This joke always bugs me because it's a spoken conversation in the context of the joke. He would say "what's an Ery?"
You have to imagine Robin has a Japanese accents so he pronounces the double consonants: bat-tery.
I also think this joke doesn’t work very well when spoken, but it is what it is
What's a tery?
Next to the 710 cap
Electric current is actually carried by a bunch of microscopic bats. A battery contains thousands of these microscopic bats. A tery is a former battery that has been depleted of its bats i.e. a dead battery.
Batteries are extremely dangerous because bats are known to carry rabies. Additionally, Harry Nyquist et. al. figured out on April 20th, 1969 that batteries with rabid bats can deliver more energy than batteries with healthy bats, so they are more dangerous now than they used to be. The bats are so rabid in home power systems that the rabies can kill you instantly if the bats get to you.
As a result, batteries may only be used in devices that cover the batteries in a protective case. Additionally, the protective cover helps shield the bats' echolocation from loud noises from outside the case so that current doesn't get lost. Actually, this effect is why telephones sound so distinct: the current-carrying bats are getting lost as they fly towards the speaker because their echolocation is being disturbed by your voice.
/joke.
He's Batman Beyond
That's funny because it was kind of an old joke made in Brazilian Portuguese and I've been seeing a lot lately. I wonder if a fellow Brazilian translated the joke.
There's a company in Winnipeg, Manitoba, called "Battery Man". Which is funny on a lot of levels. They lean into batman symbols a lot. But also, Manitoba is often abbreviated as Man (historically it was our postal abbreviation and such).
