Batteries in storage will lose their charge, up to 50% in just 12 days. Batteries left uncharged through the winter can freeze, causing the casing to crack. Connect the alligator clips to your battery terminals, plug it into a wall outlet. It will maintain a 100% charge constantly. It even senses incorrect connections and will not charge if the polarity is reversed. Includes terminal connectors for motorcycles too! Limited 10 yr manufacturer's warranty.