Pila

An electric battery, as used to power such devices as a flashlight. Generally depicted as an upright, green cylinder, as a AA or D cell, with white indicators for its positive (facing up) and negative terminals.

Commonly used for various content concerning electricity, charging, energy, and power, especially in figurative senses. Its green color also suggests the icon for battery power on a cell/mobile phone.

Apple’s design includes a voltage symbol; WhatsApp’s battery is blue.