Hella’s New Relay Changes Vehicle Electrical Architecture

The bistable-motor relay cuts down on battery strain and energy loss when a vehicle’s engine is not running or shut down for extended time periods.

Developed by Hella Electronics, bistable relays — also known as latching relays — are relatively new to the automotive industry, even though they are widely used by telecom companies, says Steve Hubble, president of Hella Electronics North America. “Auto manufacturers generally have wanted to use monostable relays that automatically close when the ignition is turned off.”

Bistable relays could have a tremendous impact on the design of vehicle electrical architecture, Hubble notes. They will allow greater use of telematic, “infotainment” and security systems that can operate in standby mode or be accessed by consumers while the engine is turned off.

A number of German and American auto manufacturers and suppliers have expressed an interest in Hella’s new product, Hubble says.

One of the remarkable features of the bistable relay is that it has a current-carrying capacity of 30 amperes maximum at an ambient temperature of 185 degrees Fahrenheit. Because it is a plug-in variant of the traditional automotive power relay, Hella can quickly offer this technology as a customer option.

Based on the terminal configuration of an ISO micro relay, the Hella bistable relay’s blade terminal, which is normally designated as the break- contact, acts as a third common-coil connection. To change from one switching position to another, a voltage pulse of a few milliseconds is sufficient to reset the bistable relay.

Due to the bistable switching principle, the vehicle’s battery will not be subjected to stress by additional coil power. No unnecessary power loss is generated in the relay drivers.

Production sites for Hella’s new relay switches have not yet been selected.