While I agree that a proper converter for lithium does not yet exist, my solar controller does a fairly good job. I'm using a Victron 100/30 with 320 or 480 watts (depending on whether I add a portable panel) feeding a pair of Battleborn batteries.
While it required using the app to choose the correct settings, the Victron supplies 14.4V until the batteries are full, switching to absorption at around 98%. Absorption lasts 1 hour (30 minutes per battery as suggested by Battleborn to allow cell balancing), then switches to float set at 13.6V.
If a solar controller can do this, why can't a converter?