JMHO, you actually have two power sources on this wire, the battery and the alternator. To protect this wire you need a fuse (or other type of protection device) at both ends.
Some will argue this wire does not require any protection, as the older vehicles didn't have them. However, as current loads increased this wire became protected to prevent electrical fires. Usually OEM used fuseable links at each end as they are compact. This wire can be ordered from OEM with the links installed for the appropriate current, also available in some cases from summit and jegs.