The solar panel, battery, and load are all in parallel. Like this: https://www.circuitlab.com/editor/#?id=swpddv https://www.circuitlab.com/editor/#?id=swpddv

The solar panel, battery, and load are all in parallel. Like this: https://www.circuitlab.com/editor/#?id=swpddv https://www.circuitlab.com/editor/#?id=swpddv There's probably some charge control electronics, but that's the gist of things. When the battery is discharged or shorted, the solar panel would need to raise the voltage to power the load. When the battery fails as an open circuit, the solar panel can power the load directly.