Some misconceptions here.
Yes I did/do use large grid tie inverters to charge the battery bank... it is only 800ah@48v or about 39kwh in size.
However, I have had over 4kw from the grid ties charging the batteries, and running the house at the same time.
First you need a decent pure sine wave inverter/charger.
Only the SMA island one works in the commercial world as far as I know.
I built a 8000w pure sine wave unit for less than $400, and included 18uh choke in the drive arm of the torroid transformer I made.
This choke is the key somehow. I had started out to kill off the 20khz switching signal out of the iron cores way, but instead found that a tiny choke made the idle come down to 25 watts or so. It seems to help the fets to switch on fully, before the current starts to flow, as it does two things..... lowers the idle current from 200 watts to only about 25 watts...... and the other benefit, is you can hook up as many kilowatts of grid tie as you please, and the transfomer and fets run very cool.
The grid tie units are not tampered with in any way, and will switch out from + - half a hertz, and any voltage variations within the AS3777 ( I think.. code).... very strict.
So it is the inverter that is critical in it's design.
Mine looks like this.
The box is from a gutted grid tie unit, and the transformer is made up from 2 torroids out of 3kw grid ties.
................oztules