So far it seems as if there are a few converters that do an adequate job--but none that do a FANTASTIC job without modification.
Even premium chargers such as the charging circuit in Magnum inverter/chargers don't necessarily work perfectly. I had to limit the input amperage to the charger to prevent it from overloading past the 125 amps it can produce when my 'new to me' surplus acid agm batteries were "hungry".
I think a nearly perfect charging device may need to use the technology from the smartgauge to constantly monitor state of charge (it does that 1500 times a second) and then control the charging parameters.