ORGANIC EXPANDER FOR LEAD STORAGE BATTERY

Provided is an organic expander for a lead storage battery, said organic expander containing lignin in which the methoxy group content relative to the solid content is 3 to 20 mass%, wherein said 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.