MTD 791-182391B  Battery, 12 Volt

The most common types of Battery used in outdoor power equipment are acid-based batteries primarily used to support electric starter systems. Electric starter batteries are normally sold "dry" (meaning without battery acid) so that they may be safely shipped to the end customer. Before installation, a dry battery must be filled with acid, usually at a local automotive store. Note the position of the positive and negative terminals before you remove the old battery as that can differ on some equipment.