What is the source of electricity in batteries?

Batteries produce electricity

An electrochemical battery produces electricity with two different metals in a chemical substance called an electrolyte. One end of the battery is attached to one of the metals, and the other end is attached to the other metal.

Explanation:

Batteries and similar devices accept, store, and release electricity on demand. Batteries use chemistry, in the form of chemical potential, to store energy, just like many other everyday energy sources. ... In a rechargeable battery, electrons and ions can move either direction through the circuit and electrolyte.

moving ball hits still ball. mover stops, hit ball moves. momentum transfer.

when two balls of the different masses are dropped from equal height, they reach the ground at the same time .this is because they experience the same acceleration.

the acceleration is independent of mass.

thus when they are dropped they will always maintain the same velocity and travel the same distance (neglect air resistance of course) at the same time.