The Effects of Electric Vehicle Charging Stations on Vehicle On-Board Cables: Potential Damage Mechanisms and Preventive Approaches

1. Introduction

At the heart of energy conversion in electric vehicles, the On-Board Charger (OBC) converts AC current from the grid to a suitable DC level for the battery. During this conversion process, the OBC is a sensitive component to quality degradation from both grid and charging station sources. In particular, substandard stations can cause problems such as thermal stress, semiconductor degradation, and communication interruptions in OBC circuits.

2. OBC Operating Principle

An OBC typically consists of the following sub-components: Input filter, EMI suppression circuit, PFC (Power Factor Correction) stage, DC/DC converter, isolation, and communication interfaces (CP, PP, PLC). The OBC operates in accordance with IEC 61851-1 and ISO 15118 standards, ensuring both charging safety and energy quality. However, interaction with systems outside these standards can disrupt the thermal and electrical stability of the OBC.

3. OBC Damage Mechanisms Caused by Charging Stations

3.1. Voltage Imbalances and Peaks — When the phase-to-phase voltage difference in three-phase charging stations exceeds 10 V, an asymmetric current draw occurs at the input of the OBC. This leads to MOSFET/IGBT overheating in the PFC circuit and reduces capacitor life.

3.2. Harmonic Distortions and EMC Noise — Charging units that do not comply with the IEC 61000-3-2 standard produce high-frequency harmonics. These harmonics can interfere with the reference signals on the OBC control board, causing false triggering and low efficiency.

3.3. Grounding and Insulation Problems — Weak or faulty grounding creates a potential difference between the vehicle body and the station. This difference can cause the insulation monitoring system to continuously generate errors and interrupt the charging process.

3.4. Communication Errors (CP/PP/PLC) — Synchronization errors in OCPP or ISO 15118 protocols destabilize the current limiting and interruption loops. This situation shortens the lifespan of the OBC relay and can even cause software resets.

4. Experimental and Field Observations

The literature reports that OBC failures are more frequent, especially in low-quality AC stations. For example: in sockets with weak contacts, the OBC input current fluctuates due to heat increase; in incorrect phase sequences, the OBC enters sudden start-stop cycles; and when the CP signal is unstable, the software watchdog is triggered.

5. Protection and Prevention Methods

Charging Station Side: IEC 61851-1 compliant phase sequence control and insulation measurement, type-2 sockets equipped with temperature sensors, EMI filters that suppress voltage peaks, instantaneous fault reporting infrastructure with OCPP 2.0.1.

OBC Side: Input protection circuits with MOV, NTC, and TVS combinations, adaptive PFC control algorithms, communication noise filtering software, automatic current reduction modes at high temperatures.

6. Conclusion

OBC units are one of the most complex and expensive electronic components in electric vehicles. Therefore, charging station quality directly determines the lifespan of the OBC. Stations that do not meet standards increase the risk of failure in the short term and performance loss in the long term. For the OBC and charging infrastructure to work together harmoniously, both manufacturers and operators must make IEC and ISO standards mandatory testing criteria.

Resources

[1]IEC 61851-1: Electric Vehicle Conductive Charging System – Part 1: GeneralRequirements.

[2]ISO 15118-2: Road Vehicles – Vehicle to Grid Communication Interface.

[3]SAE J2894-1: Power Quality Requirements for Plug-in Electric Vehicle Chargers.

[4]TSE EN 62196-2: Plugs, Socket-Outlets, Vehicle Connectors and Vehicle Inlets – Conductive Charging.

[5]IEC 61000-4-5: Surge Immunity Test.

1.What is OBC (On-Board Charger)?

OBC is a power converter integrated into the vehicle.

• Receives AC energy from the mains

• Isolates

• Regulates

• Converts to DC charging current suitable for the battery

In AC charging (Type-2), all power conversion takes place within the OBC. In DC fast charging, the OBC is disabled.

2. Typical OBC Electronic Block Diagram

The following structure is common to almost all EVs:

3. Layer-by-Layer Operation Logic Let's see how the system works step by step: AC Input + EMI Filter Energy from the mains: • 230V (single phase) • 400V (3 phase)

A filter is used at this point:

• Reduces electromagnetic noise

• Ensures vehicle-mains compatibility (CISPR, IEC standards)

AC → DC Rectifier

Typically:

• Diode bridge

• Active rectifier (SiC MOSFET)

Here, energy becomes a DC bus:

• ~325V DC (single phase)

• ~700V DC (3 phase)

PFC (Power Factor Correction)

This section is the most critical part of the OBC.

Purpose:

• To draw a smooth sine current from the grid

• To avoid harmonic generation

• To bring the power factor closer to 0.99

Topology:

• Boost PFC

DC Link (Bus Stop)

This section contains large capacitors:

• Balances voltage fluctuations

• Acts as an energy buffer

Isolated DC-DC Converter

This is the heart of the OBC.

Purpose:

• Isolation between battery and mains

• Regulating voltage to match battery level

Topologies:

• LLC Resonant Converter (most common)

• Phase Shift Full Bridge

Must include:

• High-frequency transformer

• Galvanic isolation

Output Rectifier + Filter

DC output is made smooth:

• Ripple is reduced

• Battery is charged safely

Battery Management (Communication with BMS)

The OBC does not "charge" the battery directly; it charges only if the BMS allows it.

Via CAN communication:

• Maximum voltage

• Maximum current

• Cell temperature

• SOC level

are monitored. 4. OBC Control System (Electronic Brain)

The following control structures are always included in the OBC:

Sensors

• AC input current

• DC bus voltage

• Output current

• Transformer temperature

• Insulation resistance

Controller

• DSP or MCU (TI C2000, NXP, etc.)

PWM Drivers

• MOSFET / IGBT / SiC Gate Driver

5. Power Levels