A method for operating a lead acid storage battery charged by a natural energy power generation device and discharged to an external circuit, the lead acid storage battery being connected to the power generation device in order to compensate for fluctuations in the amount of power generated by the power generation device, where in said method for operating a lead acid storage battery including: maintaining of a state of charge of the lead acid storage battery in a range of 30 to 90% by stopping a discharge of the lead acid battery when the state of charge becomes less than 30% and stopping a charge of the lead acid battery when the state of charge exceeds 90%, where a fully charged state of the lead acid storage battery is 100%; and charging and discharging the lead acid storage battery while keeping the battery voltage in a specified range of 1.80 to 2.42 V per cell when 25°C is taken as a reference temperature and an ambient temperature of the lead acid storage battery is the reference temperature; charging and discharging the lead acid storage battery when the ambient temperature has risen above the reference temperature by carrying out a correction for reducing an upper limit value and a lower limit value of the specified range by a correction amount selected in a range of 4 mV/°C to 6 mV/°C per cell in accordance with an amount by which the ambient temperature has increased over the reference temperature, whereby a corrected voltage range is obtained; and keeping the battery voltage in the corrected voltage range; and charging and discharging the lead acid storage battery when the ambient temperature has fallen below the reference temperature by carrying out a correction for increasing the upper limit value and the lower limit value of the specified range by a correction amount selected in a range of 4 mV/°C to 6 mV/°C per cell in accordance with an amount by which the ambient reference temperature has decreased from the reference temperature, whereby a corrected voltage range is obtained; and keeping the battery voltage in the corrected voltage range wherein the maximum discharge current of the lead acid storage battery during operation is kept at 0.4 CA or less where C is the rated capacity [Ah] of the lead acid storage battery, the maximum charge current of the lead acid storage battery during operation is kept at 0.3 CA or less where C is the rated capacity [Ah] of the lead acid storage battery. maintaining of a state of charge of the lead acid storage battery in a range of 30 to 90% by stopping a discharge of the lead acid battery when the state of charge becomes less than 30% and stopping a charge of the lead acid battery when the state of charge exceeds 90%, where a fully charged state of the lead acid storage battery is 100%; and charging and discharging the lead acid storage battery while keeping the battery voltage in a specified range of 1.80 to 2.42 V per cell when 25°C is taken as a reference temperature and an ambient temperature of the lead acid storage battery is the reference temperature; charging and discharging the lead acid storage battery when the ambient temperature has risen above the reference temperature by carrying out a correction for reducing an upper limit value and a lower limit value of the specified range by a correction amount selected in a range of 4 mV/°C to 6 mV/°C per cell in accordance with an amount by which the ambient temperature has increased over the reference temperature, whereby a corrected voltage range is obtained; and keeping the battery voltage in the corrected voltage range; and charging and discharging the lead acid storage battery when the ambient temperature has fallen below the reference temperature by carrying out a correction for increasing the upper limit value and the lower limit value of the specified range by a correction amount selected in a range of 4 mV/°C to 6 mV/°C per cell in accordance with an amount by which the ambient reference temperature has decreased from the reference temperature, whereby a corrected voltage range is obtained; and keeping the battery voltage in the corrected voltage range wherein the maximum discharge current of the lead acid storage battery during operation is kept at 0.4 CA or less where C is the rated capacity [Ah] of the lead acid storage battery, the maximum charge current of the lead acid storage battery during operation is kept at 0.3 CA or less where C is the rated capacity [Ah] of the lead acid storage battery.