As batteries age, some bulging of the side and end walls caused by growth of internal components is normal. Due to the weight of electrolyte, some case bulging is normal with new batteries. Excessive bulging may be the result of operation at higher than recommended temperatures (>120ºF or 49ºC) or from prolonged undercharge causing excessive sulfation. This can cause permanent loss of capacity and shorten battery life. Severe bulging may be an indication that the batteries have been frozen. Freezing can do permanent damage to the internal components in batteries and could result in an exploded battery. Batteries that are frozen or have been frozen should not be used.