Does anyone know if you can connect one of these to the grid without the batteries? Then add them later?
thanx

No,

The GTFX inverters can not be directly connected to solar panels, they require a charge controller. The Charge controllers as well as the inverter to some extent require batteries.

A cheap/small battery bank will work ( 100ah Wal-Mart Deep Cycle ) can be had for about $250.00 , and give you about 2kWh of backup, this will work OK for smaller installations ( PV ), I have run this way for about 3 years.

If you’re going to run the inverter at full load, gridtie or not you'll need a bigger battery bank, rule of thumb is 100ah battery rating per 1Kw of inverter load or the AC ripple will overwhelm the charge controller/inverters

Also, cheap Lead Acid is high in tar losses, your looking at about 60-70% efficiency power in/power out. The GTFX also, as just a gridtie inverter is at the very bottom off efficiency, about 91% ... and in the charger control losses and battery tar losses and you will be in the low 80% range, compared to current gridtie only units in the 95% range