DC Charging Station Relay Company: 48V 150A Latching Relay Sourcing Guide

Close the door on a 120 kW DC charging cabinet and the part most likely to be re-specified in year three is not the power module. It is the 48 VDC, 150 A latching relay that switches the low-voltage DC distribution path inside the cabinet, a component expected to survive roughly 21,000 operating events if the site averages six sessions a day across a ten-year service life. Three variables decide whether a supplier can support that duty: arc behaviour at the contact gap, contact resistance stability at rated current, and documentation an engineer can actually check.

What a DC charging station relay does that an AC PDU relay does not

A DC charging station relay interrupts direct current, so the arc never reaches the natural zero crossing that lets an AC contact clear itself. On a 50 Hz AC circuit the current passes through zero every 10 milliseconds and the arc extinguishes unassisted; on a DC circuit the arc keeps conducting until the contact gap and the arc control geometry stretch it far enough to cool.

At 48 VDC the arc is short, but it is not absent. At 150 A the contact still has to absorb stored inductive energy from cabinet cabling and the capacitor bank behind it, and contact material selection matters more than the headline current figure suggests.

Read the AC and DC families as a pair rather than as substitutes. The 250 VAC models are described as latching relays for the PDU, while the 48 VDC model moves to a 150 A rating on a DC contact system. The wider EV charging station relay range splits along exactly that line, and a cabinet that mixes AC output distribution with a low-voltage DC bus needs both halves of it.

Three numbers decide fitment before brand does

Contact current, contact resistance and coil voltage decide fitment before brand does, and of the three, contact resistance is the one that shows up in the thermal test rather than in the datasheet headline.

Every 0.1 milliohm of contact resistance dissipates 2.25 W at 150 A, because power equals current squared multiplied by resistance. A supplier declaring 0.5 milliohm maximum is describing 11.25 W of heat inside a sealed capsule before you add terminal and busbar losses; one declaring 1.0 milliohm is describing 22.5 W. Convert the declared maximum before you compare quotes, and ignore typical values entirely.

Coil voltage is the second screen. A 48 VDC coil has to pull in at the bottom of the auxiliary supply tolerance band, not at nominal, and it has to release cleanly when the driver drops the pulse. That behaviour is a tested window, not a line on a label.

• Ask for pull-in and drop-out voltage windows across the full operating temperature range, not a single nominal figure.
• Ask for maximum contact resistance together with the measurement method and the test current used.
• Ask for the endurance curve at your actual load rather than at a reduced resistive load that flatters the contact.

Standards evidence to request before a sample ships

Three document sets should be on your desk before a sample ships: an IEC 61810-1 endurance report at your rated load, a cabinet-level standard reference for the charging system, and an ISO 9001:2015 certificate whose scope names the relay family and model numbers.

Sequence the request so it cannot be answered with a brochure. Send the load profile first, then ask for the endurance report against it, then ask for the certificate scope page, then lock the change notification commitment. Each step produces a document you can file.

What factory data predicts about delivery risk

Annual volume, in-house assembly depth and engineering headcount predict delivery risk better than a price list, because in latching relays capacity decides whether a custom coil or a new contact material can be scheduled without moving your date.

Huajin Technology Jiaxing Co., Ltd. shows how to read those numbers. The company was registered in May 2021 with RMB 10 million in capital, runs an 8,000 square meter plant on Yanyu Road in Yucheng, Haiyan County, Jiaxing, Zhejiang, and employs more than 120 people. It states capacity above 10 million magnetic latching relays per year with roughly 30% of output exported, and lists 8 senior R and D engineers supported by a municipal level high-tech research centre. Quality documentation covers ISO 9001:2015, CCC, State Grid and TUV certification.

• Capacity quoted in units per year, never in undefined sets
• Export share read as documentation and packaging maturity
• R and D headcount read as custom coil and tooling capability
• Certification scope read as model level coverage, not brand level

Platform reuse is the detail worth checking in any catalogue. The same HJE11B60A250VAC model appears under overvoltage, undervoltage and three-phase intelligent capacitor headings, and HJE31B100A appears under both DIN rail meter and multi-circuit headings. That is efficient engineering, one tooling set serving several device families, and it also means a contact material change made for a meter customer can land in the charging relay you are buying.

HJE12A-150A-48VDC Latching Relay for DC Charging150A/48VDC latching relay with double contacts, magnetic blowout and auxiliary status switch; its shared platform makes contact-material change control worth checking.View Product →

HJE11F-120A-250VAC Magnetic Latching Relay for PCB PDUs120A/250VAC PCB-mount magnetic latching relay with low coil power and 4kV isolation; platform reuse makes contact-material and change-control checks relevant.View Product →

A five criteria scorecard for DC charging station relay companies

Score five weighted criteria before you score price: DC load endurance at 30%, coil tolerance at 20%, change control at 20%, capacity and lead time at 15%, and certification scope at 15%.

The weighting is deliberate. Endurance carries the largest share because a DC contact failure is a field return with a truck roll attached, while a coil mismatch usually surfaces on the bench during the first power-up. Anything that cannot be evidenced in writing scores zero rather than a partial mark.

From sample request to serial release in four gates

A 48 VDC, 150 A latching relay normally clears four gates in about fourteen weeks: sample selection, design validation, pilot run and serial release.

If the coil voltage, footprint or termination has to change, confirm the custom route early, because customized relay solutions usually add tooling lead time to gates three and four rather than to the sample stage.

Questions that come up in DC charging relay sourcing

Which contact voltage should a DC charging cabinet specify for its relay?

48 VDC is the correct rating for low-voltage DC distribution and auxiliary paths inside the cabinet, which is the duty the HJE12A150A48VDC is built for; 250 VAC applies to the AC PDU side. Neither rating covers the 200 VDC to 1,000 VDC main charging output, which belongs to a different device class entirely.

How many samples are enough before approving a latching relay?

Take 10 to 20 pieces from at least two production lots and run 2,000 operations at rated load on each, logging contact resistance every 500 cycles. Flag any unit whose final reading exceeds 1.5 times its own initial reading, because that pattern points to contact material or plating rather than to application error.

Does a relay company's export share prove build quality?

No. A 30% export share shows the supplier is set up for export packing, labelling and certificate translation. Build quality is proved by endurance data at 48 VDC and the rated current, plus a certificate whose scope lists the exact model number being ordered.

What should a purchase order say about product change notification?

Require written notice at least 90 days before any change to contact material, plating, coil wire, magnet grade or housing tooling, with a right to re-qualify and to reject stock built to the changed design. That clause is what makes a ten-year service commitment enforceable.