Batteries & Power Supplies

Where the electrons come from.

A battery converts stored chemical energy into electrical energy, maintaining a voltage difference between its two terminals until it's depleted.

• Voltage tells you the electrical pressure available (1.5V for a AA cell, 9V for a PP3 block).
• Capacity, in milliamp-hours (mAh), tells you roughly how long it can sustain a given current.
• A regulated power supply (like a USB adapter) holds a steady output voltage regardless of the current your circuit draws, within its rated limit.