That fuse does not look very 'blown'. The normal faults on this sort of thing usually result in the fuse wire exploding violently. Replace the fuse and it will likely work. The fuse value is stamped on the end cap, but you can't see it as that side is facing the PCB, remove the fuse and it will say.
To test safely without wasting money on fancy fuses, wire a 100W lightbulb in place of the fuse, if there is a fault the bulb will light brightly, but there will be no explosions. If the charger is OK, the bulb may light briefly, or dimly, and the charger should power. Don't attempt to charge a battery with the bulb in place. I have a Makita 10.8V charger here, the fuse is 3.15A, which is also helpfully printed on the PCB.