Red Bull is using an innovative super-compact KERS system this year, according to the latest paddock rumour.
After Sebastian Vettel powered to a dominant pole in Melbourne late on Saturday, FIA press conference moderator James Allen told the reigning world champion he had not noticed him pressing a KERS button during qualifing.
"We didn't use it in qualifying, that's correct," answered the German.
Asked why, Vettel said bluntly: "Not fully charged."
We didn't run it today for reasons we will keep in the team.
But while Lewis Hamilton not using KERS during Q3 at Albert Park was due to a failure in his Mercedes unit, it emerged that Vettel's teammate Mark Webber also not using KERS may have been for tactical reasons.
"We didn't run it today for reasons we will keep in the team," said the Australian.
It is rumoured that Red Bull's KERS may be solely for use at the start of a race, with the unit charged in the garage rather than under braking while the car is running.
The 'start-only' KERS could theoretically be smaller and lighter, while not affecting the handling on track because the battery is not charged while the car is braking.