You'd need to build a high voltage battery as the turn on voltage of the inverter is 120V so we are in lethal DC land. Also the impedance of the supply of a battery is significantly lower than that a solar string so you risk damaging the inverter. The inverter is expecting the voltage to drop rapidly as current flows but it wont from a battery.
Saying that I have personally done something similar in the past to transfer grid power to an OffGrid system. I used several grid powered PSUs in series to get the DC voltage up to about 130V and connected it to a standard SMA grid tie inverter with a power limit output set on the inverter to stop the power supplies overloading.
Thankfully those days of craziness are over for me, I would not recommend what you are thinking. You could sell on your Solis and replace it with a hybrid model which takes batteries. Then you need to work out how to get the inverter and the powerall to play nicely.
Don't do this at home folks, especially if you don't like bangs and magic smoke.
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