Would you like to have an extra battery on hand for your Ebike? This is the main battery that fits into the frame rail of several Eunorau models. Many Ebike riders choose to keep an extra battery and charger at their office or vacation home -or- carry an extra fully charged battery when they are going for an extended ride far from home. Keep riding all day long with an extra battery for your Ebike. You can also choose to bundle the battery with an extra charger as well.