No, I'm not confused. converting AC to Dc is what they do in a grid-tie system. They're also partially responsible for cutting power in the event of a power failure so as not to backfeed the power grid and kill a lineman. In a system that also utilizes batteries these will be part of the system used to charge the batteries, except that when you buy grid-tie this isn't part of the package. If you bother to read some of the press materials about these batteries you will find mention of some hardware manufacturers and mention of "hybrid" inverters. That will be the gear needed to properly charge the lithium battery pack and to properly feed the home from the battery pack when the time is right or power is lost but NOT backfeed the grid one would hope. See here -> http://www.teslamotors.com/pre... and for ease try searching for Fronius to get an explanation.
There ARE some inverters now that will do this - with lead-acid batteries. I'm betting you will find that these don't use the same charging curve as lithium, if you've ever charged li-po packs for RC use you'll know why (lol). A firmware update might allow these to work and you'll primarily find these used for off-grid homes. Grid-tie seldom have battery packs because the cost nearly doubles and lead-acid batteries must be properly maintained which is a PITA. Oh and lead-acid are often replaced every 5-7 years or so depending upon how many times you've drawn them down too far or too fast and damaged them YMMV.
So yeah, I'm familiar with inverters and what the issues here are. What did you think you could just hook this up like a solar panel and it would charge and discharge properly? I think perhaps I'm not the one who's confused here...