NASHVILLE -- Have you ever been inside a car plant? No? Well, it’s a lot of fun, even though they make you wear eye protection and, frequently, a hard hat. On Wednesday, I toured the giant Nissan plant in Smyrna, Tennessee, where they bolt together Pathfinders, Altimas and Xterras.

I was there to attend the groundbreaking of the $1 billion, 1.2 million square-foot lithium-ion battery plant that Nissan is building to supply the ultra-cool electric Leaf (due at the end of the year). The Leaf is $32,000, but there’s a $7,500 federal tax credit and if you’re lucky enough to live in California you can get one for $20,000. Some 13,000 of our fellow citizens have signed up on the Internet and paid $99 to reserve Leafs.

The ceremony was OK, but we’ve all heard politicians talk about how much they’re doing for their state and for the United States of America. The factory tour was really interesting, because this is the largest auto plant under one roof in the U.S., capable of producing half a million cars annually, 2,100 a day and one every 27 seconds. The plant covers a mind-boggling 5.2 million square feet, and its cafeteria serves 4,500 lunches a day. Do my notes say something about 2,000 hamburgers and 1,100 soft drinks?

We drove through in an electric tram, with the main obstacle being multiple fork lifts (soon to switch to fuel-cell power; this is a very green plant). We motored past displays of “Job 1” for a number of vehicles, including the ’93 Altima and the ’03 Pathfinder. And then we came to the station where they install the gas tank. First, take a look at the video:

I might find it hard to do that every day, but my point is elsewhere. The Leaf will be built on existing production lines at Smyrna. Battery packs will go into the Leafs the same way gas tanks do -- they’ll swing into place and be bolted in with a few quick jabs of the electric wrench.

Here, Carlos Tavares, Nissan’s chief for the Americas, explains how it’s all going to work:

Manufacturing executive Mark Swenson told me the battery factory will open in the early fall of 2012, following a year of construction, equipment installation and trials. The Smyrna factory will be producing Leafs around then, too. “We’re going to make the battery plant as environmentally friendly as we can,” he said. “We’re looking at solar panels to offset energy use.”

Until Smyrna is up and running, Nissan Leafs will be supplied from Japan. I can’t wait to get my hands on one. The car driven onto the tarmac by Nissan CEO Carlos Ghosn was a barely functional prototype.  I can say it has pretty good rear-seat legroom, however, and a neat GPS/user interface.

You want a prediction? I think the Nissan Leaf will be at least modestly successful, justifying the company (and Ghosn's) enormous investment as a first-responder in the green car wars. History will record the Leaf as the first mainstream battery car, and if I'm right about cars plugging in, that could make it as significant as the Model T.