The trend toward ever-larger vehicle battery capacities alongside ever-smaller charger packages with maximum charging power and durability has been unstoppable for years. For end users, whether at home or on the go, fast charging and range anxiety are key criteria when choosing a charger.
As a result, technical requirements are also increasing: Higher currents and voltages need to be switched safely in confined spaces. At the same time, thermal losses must be minimized, compliance with standards like IEC 62109, IEC 61851, IEC 60947-4-1 and IEC 62955 ensured and the service life of components maximized, since chargers are expected to deliver reliable performance for many years.
Limits of conventional relays
Whether in photovoltaic systems, battery storage systems, fast charging stations or industrial energy systems, conventional relays are still commonly used to switch high currents. Although tried and tested, they often require significant space, screw terminals, complex wiring and relatively high holding power. Moreover, their high contact resistance generates heat losses, increasing the need for additional cooling.
PCB relays as a compact alternative
A newly developed relay family provides a space-saving, energy-efficient option. OMRON’s G9K series, designed for PCB mounting, cuts installation time and costs while eliminating potential wiring-related errors (Figures 1–3). Compared to DIN rail or panel mounting, PCB mounting also offers significant space savings. Low contact resistance reduces heat loss and increases energy efficiency. Robust contacts and optimized mechanics guarantee a long service life, even under high loads. Energy-efficient coils enable a lower holding current. Certain versions also support control via pulse width modulation (PWM).
With a continuous current carrying capacity of up to 300 A (AC and DC) and a switching current of up to 100 A (DC), these relays are ideal for demanding high-load applications. The broad operating temperature range, typically from -40 °C to +85 °C, allows for use across diverse environments. Thanks to international approvals, including UL, IEC and VDE, this series can be easily integrated into devices for multiple markets.
The series includes several models with additional functions tailored to specific applications. Table 1 provides an overview.
Table 1: Key technical data for the model variants
| Model | Switching configuration | Max. voltage and current | Coil voltage | Contact resistance | Special characteristics | Applications |
| G9KA | SPST-NO, double-break contact +A Aux (optional) | Up to 1,000 VAC at 300 A continuous load; 10 kV pulse strength | 12 V / 24 V DC | 0.2 mΩ (@200A 6 VDC min. 30 minutes) | Ultra-low resistance due to twin-contact design, high energy efficiency | Photovoltaic inverters, UPS systems and industrial energy storage devices. |
| G9KB | SPST-NO, bidirectional | Up to 800 VDC, 100 A | 12 V / 24 VDC | ≤ 5 mΩ | Polarity-free design, arc cut-off technology, bidirectional direct current | Focus on energy storage (DC-DC converters, DC fast chargers, solar power systems, battery storage systems, vehicle-to-grid systems) |
| G9KC | 4PST-NO + Aux (option) | 480 VAC, 40 A per pole, short-circuit-proof up to 10 kA | 12 V / 24 VDC | ≤ 6 mΩ (typ. 1 mΩ, 40 A @ 480 VAC ref. only) | Multi-phase AC switching, mirror contact | Three-phase wall boxes (up to 22 kW), HVAC systems, industrial motor controls |
Contact resistance as a critical factor
Low and stable contact resistance is crucial for all charging applications. A simulation study carried out by OMRON found that even a 1 mΩ increase in contact resistance can raise the temperature at the load connection by up to 18 °C. This not only reduces the service life of the contacts but also increases thermal stress on nearby components. Simulations demonstrate that the multipole design (G9KC) can lower the temperature rise by at least 10 °C, thereby significantly enhancing the reliability of long-lasting chargers. In practice, G9KC’s reduced heat generation enables more efficient and faster charge cycles, as the lower operating temperatures allow for decreased output current limiting (crowbar).
Summary
The G9K series offers a technically advanced, space-saving and energy-efficient alternative to conventional relays. By combining low contact resistance, high switching capacity and specific model variants, both AC and DC applications can be implemented fully in line with standards. This creates new opportunities for developers of charging infrastructures, photovoltaic systems and energy storage devices to design compact, efficient and reliable systems.
The trend toward enhanced monitoring capabilities and further miniaturization is expected to continue. The G9K series thus provides a solid technical foundation for the next generation of powerful, sustainable energy systems.
For more information and a direct ordering option, please visit our e-commerce platform at www.rutronik24.com.
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