There are three different locations that we recommend installing fuses or breakers.
Fuse between solar panel and charge controller.
Class t fuses are used as circuit protection between a battery bank and an inverter.
Maxi fuses provide circuit protection typically between a charge controller or small inverter and a battery bank.
As an example blue sky recommends a 60 amp fuse breaker for their solar.
Mini fuses are typically used for small system components like battery management systems or monitors.
With a pulse width modulated pwn charge controller the worst case amps flowing to and from the controller are the same so the fuse and wire size can match.
With 10a fuse you could deliver 120w before it breaks.
The load terminal of the solar controller can be connected with a dc power device which is the same working voltage as the rated voltage of the battery and the controller supplies power to the load with the battery voltage connect the positive and negative poles of the load to the load terminals of the controller there may be voltage on the load side please be careful to avoid a short circuit when connecting the load a fuse should be connected to the positive or negative cord of the load.
I guess the fuse it ment to safeguard the solar charger if you by accident should short the wires or swap the wires on the battery.
First between the charge controller and battery bank second between the charge controller and solar panels and third would be between the battery bank and inverter to determine the fuse size needed between the charge controller and battery bank you simply match the amperage rating on the charge controller.
Jst ensure you use appropriate wire gauge.