Batteries are everywhere — they’re in our phones, our computers, our cars, our toys. But how do they work?

To find out, we talk to a scientist who’s making really big batteries to store renewable energy, another who’s working on really small ones to power our phones, and we play in a park with a dog. All that, plus the mystery sound!

Want to hear more about electricity? Listen to the rest of our Electricity series:

Part 1: Shocking! The science of static

Part 2: High voltage! How electric power reaches your outlet

Part 3: Charged up! The science of batteries

Part 4: The nerve! Electricity in our bodies

Brains On! is an award-winning audio show for kids and families from American Public Media.