I am not a physicist, and I don't understand the details of electromagnetism. Anyhow, I was looking for how the batteries work in Google. So, I came across this article: "How batteries work: A gravitational analog" by Dana Roberts.
In the abstract, she said something about "gravitational cell". Then she gave a lot of technical words that I could not understand. I was going to read the whole article, but I don't have account for AJP. So, I don't have access for this article.
My question here is: What is the "gravitational cell"? Please, explain it to me in detail with some illustrations.
Just to let you know, I found the full article here