Given that your AC requires 900 watts to run and the invertor would have about 100 watts loss while running you would need an alternator capable of providing 1000 watts (84 ampps at 12 volts) just to keep the AC operating. To operate from batteries for more than a few minutes you would need a battery bank weighing more than the vehicle. And this is without running any other accesories in the vehicle or operating the vehicle itself!
