Lifeline batteries. Auto or truck. Underhood. 13.8 -14.1 volts CONTINUOSLY for 10-years and at underhood temperatures. Concorde wants their batteries to last 15- years to make them look even better. There is no converter in the fricken world that will float the Lifeline or any other AGM at theoretical perfect voltage when ambient temperarures exceed 80F. Or less than 50F. 13.6 is FINE until temps exceed 100F. Do a float amperage test somtime on a Lifeline and see the amperage difference between 13.4 and 13.6 volts. SURPRISE!