I use a deep-discharge backup battery I keep on a charger and a 12v light and fan during power outages. So far no problems.
But someone got me thinking thinking, what if the battery runs down? Put a solar cell or several out in the sun and use them to charge during the day. What do I need to do this? Where can I conveniently buy the cell and other stuff locally? Home Depot or Lowes? No urgency or I'd Google for this, storm season is about over, but for the future.
TIA