A car battery cover is not a necessity for any battery, but they are a nice thing to have. They cover the top of the battery, which helps prevent corrosion from developing on the battery terminals. A sealed battery simply means that the battery acid cells are sealed, and they cannot be accessed. These batteries are basically maintenance free but at times they do need to be changed. They can be charged or jump started like a regular battery, so keeping the terminal posts clean and corrosion free is important. A battery cover can help keep the posts clean. These covers normally snap on and are fairly inexpensive.