So yeah.. it's as dumb as it sounds but...
If a mecha vampire is a thing what would you think it would be?
Eleventy-Zero slowly powered up.
The macrophage that had been released upon the world has destroyed most of the Zircon-Thorian reactors and rebuilding the cyrstal latuses that allowed that to work was impossible, given the current state of the world. The planet had been glutted on free energy, and with no energy restraints, there were no limits on most projects. Most of the human race has switched over to immortal bodies of mechanical design. Fortunately, while the age of free energy was dead, the Everlife batteries which had a 99.7% efficency still functioned. A compromise was made, and most humans wound up powering down for long periods of time, only to rise up when their batteries had been refilled on what little energy rations they were allowed.
This has resulted in a social strata, the day-mechs were those who could afford the ultra-expensive solar collectors. These mechs could find enough power to function during the day, then they would be forced to slumber at night, but this still made them far more active then most of the population, who might rise from recharge slumber once a month, or even once a year, in some cases.
Then there were those who didn't want to.
They became the night-walkers. The Vampiric-Mechs who instead of having access to Solar collectors, instead chose the path of power vampirism. At first they were just using illegal energy taps, but as those places became fewer and harder to find, they began the unthinkable.
The direct draining of other mechs.
And so the energy vampires took to the night, seeking easy prey in an ever-increasingly desperate attempt to remain one step ahead of the law.
The Sun had slipped below the horizon.
Eleventy-Zero would soon venture out to FEED.