The doors that have no mechanism or track inside the garage are usually the type where the top of the door stops moving inwards on the last part of travel, when the bottom of the door is moving upwards. Those are difficult to automate because pulling on the top of the door won't finish the operation.
https://www.accessgaragedoors.com/mechanism/In our previous house we had two doors like that, and there are things called canopy adaptors, which we used, but the movement in the last part of opening is quite fast and the end position is uncertain, so the sharp bottom corners of the door could end up at head height.
https://www.easygatesdirect.co.uk/store/garage-door-openers/liftmaster-garage-doors/accessories/1703e-canopy-adaptorAlso they put a lot of bending force on the top edge of the doors, and one was starting to break when we moved out.
I would suggest changing the door if it's one of them.
The door openers will take about 200 W of power. If you are getting an inverter to run one from a battery, you may need more to get the door started. However, most of the energy that a door opener uses is while it is just in standby and the radio receiver is on, so it is likely to be impractical to leave the inverter and door closer turned on if you do run it from a battery. You would need some way to isolate the battery until the door is in use, or the battery life will be a few days at most.
You might be able to fettle something to run the radio receiver straight from the battery, and only turn on the inverter when the door is moving.
It would be far easier to put a few yards of steel wire armoured cable in, which will give you light in the garage, either from a light on on the opener or with minimal further effort.
