The correct link cable with armouring, there are versions which are not armoured. The cable must be clipped up to the top of the heel-board above the prop-shaft, especially the non-armoured versions. If this is not done compression of the suspension can cause the prop-shaft to wear through the cable insulation with predictable results. (Image Leacy Classics)
Typical installation. This was an earlier non-armoured cable, subsequently replaced with armoured when one clamp became heavily corroded.
Massive growth around the link cable terminal on the right-hand battery. It was only when I replaced the cable that I noticed a crack in the casing by this terminal. Probably the cause, repaired using Araldite it has run for another 12 months without developing again and only a very slight reduction in electrolyte level.
The new armoured cable going to the terminal at the top left, as annoyingly it wasn't long enough to go to the other corner as on both the previous and the original link cables. The extended main battery cable from the cut-off switch now goes to the further terminal, the battery having been rotated 180 degrees. This means that the 12v terminal is now very close to the clamp bracket (circled) so care needs to be taken to maintain adequate clearance. But as both terminals on the left-hand battery are 'live' with respect to earth this is no different to the original orientation. As all the cables are black I was bothered about incorrect connection right back when I fitted twin 6v batteries. I happened to have a length of red cable from somewhere, so I cut the insulation off that in a spiral and used two lengths to wrap round the main 12v cable ...
... and the +ve end of the link cable.