I used a milk-crate instead of a solid box as the former provides lots of airflow to keep the inverter cool. I bought the most expensive components for this build off of an auction website for super-cheap. The entire circuit uses 10 AWG copper stand wire. I have a 30 amp fuse inside the battery box for short-circuit protection. Battery has a built-in battery-management system (BMS) as well. I keep the battery charged with an LiFePO4 charger I bought for my ebike years ago. The milk crate power station is capable of 250 Watts continuous power with 400 Watts peak power.
Components list: