I notice from most images that the Abrams has a cable running inboard from the rear right-hand light to the hull plate. What I cannot work out is why this is not repeated on the left-hand one. Is this a standard feature of all Abrams tanks?

Maybe due to the battery compartment on the right hand side?

I think Mark is on the right track. The location where the cable enters the hull is also the cable entry point for the the original APU that mounted on that corner of the hull and tied directly into the batteries. I'm guessing they used the same hole for the taillight cable for convenience sake.

Sean

addendum: looking thru more photos and this same cable routing setup appears on vehicles without provisions for mounting the APU as well so maybe that's not quite the answer. There are a number of other posters who are more up on the Abrams and hopefully they can point us in the right direction.