The **MAH78FAG-R** is a high-performance, high-voltage automotive-grade relay manufactured by **Fujitsu Components**. It is specifically designed for Power Distribution Units (PDUs) and Battery Management Systems (BMS) in Electric Vehicles (EV) and Hybrid Electric Vehicles (HEV). --- ### ## Technical Specifications The following table outlines the key electronic parameters of the MAH78FAG-R: | Parameter | Specification | | :--- | :--- | | **Contact Arrangement** | 1 Form A (SPST-NO) | | **Max Switching Voltage** | 450 VDC | | **Rated Load Current** | 30A (Continuous) / 40A (Short term) | | **Coil Voltage (Nominal)** | 12 VDC | | **Contact Resistance** | Max 2.0 mΩ (at 20A) | | **Dielectric Strength** | 2,500 VAC (between coil and contacts) | | **Operating Temperature** | -40°C to +85°C | | **Mounting Type** | PCB Through-hole | --- ### ## Core Electronic Features ### 1. High Voltage Handling The relay is engineered to handle DC voltages up to **450V**. In DC switching, arc suppression is a critical challenge; the MAH78FAG-R utilizes specialized internal gas filling or magnetic blowout structures to safely extinguish arcs when the contacts open. ### 2. Compact High-Capacity Design Despite its ability to switch high power, the "MAH" series is known for a reduced footprint compared to traditional industrial contactors. This makes it ideal for dense automotive PCB layouts. ### 3. Automotive Grade Durability * **Vibration Resistance:** Built to withstand the constant mechanical stress of a moving vehicle. * **Sealed Construction:** Typically plastic-sealed to prevent the ingress of dust and moisture, ensuring long-term reliability of the contact surfaces. --- ### ## Common Applications * **Pre-charge Circuits:** Used to limit the inrush current to the motor controller during startup. * **On-board Chargers (OBC):** Managing the connection between the grid and the battery pack. * **Auxiliary Power Systems:** Switching high-voltage DC to DC-DC converters for 12V electronics. --- ### ## Part Number Breakdown (MAH78FAG-R) While manufacturers have specific internal codes, the suffix generally indicates: * **MAH78:** The core series identifier for Fujitsu High Voltage DC relays. * **FAG:** Denotes specific contact material (often silver-tin oxide) and coil sensitivity. * **-R:** Usually indicates **RoHS compliance** or specific packaging (like tray or reel).