If your load is under 500W you can buy a turnkey EcoFlow/Bluetti/GoalZero system and just plug it in.
As another example application, I have to replace a 10 ft by 6.5 ft backyard shed, and would like to mount one or two panels on the roof for purpose of lighting, re-charging outdoor tools, etc., with no connection to house or the grid.
There are a sea of these on youtube, and many ways to built lithium battery packs from Ebay surplus scooter and ebike packs. Buy and build with Japanese or Korean tubular cells. The ones that started fires were lower grade cells from other countries. You can also buy 12 volt lithium car battery drop in replacements = $$$. That said, put the battery pack in a gasket sealed steel case = snuffs any lithium fires by oxygen starvation for a worst case. For the task you describe 1 or 2 lithium car batteries should do