Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of A123 Systems (Nasdaq: AONE) have popped by as much as 18% today on news that the company will be supplying batteries for General Motors (NYSE: GM).

So what: GM announced an all-electric version of the Chevrolet Spark that will debut in 2013 and be rolled out in a similar fashion to the Chevy Volt. The automaker confirmed that A123 Systems would be providing the battery for the Spark.

Now what: The Spark is a small car and would compete directly with the all-electric Nissan (OTC: NSANY) Leaf and upcoming Ford (NYSE: F) Focus Electric. The Spark also represents a big push into all-electric for GM, an initiative that the company has talked up. It will use advanced nanophosphate lithium-ion battery packs supplied by A123. It's a solid win, but I wouldn't jump in too hastily on the news as this stock still has some hurdles to clear.

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