Over at Solar Guppy's board, user IBOC has been looking at a SkyStream Wind Turbine system. And through SkyStream's documentation and discussions with the vendor, it turns out that they use their grid tie wind turbine to back drive standard off grid 120/240 VAC inverters (like Outback and Xantrex) and charge battery banks. Skystream uses a small battery monitor to control the wind turbine to turn off its grid tie feed once the battery bank is charged.

Also, IBOC has been looking at the Xantrex documentation for the new XW series and it too appears to use this back feed charging of a battery bank with feed back to the grid tied inverter to control battery state of charge.

Here is the link to the SG thread, and IBOC's last post:

Well, the reason the skystream works is because it has its own voltage sensor for the batteries that you buy separate. When the batteries reach full charge, the windmill receives signal to power down and put on the brakes. Thats why the skystream system works.

When researching this concept I found 2 other things that may interest you guys.
#1) the Sunny Island system works exactly like this through AC Coupling, in essence allowing you to use Grid Tied 600v inverters instead of 120v charge controllers. The sunny island ties in directly to SunnyBoy WindyBoy grid tie inverters using them as charge controllers when the grid is not functioning.
#2) I also found an AC Coupling diagram for Xantrex XW inverters that showed a feature I was not able to find any info on. Apparently you can take a Xantrex GT inverter, connect it to an XW Inverter on the AC out side. And connect the two together with a communication cable allowing the XW system to shut down the GT in the event that the Batteries reach a full state of charge.

Both concepts are probably worth further investigation. It would seem to me that this method of setting up a solar power system, grid tied with backup, is likely much simpler than using charge controllers and would effectively eliminate charge controllers from the setup. Even though, apparently, you can still use them if you want to. Also I think I can use this setup to have a negative ground battery based backup connected to a positive ground solar array and not lose any efficiency in panels manufactured like my "Sunpower" solar panels.
Sounds like a great way for those of us with Grid Tie system to add battery backed off grid systems that can still use the grid tie solar array without rewiring/adding a DC charge controller (bypassing the old problem of high voltage DC grid tie inverter inputs vs the low voltage inputs that DC charge controllers require).

-Bill