gravity battery

2 Articles

Power From Gravity

May 26, 2026 by 64 Comments

Gravity batteries aren’t exactly a new idea. You can store energy by lifting something heavy, converting kinetic energy into potential energy. To get it back, you let the mass fall and convert that motion to electricity. [Valeriamayara22] shows how to build a working demonstration model of such a system.

This isn’t free energy. Something has to lift the weight. In this case, the height is 1.8 meters, and the mass is 15.65 kg. Even so, the model achieves 13 W peak output and 58% efficiency, according to the post. Reportedly, it takes 394 drops of the weight to fully charge an iPhone 16, so this isn’t a practical project, but it does show how a gravity battery works. One nice thing is that the system stores as much energy on its 1,000,000 th charge as it does on the first one, especially if you keep the chain lubricated. Try that with a chemical battery.

The mechanical part uses a bicycle chain and some sprockets. There is a battery to even things out since, like wind power, when you make energy with a mechanical battery, you either use it now or lose it.

The cost of the build is about $400, and there’s a GitHub repo with all the files if you want to take your own shot at it. The energy efficiency number references the potential energy stored versus the energy produced. Obviously, if you are using some other energy source to lift the weight, that’s another calculation.

As you might expect, a practical system like this can be very large.

The 19th Century, When Gravity Battery Meant Something Different

May 16, 2020 by 19 Comments

The internet is full of dubious content promoting “free energy” devices and other ideas that stretch credibility, so [Robert Murray-Smith] prefaces his demonstration of a gravity battery with a warning to look elsewhere if you are in search of such things. Instead he’s showing us a pair of cells from The Model Engineer and Amateur Electrician, a printed periodical that sounds to us something like an equivalent of Hackaday from the 1890s. (Video embedded below.)

The cells are termed gravity batteries because their constituents settle out into layers not unlike a tequila sunrise under the influence of gravity, something that made them especially suitable for the home constructor in the late 19th century when there were no handy wall outlets from which to snag a bit of power.

The chemistry of each is not unexpected if you spent any time in your high school’s lab, a zinc-copper primary cell with a zinc sulphate/copper sulphate electrolyte and a secondary zinc-carbon cell with a zinc bromide electrolyte and a layer of bromine forming on charging. The construction in large glass vessels is archaic though, and it’s this that’s prompted his video. He poses the question whether this type of cell might be revived using 21st century techniques to produce something of use today. The video is below the break, and even if you are not about to try your hand at electrochemistry it’s an interesting watch.

Thanks [Blaubär] for the tip! Continue reading “The 19th Century, When Gravity Battery Meant Something Different” →