Testing EV charging points

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As more EVs take to the roads, pressures on the available charging network are growing. Investment in charging networks has seen the free installation of residential charging points being followed by an initial concentration of public EVSEs (electric vehicle supply equipment).

The most common type of EVSE installation provides ‘slow charging’ to the vehicle as an AC supply over periods from 4-12 hours for a full charge, depending on the rating of the supply. Rapid charging DC systems have also become available.

Although different modes or levels of charging have different definitions around the world, the operation and functionality of electric vehicle supple equipment is controlled by official product standards. The international standard IEC 61851 defines the requirements for charging equipment and also covers aspects such as the protocol used for communication between the vehicle and charging point. In the USA, the SAE J1772 standard is a close equivalent of IEC 61851. Compliance with one or other of these standards is mandatory to ensure the safe operation and reliable performance of the EVSE installations.

In general terms, the standards describe the characteristics and operational conditions of the charging station and its connection to the EV, the electrical safety of operators and third parties, and the characteristics to be complied with by the vehicle with respect to the power supplied when the vehicle is earthed.

For the user of an EVSE, recharging the vehicle should be as simple as connecting a normal electrical appliance to the electricity supply. However, to ensure that this operation takes place in complete safety, the charging station must perform several system safety checks. To do this, direct communication between the vehicle and the station is established when the connection is made.

In order to avoid accidental contact with live parts (for example, the terminals on the charging cable), the EVSE charging output cannot be energized unless an EV is connected; for instance, there cannot be power on the EVSE output connector or cable unless the cable is plugged into an EV and communication between the two is established.

Herein lies a fundamental problem: operational performance and diagnosis of any EVSE system faults cannot be determined unless an EV is connected to the charging system and signal communication is established between the two parts of the system.

As a result, several of the tests defined by electrical installation standards such as IEC 60364 and the National Electric Code, such as earth loop impedance and RCD testing, cannot be carried out unless the circuit under test is energized. Functional testing of the installation also requires the EVSE to be energized.

One means of checking the functionality would be to attempt to charge an EV immediately after each and every EVSE installation but it would be impractical and extremely time consuming to do so. It should also be noted that this would not provide any information on how the EVSE would respond if there is a fault with the EV or the charging cable.

Of course the fundamental requirement underlying this commitment is that the capability of the EVSE network remains robust and reliable in meeting the recharging needs of the vehicle whenever required.

Seaward has introduced a new testing and diagnostic device to allow EVSE installers to demonstrate that the charging equipment is both safe and operating in accordance with the same specification as when it was installed. The Seaward EV100 has been designed to verify EVSE safety and operation by simulating the presence of an EV. Direct communications between the tester and the EVSE is established via a standard charging cable or through direct connection to the EVSE output terminal. This enables the instrument to control the EVSE and sequence through a number of test conditions to enable all appropriate electrical tests to be carried out.

The EV100 will also simulate a number of vehicle faults and measure the EVSE response. Test results are stored in an internal memory and can be transferred to a smartphone app using wireless communications.

As well as carrying out basic field tests, more detailed diagnostic data from the charge point is retained in the tester and can be transferred to the EVSEMobile Android app using NFC wireless communications. The EVSEMobile app enables advanced data to be viewed, test certificates to be produced and test data to be exported as a csv file and emailed back to the office. Comprehensive technical test data can therefore be assessed by an office-based diagnostics engineer with remedial instructions being provided to the technician working in the field.

September 17, 2015

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