Is Tesla working on a new type of hybrid pack that combines two different battery technologies to deliver a huge increase in range? This question has been floating around the discussion groups for a few months, but several outlets reported it as breaking news this week after a couple of stock analysts discovered the story (by the way, TSLA set a new record this week, closing over $183 a share).

Tesla has filed at least eight patents on applications of metal-air battery technology, as Green Car Reports’ John Voelcker reported in April. One of these, “Efficient Dual Source Battery Pack System for an Electric Vehicle,” envisions two battery packs working together. An extract from the application:

A method of optimizing the operation of the power source of an electric vehicle is provided, where the power source is comprised of a first battery pack (e.g., a non-metal-air battery pack) and a second battery pack (e.g., a metal-air battery pack).

The power source is optimized to minimize use of the least efficient battery pack (e.g., the second battery pack) while ensuring that the electric vehicle has sufficient power to traverse the expected travel distance before the next battery charging cycle.

Metal-air batteries have high energy density but low power density, while lithium-ion batteries offer the reverse, so a hybrid system could theoretically leverage the strengths of both to maximize range and performance.

As a commenter on AutoBlog Green noted, ultracapacitors, which feature virtually unlimited cycle life and great power density, could also be added to the mix. This idea parallels the paradigm of tiered computer storage, which employs expensive but fast cache memory, cheaper RAM and super-cheap high-capacity hard drives.

None of this is exactly news, but it is particularly relevant at the moment, as GM has acknowledged that automakers are “in a race” to develop better batteries, and Elon Musk has said that a “truly gargantuan battery factory” will be needed within a few years to meet ballooning demand.

Tesla isn’t the only company working on metal-air batteries. According to MIT Technology Review, Toyota is focusing research efforts on them too.

Trip Chowdhry of Equity Research told Benzinga that metal-air batteries could one day account for 40 percent of the market. “I don’t think Panasonic or even Samsung could be a leader in the metal-air battery [production],” said Chowdhry. “I think there could be some other players, [but] we don’t know who it is.”

Sources: AutoBlog Green, Benzinga, Green Car Reports, MIT Technology Review