The proportion of electrically powered vehicles is growing worldwide. At the same time, the focus is shifting to the performance and safety requirements of the electronic components used. With its innovative and high-performance relays, Gruner AG offers a wide range of solutions for global mobility, from low-current to high-voltage applications. New approaches in simulation underline the future orientation of the southern German medium-sized company, which will be presenting its innovations live at the Battery Show in Stuttgart from June 3 to 5, 2025.

For a long time, it was one of the biggest problems in the nationwide infrastructure of electromobility: charging. This problem is now largely a thing of the past. In addition to an increased number of charging stations, there is also a noticeable trend among vehicle battery manufacturers towards greatly increased efficiency – and more power.

“Our new bank charging relay type 860 is the perfect solution for this”, explains Markus Rekla, team leader of the high-voltage development team at Gruner AG. Modern charging architecture in electric cars charging at both 450V and 800V. One technical option for enabling charging at both 450V and 800V is to switch two battery banks in the vehicle from series connection to parallel connection. Type 860 relays can be used for the switchover. “Our relays not only meet the requirements for low power consumption during normal operation but also provide reliable performance in terms of short-circuit current carrying capacity and shock resistance in unintended emergency situations.”

The lowest possible contact resistance is required to reduce heat generation during operation. A solenoid is used in the relay for this purpose, which holds the contacts together via a spring. “The design of the components is always a balancing act between assembly space and power losses”, explains Rekla. “A larger drive ensures a lower contact resistance, but also requires more space. The aspect of contact force must also be considered from the perspective of a possible fault. After all, we are talking about short-circuit currents of up to 16,000 amperes. It is obvious that maximum safety requirements apply here.”

In addition to conducting the current as smoothly as possible, the high-voltage relay also had to meet the highest requirements in terms of shock stability and load capacity in the event of a short circuit. The Gruner development team relied on a principle that has already proven itself in Gruner’s 12 and 48V relays: The physical principle of Lorenz force is used on the one hand, and the specific advantages of the relay layout with C-bracket, spring lever and intelligent cable routing on the other. “Put simply, the forces acting on our relay in the event of an accident or mechanical shock balance each other out”, says Rekla. “As a result, the relay remains reliably open or closed even in the event of a fault.”
The high-voltage relay type 860 therefore combines several technological advantages to create a pioneering solution. Added to this is the flat design of the Gruner relay – another strong argument for automotive manufacturers worldwide.

Simulations in the high-current range

The bank charging relay type 860 illustrates Gruner AG’s development expertise. This is also evident in another technological field: in the simulation of electric arcs, which the medium-sized company from southern Germany has strongly promoted. Electric arcs release extremely high levels of energy and are therefore extremely difficult to switch off.

“When simulating electric arcs, two worlds have to be combined”, explains Markus Rekla. “On the one hand, electricity and magnetism. On the other hand, thermodynamics and fluid mechanics, as gases are also released during the arc. This is extremely demanding, you could say it’s the top tier of simulation.” This research and development work is an important building block on Gruner AG’s path to transferring its expertise from bank relays to HV main relays. Here, the development team also benefits from its many years of expertise in the field of solenoids.

Powerful relay solutions for 12V networks

In addition to innovations in the high-voltage sector, Gruner is also a sought-after partner to the automotive industry in the low-current sector. This includes relays for use in power distribution boxes. “With the 753 and 754 relays, we have powerful solutions at the start with which we are successful not only in Europe, but also in Asia and the USA”, explains Robert Frank, Key Account Manager Automotive at Gruner.

The 760 relay ensures functional safety in lithium-ion starter batteries. “Our relays are in demand wherever high currents need to be carried, high shortcircuit currents need to be galvanically isolated, high shock resistance needs to be guaranteed and intelligent monitoring functions need to be mapped.” This ranges from the status of the relay – open or closed – to temperature monitoring. “The focus is on the long lifetime of the battery, but above all on the safety of the driver and the protection of the vehicle.”

Focus on light mobility

In addition to electric cars, “light vehicles” such as battery-powered scooters, pedelecs, motorcycles, tuck-tucks, leisure and fun vehicles on two or three wheels are playing an increasingly important role, especially in regions with a high population density. The voltage range here is 48 or 96 V. “This voltage load in turn significantly increases the demands on the relays for switching and disconnecting the lithium-ion battery supplies in the event of faults and accidents”, points out Robert Frank. “This is precisely why Gruner AG has developed new 48 V and 96 V relays.”

The 853 model is capable of carrying a rated current of 120 A at 48 V DC and the 854 model can carry a rated current of 120 A at 100 V DC continuously and safely disconnect it. Both can also safely isolate short-circuit currents of up to 3kA and have a shock resistance of up to 50 g. In addition, the new relays offer important monitoring functions such as contact or temperature monitoring, which are made possible by an internal NTC.
Experience Gruner in person at the Battery Show

The innovative solutions underline Gruner’s position as a technology and global market leader in the field of relays for energy and battery management. At the Battery Show in Stuttgart from June 3 to 5, interested parties will have the opportunity to see the new relays live at the Gruner stand and to talk to contacts from development and sales in person. The industry pioneer will also be showcasing electromagnets for the automotive sector – and thus the comprehensive portfolio that Gruner can offer for this industry.

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