Hi guys, me again..........

Right, i have just noticed a red wire that leads into a relay beside the left side of the battery.
The wagon works fine but its just a wonder what this wire is for?
It has a ringlet on the end so it seems it obviously fits over some screw type thing.
As i have only just noticed this, im not sure if its always been de-attached or not.

Any idea gals and guys?

Ps 87 fourtrak td