It was another wild week for the major auto players, one in which Fiat and Chrysler displayed the first fruits of their marriage, General Motors paid down some debt, and the suddenly very major Beijing Auto Show got under way.

Here's a look at a few stories you might have missed.

Another blow for Toyota
The bad news just doesn't seem to stop for Toyota (NYSE: TM). On Thursday, Moody's announced that it had cut the Japanese auto giant's credit rating to Aa2, Toyota's lowest level ever. The cut, which will raise the company's borrowing costs, came because of concerns over future costs related to the unintended-acceleration problems, including an anticipated $2 billion in recall costs and a worrisome question mark over potential litigation costs.

And speaking of Toyota, there's more evidence that its dramatic March sales surge was fueled by incentives: Edmunds noted this week that a stunning 71% of all Toyotas sold in the U.S. in March were financed with 0-percent-interest loans, a key part of Toyota's incentives offering. For the market as a whole during March -- a month in which most of the major automakers were pushing incentives, including "free" financing -- 22% of sales were financed interest free.

A big step forward for Tata
India's Tata Motors (NYSE: TTM) is about to open a factory dedicated to building the $2,500 Nano, the world's cheapest car. The plant, which should be online by the end of this month, will be able to produce up to 250,000 of the little cars every year.

Tata's sales goals for the Nano are extremely ambitious. If they are successful, they could pass Hyundai for second place in the Indian market, behind cheap-car powerhouse Suzuki. Early signs are promising, as Tata begins to fill some 100,000 advance orders.

But Tata will have competition shortly. Nissan is collaborating with partner Renault and local Bajaj Auto to produce what it says will be a $3,000 car by 2012. And Suzuki and Toyota are said to be stepping up efforts as well, targeting motorcycle owners looking to move to four wheels.

About that General Motors payment
On Wednesday, GM trumpeted the fact that it had paid back some $5.8 billion in bailout loans from the U.S. and Canadian governments. Some of us were less impressed than GM might have liked and there may be cause for even more skepticism. It turns out that the source of the payment wasn't GM's earnings; it was a U.S. Treasury escrow account set up as part of the bailout.

In other words, GM simply handed the government some of its own money back and called it a "payment." Not that there's anything wrong with that.

A battery breakthrough?
Here's a news tidbit that could prove to be a big deal down the road: Hitachi (NYSE: HIT) announced this week that it had developed a lithium-ion battery that used a cathode made from manganese, rather than the more commonly used cobalt. The new manganese cathodes offer two advantages. They could double the life of the battery, and manganese, unlike cobalt, is abundant.

The second issue is a major consideration. Several rare earth metals are critical to the manufacture of hybrid and electric cars, but the supply is limited, and nearly all of it is controlled by China. That is expected to change in time. The U.S. has abundant rare earth resources and expertise, but needs to build out the infrastructure to mine and refine them; it has been a point of concern, with some observers suggesting that the U.S. is merely trading one foreign dependence (on oil) for another.

The very big Beijing Auto Show
Just a few years ago, the Beijing Auto Show was a minor stop on the global auto show circuit, but just like the Chinese auto market, it has grown by leaps and bounds, becoming a key venue for manufacturers unveiling new models. Along with a number of new and revised production models, Ford (NYSE: F) continued its China push, showcasing a new three-cylinder turbocharged engine in a concept called the Start, a small, sleek "urban" car.

In addition, Honda (NYSE: HMC) is set to announce a new high-end model to be produced via its joint venture with Guangzhou Auto. BYD, the Chinese company backed by Berkshire Hathaway (NYSE: BRK-B), will show the e6, the electric five-seater it expects to bring to the U.S. later this year.

Another step forward for Tesla
Tesla Motors, the Silicon Valley electric-auto maker with dreams of mass production, took another step as it announced the delivery of the first batteries for its upcoming Model S sedan. The batteries, made by Panasonic (NYSE: PC) and originally designed for laptops, are the highest energy density battery cells currently being produced.

Tesla is the only automaker using these small batteries. While major auto suppliers Johnson Controls and Magna are working to produce large-format batteries specifically designed for automotive use, none are yet in mass production. Apparently, Tesla doesn't want to wait.

Fool contributor John Rosevear owns shares of Ford. Berkshire Hathaway is a Motley Fool Inside Value choice. Berkshire Hathaway and Ford Motor are Motley Fool Stock Advisor selections. The Fool owns shares of Berkshire Hathaway. Try any of our Foolish newsletters today, free for 30 days. The Motley Fool has a disclosure policy.