuted battery 10kwh system should be guaranteed to supply power to the load for 5 consecutive days. The analysis process is as follows: 1000 watt photovoltaic panels generate 1 kilowatt hour of electricity theoretically. Considering heat transmission and other losses, the actual hourly power generation may be 0.8 kilowatt hour. Assuming that the actual full load power generation time of a day is 4 hours, the photovoltaic panels can generate 3.2 kilowatt hour of electricity a day. The load consumes 1 kilowatt hour of electricity every day, so the remaining electricity every day is 2.2 kilowatt hours. If the battery is required to ensure stable power supply for the load in 5 consecutive rainy days, and the power loss of the battery is 0.2, the battery should be able to store at least 6.25 kilowatt hours of electricity. According to the actual remaining electricity of 2.2 kilowatt hours per day, the battery can be fully charged within 3 days before the next rainy day. Therefore, under this working condition, it can be considered that the storage capacity of the optional battery is not less than 6.25 degrees