BMW release KERS investigation findings

Following what BMW described as an "extremely far-reaching analysis" into the incident, which occured when the mechanic collapsed to the ground at Jerez as he attempted to wheel a car fitted with the device back into its pitbay.

"The mechanic suffered an electric shock after touching the sidepod and steering wheel of the car," said BMW's head of powertrain development Markus Duesmann.

"There was a high frequency AC voltage between these contact points, the cause of which has been traced back to the KERS control unit and a sporadic capacitive coupling from the high-voltage network to the 12-volt network," he added. "The voltage ran through the wiring of the 12-volt network to the steering wheel and through the carbon chassis back to the control unit.

"Only a small amount of energy can be transferred through this capacitive coupling effect. However, the energy is sufficient to cause an extremely painful reaction.

"The driver was insulated against the car by his racing overalls and gloves and therefore not in any danger."

BMW Sauber will make the findings of their investigation available to the teams at next week's Technical Working Group meeting and have already supplied a copy of them to the FIA.

"In addition to the measures required to tackle the issue at hand, the extremely far-reaching analysis we conducted also gave rise to other recommendations which are of great value for the development of electric KERS systems," said Duesmann. "Among the measures arrived at are changes in the design of the control unit to avoid capacitive coupling effects, extended monitoring functions for high frequencies and a conductive connection of the chassis components to avoid any electric potential."

Duesmann explained that the results of the investigation took so long time to conclude its findings because of the complicated nature of the new system, which is set to be introduced to Formula One as part of the 2009 technical regulations.

"It was not possible initially to reproduce the capacitive coupling effect in the car, as the problem was caused by a sporadic error in the control unit," he explained. "Due to the extremely high frequency of the voltage in the steering wheel, the safety mechanisms and data recordings did not pick up on the error.

"In the absence of data, all the theoretical possibilities had to be systematically investigated and analysed in tests.

"Furthermore, the capacitive coupling effect only occurs under certain conditions. Without the option of driving the KERS test car used in Jerez again, we had to reconstruct these conditions."

BMW has made it clear they will not test the system again until a safe solution to the problem is in place.

"We will resume the testing programme once all the necessary amendments to the safety concept have been implemented," said Duesmann. "We expect this to be the case in the autumn."