The special charger requirement is overhyped and designed to sell their chargers. Yeah, if you run it really dead you might have to put another batt in parallel for while, but likely you will not. They do like a little higher float voltage after the batt is charged (and it goes into trickle mode) but my Tender Jr seems to do just fine and my cars alternator puts out over 14 volts. If your car puts out 13.5 or less you might have an issue. Most alternators and VRs put out more than that.
