Smart Candles comes with a CR2032 3V lithium battery or one or two AAA 1.5V alkaline batteries. They'll last for between 40 and 250 hours. You can buy spare batteries in the on-line shop.

Spare CR2032 and AAA batteries will always be useful as they're commonly used in watches, cameras, calculators, card-torches, computers, digital weighing scales, torches, hand-held games, key fobs, mini fm radios, mp3 players, and toys.