40 Amp Engine Start: helps get the charging process started quickly 15 Amp Rapid Charge restores energy via a continuel electrical current 3 Amp Maintainer keeps the battery at optimal level by charging as needed Alternator Check to indicate potential alternator issues Battery reconditioner determines viability of battery to accept a charge. If battery is not in optimal condition it automatically switches the battery reconditioner function on to reverse sulfate build-up on battery plates to improve charging carrying capability and extend battery life.