Definitely disconnect your battery ( negative side) . Have some heat shrink tubing to slide on before joining and stagger the joint over a few inches otherwise you will end up with a large bulge of the cable in one place.
Tony.
ps. This may be obvious so no offence if you're aware.![Wink ;) ;)](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
Tony.
ps. This may be obvious so no offence if you're aware.