Lemon battery

You will need:

Copper - Coin

Better ordinary wire

Zinc - Carnation

From 1 lemon - 1 Volt (In a regular finger battery 1.5 Volt)

From 2 lemons - 1.8 Volts (A little more than in a regular battery)

From 4 lemons - 3.5 Volts (You can connect a light bulb)

Good luck

Source: youtube.com