Here is helpful information about the battery pack for the Scout 3 / Scout 4 scooter 12Ah battery pack.
The internal fuse is designed to prevent a spark or fire in the event the batteries are wired incorrectly. In the event the batteries are mis-wired, at the moment of connection of the last wire, the fuse would blow. Once the fuse blows, the battery pack isn't going to work and the scooter is going to appear completely dead until the batteries are connected properly AND the fuse is replaced.
Inspecting and replacing the fuse
The fuse is encased in shrink-wrapped plastic. To inspect and replace it, the plastic wrap needs to be cut away with a knife.
The fuse has been unplugged for inspection. This fuse is good. If the fuse were blown, the U-shaped metal strip would appear melted through. In that case, it should be replaced with a 40 amp automotive-style blade fuse available from any auto-parts store.
Proper battery connections
Here is how the batteries should be connected inside this battery pack.