What Kind of Battery Would You Need to Power a Lightsaber?

When you think of Star Wars, what's the first image that comes to mind? Lightsabers, right? Everyone loves lightsabers. You can buy some nice replicas, and there are even classes on lightsaber training. But what about an actual working lightsaber? What it would take to make a real one?

Today, I'm going to focus on the power needed to run a lightsaber. How much power would it use, and what kind of battery would you need? (The issue of how you can make a light beam with a finite shape that slices through things … well, we'll just set that aside for now.)

For this estimation, I'm going to look at Episode I: The Phantom Menace. In an early scene, Qui-Gon Jinn (Liam Neeson) uses his lightsaber to cut through a thick metal door in a Trade Federation starship. There's a bunch of physics to consider, so let's get started.

Remember in Episode IV when Darth Vader said, “The ability to destroy a planet is insignificant next to the power of the Force”? He was talking about military power, not physical power. Words are slippery—just like the Force is not the same as a force in physics. But to a physicist, power has a specific meaning: It's the rate of energy use or transmission.

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