Complete Relay for Charging Station: AC and DC Latching Relay Specs, Selection Guide

Charging stations are power-dense environments where every switching element has to work flawlessly for years. A single contact failure inside a DC fast-charge cabinet can take an entire charging gun offline, while the lost revenue per idle charging spot can exceed hundreds of euros per day. For charging pile manufacturers, the relay for charging station is not a generic BOM item; it is a reliability decision that directly determines field return rates and operator uptime. Huajin Technology Jiaxing Co., Ltd. designs magnetic latching relays specifically for AC and DC charging PDU circuits, with current ratings up to 150A and voltage classes from 48VDC to 250VAC. The company has been producing latching relays for charging pile and metering applications since 2021, with over 100 engineers and a 10-million-unit annual production capacity.

HJE11F-120A-250VAC Latching Relay for PDUProduct Overview: Designed specifically for high-density power distribution units (PDUs), this high-power control core is directly integrated into the PCB board. With ...View Product →

Relay for Charging Station: How the Latching Principle Works

The latching relay in a charging station is a bistable switch. It changes state with a short pulse and holds that state indefinitely without power. This is why charging pile manufacturers specify latching relays instead of standard electromagnetic relays. In a typical charging station PDU, the relay is the primary switching element between the charging controller and the power output stage.

Pulse Coil and Permanent Magnet Holding

At its core, the latching relay has two states: open and closed. The control board sends a current pulse through the coil. The coil generates a magnetic field that moves the armature, closing or opening the contacts. Permanent magnets then hold the armature in that position. The pulse duration is typically 20-80ms, which is enough to overcome the spring return force.

1. The charging controller sends a 20-80ms pulse to the relay coil
2. The armature moves and the contact set changes state
3. Permanent magnets hold the armature in its new position
4. The pulse is removed and the relay holds its state with zero holding power

What This Means for Charging Station Design

Because the relay does not need continuous current to stay in a given state, the heat load inside a sealed PDU cabinet is significantly lower. This extends the life of adjacent components and reduces the risk of insulation degradation. For AC and DC charging station builders, this translates into fewer field failures and better charging availability. On a per-relay basis, minimizing holding power also improves the overall energy efficiency of the charging station during standby intervals.

AC vs DC Charging Station Relay: Rating and Selection Differences

The relay for charging station must match the bus architecture of the charging pile. AC charging stations route 250VAC through a PDU, while DC fast-charging stations control a 48VDC bus at higher currents. The two are not interchangeable, and using the wrong voltage class is a safety risk as well as a reliability problem.

HJE12A-150A-48VDC Latching Relay for DC chargingProduct Definition: The HJE12A-150A-48VDC is a high-performance DC relay designed specifically for 48VDC voltage systems, with a maximum current carrying capacity of 1...View Product →

AC Charging PDU Control

In AC charging stations, the latching relay sits inside the power distribution unit. It receives control signals from the charging controller and switches the 250VAC branch circuit. The HJE11F120A250VAC is a common choice for this application, with 120A rating and UC3 compliance. The relay must handle the inrush current of the charging gun's internal electronics without contact welding.

DC Fast-Charging Contactor Logic

DC fast-charging stations operate on a 48VDC bus. The relay must handle high DC currents, which create different arc extinction demands than AC loads. DC switching produces a sustained arc that can erode contacts if the relay is not properly rated. The HJE12A150A48VDC is designed for this exact condition, providing 150A switching capacity at 48VDC. The contact gap and magnet design are optimized to break DC arcs reliably.

How to Choose a Relay for Charging Station: Specification Checklist

Selecting the relay for charging station is not a matter of matching the highest current rating. The actual load type, ambient temperature, inrush profile, and switching frequency all affect contact life. These are the specifications that matter when checking a relay against a charging station design.

HJE12A-120A-250VAC Latching Relay for PDUThe Powerful Core of the PDU!View Product →

Current and Voltage Compatibility

The relay must match the bus voltage first. For AC charging PDU circuits, 250VAC is the standard. For DC charging stations, 48VDC is the common intermediate bus. The current rating should accommodate the maximum load plus a margin, but not overload the contact set. A 120A relay on a 100A load has more contact life margin than a 120A relay running at its absolute limit.

Standard Compliance: UC2, UC3 and State Grid

China's State Grid has issued multiple editions of metering and protection relay standards. UC2 and UC3 represent different compliance levels, while the 25th Edition of the State Grid standard defines specific performance requirements for distribution equipment relays. A relay with the right standard compliance eases certification work for the charging station manufacturer. For export markets, TUV and ISO9001-2015 certifications are also important signals of quality consistency.

Product Variants and Mounting Forms

Charging station relays come in different package formats. Some are designed for PCB mounting, others for DIN rail. The HJE11F120A250VAC and HJE12A120A250VAC offer different mounting configurations, allowing charging pile designers to choose the package that fits their PDU layout. Split-type and integrated variants are also available where the relay is paired with a shunt or current transformer.

Reliability and Certification: Factory Quality Governs Charging Station Uptime

A relay that fails inside a charging station costs far more than the relay itself. The repair cost, the downtime, and the loss of service revenue can add up quickly. Certification is a starting point, but production discipline is the real differentiator.

Certified relays also reduce the risk of contact welding and switching failures, which are among the core charging station safety benefits that operators depend on. In a charging station, a welded relay contact can cause a short circuit or an uncontrolled current flow, which is why the switching element needs to be qualified for the actual load profile.

• ISO9001-2015 quality management system certification
• CCC certification for the China market
• State Grid certification for distribution equipment suppliers
• TUV certification for European and international markets

Charging Station Relay FAQ