ORGANIC EXPANDER FOR LEAD STORAGE BATTERY

An organic expander for a lead storage battery, the organic expander containing lignin in which the methoxy group content relative to the solid content is 3 to 20 mass %, wherein the organic expander contains an organic acid in an amount of 0.0001 to 5 mass % relative to the solid content of the organic expander. It is possible to improve charge acceptance while maintaining the discharge characteristics of the lead storage battery.