6 Common Reasons Products Fail EMC Tests and How to Fix Them
The points where electronic products most often fail EMC certification, and simple measures you can take at the design stage, from an engineer's view.
3 min readOctober 19, 2026
Why Is a Charger a Demanding Product?
Chargers convert tens or even hundreds of kilowatts with high-frequency power electronics. The switching noise generated in this conversion travels both to the grid side and onto the vehicle cable.
At the same time, chargers operate close to radio transmitters and other electrical equipment, in car parks and along roads. Both the noise they emit and their immunity to outside disturbances are critical.
Which Standards Apply?
In Europe, EMC requirements for chargers are defined by IEC 61851-21-2. This standard sets emission and immunity tests according to the charger's environment and power. On-board chargers on the vehicle side are assessed under automotive standards such as CISPR 25.
Tests must be run with the charger under real load, charging a vehicle or vehicle simulator. The noise of an idling charger doesn't reflect its behavior at full power.
Challenges of High-Power Testing
Running a high-power charger in a test chamber requires a strong, filtered power entry into the room, a battery simulator to absorb the load and cooling for equipment that heats up. All these components must be integrated without compromising the room's shielding.
Load equipment is usually kept outside the chamber, with power brought in through high-current filters. Filters are selected by both current rating and leakage current limits.
The Right Chamber Size
Wall-mounted chargers can be tested in a compact semi-anechoic chamber, while floor-standing fast chargers and tests with a vehicle require large chambers such as a SAC-10.
By reviewing your product range and test plan together, we define the chamber size, power entry and filter capacity. You'll find EV-focused options in our automotive sector solutions.
Frequently Asked Questions
How much power input does charger testing need?
It's set by the highest-power charger to be tested. Filter and cable sizes are chosen to match.
Can testing be done without a vehicle?
Yes. With a vehicle simulator or battery emulator, the charger can run under real load.
Can an existing EMC chamber be adapted for charger tests?
Often yes, by increasing the power entry and filter capacity; the existing infrastructure is inspected during the survey.
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