A battery is used to power a load. and there is switch in between them.
How many fuses needed to protect battery and load.
Can a battery need protection?
Where do you attach the fuse?

 

Place the fuse between the battery and the switch. Only one line needs fusing.

Protecting the battery depends on how it is contained.

 

One Fuse preffered with the negative line so you it will not need to be insulated.Put it as close to the energy source as possible. Now you will need to calculate the adequate size.