DieHard Platinum 6V/12V Battery Charger and Maintainer for $21.59 shipped.  Here is a screenshot for your reference.  It features 3 Amp charge, scrolling digital messaging, 5 stage charging process, float-mode monitoring, digital scrolling messaging, and versatile quick-connect harness with three connector options: 50-amp clamps, 12V accessory plug, or permanently attachable ring connectors.