The puzzle is almost complete: General Motors and Honda have signed an agreement to work on the future of fuel cell technology.

They're the latest large automakers to announce a fuel cell technology share agreement, as car companies continue to explore the future of alternative propulsion.

GM and Honda are calling it a "long-term, definitive master agreement to co-develop next-generation fuel cell system and hydrogen storage technologies, aiming for the 2020 time frame."

That's longer term than the 2015-2017 discussed by several other collaborating manufacturers, including Toyota--whose first production fuel cell vehicle is expected to debut at this November's Tokyo Motor Show, for sales some time in 2014.

Toyota will develop future fuel cell vehicles with German automaker BMW--once in negotiations of its own with GM for the same reasons.

Meanwhile, Daimler, Ford and the Renault-Nissan Alliance have their own fuel cell technology development plans, with eventual production cars expected in "2017 or later".

That major automakers are rushing to find fuel cell partners like teens looking for a prom date isn't much of a surprise.

Developing fuel cells is as hugely expensive and risky as it ever was, yet few automakers can afford to be left out of the loop should the technology suddenly take off.

Having fuel cell development on the back-burner is simply insurance for changing future trends, as much so as electric cars are for reluctant companies like Fiat and Chrysler. But unlike electric cars, which are relatively uncomplicated, the huge cost of fuel cell development makes partnerships the only real financially-viable way of exploring the technology.

For GM and Honda, it's a chance to share expertise, as much as costs--between the two companies are over 1,200 fuel cell patents, filed from 2002 to 2012.

GM alone has accumulated more than 3 million miles of fuel cell testing, while Honda has for several years run a trial fleet of FCX Clarity fuel-cell vehicles in real-world testing. A successor to the Clarity is expected in 2015, while GM is yet to announce a production car using the tech.

Which automaker will be next to explore fuel cells? Place your bets...


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