A storage battery is a device that stores electrical energy chemically so you can use it later. Unlike regular disposable batteries that die after one use, a storage battery can be recharged hundreds or even thousands of times. When you plug in your tablet or phone to charge overnight, you're refilling its storage battery with electrical energy.

The most common type is the rechargeable lithium-ion battery found in laptops, phones, and electric cars. Car batteries are also storage batteries: they provide the burst of electricity needed to start the engine, then get recharged as you drive. Some homes use large storage batteries to save electricity from solar panels during the day so they can use it at night.

Storage batteries work through reversible chemical reactions. When the battery discharges (gives out power), chemicals inside react in one direction, releasing electricity. When you recharge it, electricity forces those same chemicals to react in reverse, storing energy again. It's like a chemical seesaw that can tip back and forth.

The invention of practical storage batteries in the 1800s transformed technology, making possible everything from submarines to flashlights to the smartphone in your pocket. Today's storage batteries are getting better every year, holding more energy in smaller, lighter packages.