Batteries in storage will lose up to 50% of their charge in just 12 days! Standard trickle chargers can overcharge and permanently damage the battery. The Battery Tender puts an end to this worry. Connect the alligator clips to your battery terminals, plug it into a wall outlet, and that's it! It will maintain a 100% charge constantly: enough to ensure starting power, but not enough to boil away electrolyte and damage the plates. It even senses incorrect connections and will not charge if the polarity has been reversed. Output is 1.25 amps. Limited 10 year manufacturer's warranty.