Battery power may be the front-runner to become the car technology of the future, but don't rule out the underdog hydrogen.

That's the view of some major automakers, including BMW and Audi, which are developing hydrogen fuel-cell passenger vehicle prototypes alongside their fleets of battery cars as part of preparations to abandon fossil fuels.

They are hedging their bets, calculating that a change in political winds could shift the balance toward hydrogen in an industry shaped by early-mover Tesla's decision to take the battery-powered road to clean cars.