Either way, without firing this thing up every couple months or so, it wouldn't turn over if you hooked it to a nuclear reactor. After 15 years with no maintenance, and it was abandoned rather than carefully put away, you'd have zero chance of this being anything other than a heavy paperweight. batteries in an iPhone aren't even worth discussing, they barely hold a charge when unplugged for a few hours. Be a pretty impressive battery indeed to hold a charge for 15 years. I'd doubt you could get it to TAKE a charge after that long, even if the power came back on for good...
I've fired up a lawn mower that's sat idle for several years.
But generally you're right. Like I said earlier these small inconsistencies don't get under my nerves any more than why the grass is cut at the prison in the Walking Dead.
BTW, did the inconsistencies in Trek drive you irk you as well? I was watching and old TNG episode Force of Nature
and the species that was concnerned about warp field energy destroying their space and altering their plants gravity had an amazing piece of technology.
They could completely disable a star ship with their special vertaron [sp?] beams but that technology was never to be heard of or seen again when the enterprise is in battle and could have used the same technology to disable a combatant.