Sensor shuts off HV battery during accident

February 09, 2011 // Christoph Hammerschmidt

Automotive supplier Continental has developed a sensor (satellite) for electric and plug-in hybrid vehicles which will immediately shut off the high-voltage battery in the event of a collision while the vehicle is in charge mode. Thus, emergency service personnel can recover vehicles without running the risk of suffering 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, the company explained. The major benefit of the 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. Electric vehicles and plug-in hybrids are powered by high-voltage batteries of up to 400 volts.

The evSAT sensor is only active during charging cycles. Otherwise, the airbag sensor assumes the task of switching off the battery in the case of an accident.

'evSAT' stands for 'Satellite for Electric Vehicles' and essentially consists of an independent triaxial sensor with a CAN interface. During the charge phase, other relevant vehicle electronics systems, including the airbag system are not operational.

Thus, in order 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.

The evSAT sensor is designed as a triaxial  acceleration sensor with CAN interface.

Most high-voltage batteries in electric or plug-in hybrid vehicles generate a potentially fatal voltage of 400 volts. In the US, there is already a legal requirement for the vehicle power supply voltage to fall to below 60 volts within five seconds of an accident occurring. No such laws exist yet in Europe. "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", said Telmo Glaser, Continental's evSAT project manager.

The evSAT sensor 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 there is no need for the conventionally powered vehicle variants within a model series to be modified. evSAT can be integrated into existing systems of electrically powered vehicle variants without redesign work.

evSAT will go into series production with a major German vehicle manufacturer in 2012, Continental said.

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December 15, 2011 | Texas instruments | 222901974

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