Conti sensor helps EV users avoid a shocking experience

Many batteries in electric or plug-in hybrid vehicles generate some 400 volts, almost twice the voltage employed in standard domestic plug sockets and enough to give a potentially fatal jolt. Vehicle occupants risk exposure to this electric charge in the event of an accident, and US legislators have already stipulated that vehicle power supply voltage must drop to below 60 volts within five seconds of an accident occurring. No comparable laws yet exist in European markets, yet Germany’s Continental is switched onto the challenge of reducing electric vehicle battery voltage to safer levels following a collision. The automotive supplier has now come up with the evSAT, a sensor that will immediately shut off high-voltage batteries in the event of a collision while the vehicle is in charge mode, enabling emergency service personnel to recover the vehicle without the risk of receiving an electric shock.

“The evSAT acceleration sensor is active in charge mode; it detects an accident and passes this information on to the battery management system which then shuts off the high-voltage battery”, said Dr. Axel Gesell, senior manager platform development Sensors & Satellites, which is part of the Passive Safety and ADAS business unit of Continental’s Chassis & Safety Division. “The major benefit of our product is that it prevents fire and rescue service personnel sustaining high-voltage injuries when coming into contact with vehicle metal parts or if they have to cut through the vehicle to recover accident victims”. The evSAT will be manufactured at Continental’s Regensburg factory in southern Germany and go into series production with a major German vehicle manufacturer in 2012.

Those with an interest in acronyms will be pleased to learn that ‘evSAT’ stands for ‘Satellite for Electric Vehicles’; Continental explains that the technology employed in evSAT essentially consists of an independent, triaxial sensor with a CAN interface. During the charge phase, the other vehicle electronics, including the airbag system are not operational. To avoid the considerable expense of adapting the airbag system to meet new requirements, Continental has developed evSAT for the vehicle’s charge mode. The accelerator sensor employs an algorithm to detect a frontal, rear or side collision with another vehicle and immediately transmits a signal via the CAN interface to the battery management system which then switches off the battery within half a second. evSAT reacts in the same way if it detects a rollover in driving mode. In this case, the battery is deactivated within four seconds at most. In the event of other types of driving accident, evSAT remains inactive. In such cases, the airbag system assumes the task of cutting off the battery. If the electric or plug-in hybrid vehicle has been switched off and is not being charged, the evSAT moves to a standby mode to prevent the battery discharging. As such, evSAT represents an additional passive safety system function for electric and plug-in hybrid vehicles.

“As electromobility continues to develop, the safety of electric vehicles will assume an increasingly important role. The need for technologies to meet future challenges is already demonstrated by the additional demand for evSAT from numerous other vehicle manufacturers”, commented Telmo Glaser, Continental’s evSAT project manager.

Continental says that evSAT can be installed in a number of different places in the vehicle; it should, however, be placed sufficiently well inside the vehicle (beneath the front passenger seat, for example) to avoid being damaged in an accident. An advantage of using evSAT is that it removes the need to modify conventionally powered variants within a vehicle model series as evSAT can be integrated into the existing systems of electrically powered vehicle variants without redesign work.