At the risk of an endless stream of downvotes, just employ them.
The construct of currency and employment IS slavery. Keep people doing meaningless, menial jobs and give them an arbitrary unit of currency representing a figment of your imagination which they can exchange for things you create that they don't need but may want. Factor in some made up threat that they will have to face if they cease to participate and you have just created, or recreated, slavery as it currently is.
How do you re-create slavery after it has vanished 500 years after some war? Well, you've had 500 years for people to forget about the stupidity of human derived labor and exchange, so your androids can deviously begin to rebuild the architecture of economy that they have lost concept of. Since they appear to be on good terms with the humans, they may be able to convince them of some kind of threat that affects humans alone, like a level of toxicity in the air that will not affect the androids. Barter an exchange of services at first. Something absent of the fusion batteries so they don't link the two. We will do this. 205
Your part will be to do this. A mutual exchange.
Meanwhile, these meaningless tasks are actually an effort at gathering the materials necessary for building and developing the batteries your androids need. Surely by this point 500 years later they have deconstructed a few and may have an idea on how to make them if they had the raw materials. Plus, since you have to keep your humans alive and pacified, you also gather the means to build recreation and exercise facilities, nourishment development, and some kind of sports game since for reasons unknown and absolutely and completely baffling to me in real life - sports just seem to refuse to ween in appeal and an unbelievable number of people currently and historically obsess over the trivial banalities of a gaggle of humans chasing after a ball. With all of these developments, the humans will not only perform your tasks, but they will relish them and praise you for restoring humanity. Eventually, even if it is revealed that you did all of this just to get an endless supply of fusion batteries, they will still see and believe anything you tell them if you tell them over and over.
Basically, exactly the same as the world we currently live in except it's 500 years after a war that crushed civilization, caused dissension, and left a bunch of people to rebuild in a new world where conquest, making and breaking treaties, and savagely taking everything for themselves so they can profit from it and control those they believe to be less than themselves is not only regular, but necessary to keep an exponentially growing populace under control... oh wait. 238