I thought about building a gravity battery in my yard.

The math is E = mgh. Not complicated. I think the conclusion was that to charge my cell phone from zero to 100% I would have to lower 1, 000 pounds from a height of 100 feet. Had to make some assumptions about my phone battery capacity... But still... Wildly inefficient.

That was before losses and this video says the building is 80% efficiency.

So whenever I see one of these grav batts actually being built, I wonder if they checked? I mean, it has some capacity but will it ever be worth the construction costs?