I recently purchased 9 255W solar panels, rated 30V, 8.4 A, and a SMA 7.0 grid tie inverter. Looking to use in an off-grid application, but the inverter output is 240Vac it appears. Will I be able to use this with a battery bank ?
Grid tie inverters require that they see the grid on their AC side before they'll start outputting power. Usually they will want to see a low impedance power source there too. They do this by trying to tug the voltage around and seeing how much current it takes to do it. If they find the current required is very low they'll consider the grid to have failed and shut down the inverter.
Some inverters have hidden service menu configuration items that will let them work standalone. Some can be fooled into thinking the grid is present by connecting a low power standalone inverter to their output. I don't recommend either of these approaches.
If you need to operate stand alone IMO you need to get an inverter that is intended to operate that way. The MPP all-in-one inverter/charger/solar controllers are popular with people on this forum, so that might be a place to start your voyage.
Yes, if fit has "Secure Power", you can get 120V 2000W max while the sun shines.
What you really want to do is get one Sunny Island plus a 120/240V transformer, or two Sunny Island, for 120/240V split phase.
Those and Sunny Island were made for each other. I have four Sunny Island installed (my picture) and Sunny Boy inverters coming out of my ears.
It is primarily for lead-acid batteries. Lithium are available, but only select model BMS, expensive, talking the right serial communication language.
2500W of PV - off to a good start, but if you set up two Sunny Islands you can support 10x that much.