EVS26 Developing a Test Procedure to Evaluate Electric Vehicle Supply Equipment and Chargers

This paper describes the processes used and the choices made while developing a procedure to evaluate Electric Vehicle Supply Equipment (EVSE) and Plug-in Electric Vehicle (PEV) chargers and provides some results of the testing process. The procedure defines the battery charging system (i.e., the battery charger, EVSE, battery storage system, auxiliary loads, and vehicle). Each test element is evaluated in terms of function, reliability, safety, quality, cost, efficiency and power quality. The development of a charging system evaluation procedure comes from Southern California Edison’s (SCE) responsibility to ensure safe and reliable function and to minimize system impact. Up to one million PEVs have been projected to be operating in SCE’s service area by 2020. SCE must not only serve these PEVs, but must ensure that they do not have a negative impact on the utility grid. Therefore it is critical that SCE understand the impact of those battery charging systems. SCE also supports the creation of standards to limit wasted energy and negative power quality impacts that these battery charging systems may create. SCE is also using the test procedure to evaluate EVSEs and PEV charging systems for implementation in SCE’s fleet. The results of this procedure are used to give fleet managers the information needed to acquire the most effective and efficient PEV charging equipment. The results will also tell a fleet manager or PEV owner what EVSE would work best with their selected vehicle or vice versa. The procedure provides for the discovery of PEV and EVSE individual and compatibility issues before the PEV is deployed. The final result ensures optimum performance of the PEV system. Through this process, SCE has been able to work with manufacturers of PEVs and EVSEs in order to improve the functionality, robustness, and interoperability of the products.


Background
The importance of this procedure can be overlooked easily when looking at the impact of a single charging system. However, when the individual results are looked at in the light of possibly large numbers of these systems connected to the utility electric grid it shows a different picture. For example, Electric Vehicle Supply Equipment (EVSE) is comparable in impact to recently regulated small battery chargers and power supplies when in no-battery mode. There is growing concern for the energy wasted by inefficient battery chargers and other devices.

Southern California Edison
Southern California Edison has a service area of 50,000 square-miles with five million meters for its customers. SCE's renewable energy portfolio includes approximately 20% of energy from renewable sources, such as wind and solar. SCE operates a fleet of over 6,000 assets to develop and maintain its systems, ranging from powered trailers to Class 8 trucks, and we have demonstrated the largest and most successful PEV fleet with over 20 million electric miles driven. At SCE our number one job is to provide safe and reliable electric service, and the fleet managers make sure that the fleet assets are reliable and effective tools for ensuring that the job gets done. A key part of this process is SCE's Electric Vehicle Technical Center (EVTC).
The EVTC evaluates advanced technology solutions that meet the fleet's missions, optimize energy, and reduce emissions.

Energy Star Program
The Energy Star program [1] was started in 1992 by the EPA in an effort to assist consumers in making energy-wise purchasing decisions. The Energy Star program is a voluntary labelling program that began with just a few electronic products, and has since expanded to include major appliances, lighting, office equipment, home electronics, residential heating and cooling, and even new homes and commercial and industrial buildings. The most recent additions included small power supplies and small consumer appliance battery charger systems. This program, however, does not comprehensively address larger battery chargers or vehicles, and does not address EVSEs at all.

California Energy Commission
According to a Frequently Asked Questions (FAQ) sheet published by the California Energy Commission (CEC) in January 2012 [2], as of 2009 there were approximately 170 million battery chargers in California households. Per the graph published in the same FAQ sheet, battery chargers in California currently consume approximately 7,700 GWh/year. Without any standards imposed on battery chargers, this number is expected to almost double over the next 10 years. The CEC has enacted standards to require a certain level of efficiency from the covered battery charger systems (not including on-road vehicles). The standards apply to active charging mode, maintenance mode, and "no-battery" mode, when no-battery is connected to the charger. They divide battery chargers into two main groups: small and large, with large battery chargers having an input rating of grater then 2 kW. The CEC estimates that the new standards could generate a savings of 2,200 GWh per year in California, for an electrical cost savings of $306 million per year.

Scope
The first step in developing the procedure was to identify the scope and test system boundary. The scope of the procedure is to evaluate Electric Vehicle Supply Equipment (EVSE) and Plug-in Electric Vehicle (PEV) battery charging systems in terms of function, reliability, safety, quality, cost, efficiency, and power quality. It is also important to define specifically what is measured and how, and this is depicted with the system boundary. The boundary of the system under test is shown in Figure 1. The figure shows an on-board charger, however an off-board charger would be tested in the same way except that the charger and EVSE would be one block and would be in the place of the EVSE box. Data is collected at the various monitoring points based on the specific test being performed.

Test Criteria
The next step was to identify the aspects of the researched codes and standards that applied within our defined system boundary and the scope of the evaluation goals. SCE devised several groups of tests incorporating safety, functionality, grid events, power quality, and ergonomics. For each of these categories a number of tests were created. The Nationally Recognized Testing Laboratories (NRTL) perform safety and function testing on commercial products. There was not a need to duplicate all of the testing that had been performed by them.
Some testing was designated to be important enough that a similar test was developed to be performed at SCE; these were mostly tests that involved safety. Once the tests were designated, specific procedures were developed for each using the specific parameters identified in the researched codes and standards.

Designing Tests
After the specific aspects of each test were selected, acceptable limits were determined from the researched materials. Test procedures were created and revised. Data sheets were created to record the results of the tests. Good data sheets are vital to an effective procedure, as they guide the test technician through the process of properly executing the procedure. For each procedure the steps were determined with the specific results expected and safety of the technician in mind. After the procedure was initially completed an initial test was performed to review and validate the procedure and to discover any errors or areas for improvement.

Review
The individual procedures for each attribute were combined and organized into a cohesive test procedure. The completed procedure was then reviewed with engineers and managers. A few tests were added after the initial completion of the procedure. It was determined by SCE engineers that certain aspects of the charging system were not being fully represented by the current results. This model of continuous improvement is a key aspect of SCE. After the procedure was reviewed and approved, SCE began using it for testing.

Executing the Procedures
SCE began using the procedure for testing with six EVSEs, one off-board charger, and seven vehicles. The PEVs and EVSEs used the SAE J1772 connector and the off-board charger used the CHAdeMO DC connector. The components were tested individually and in various combinations. The procedure includes testing of both individual components and whole systems since the results would be affected if one component of a system were changed. As the testing progressed through the various EVSEs and PEVs, it was found that one test or another could not be performed as it was written either because of the EVSEs' design or the directions of the test. The specific test was then reviewed and possibly revised to improve the test's All of the grid tests except for the long duration outage do not use a vehicle for the tests, but rather, use a device called a grid simulator. One test, the momentary outage test, applies a short power loss. Charging systems should be able to recover unaided from such events. Two units failed the momentary outage test because they required user intervention to restart the charge. All EVSEs passed the other grid event tests, and were able to start a charge after each of the tests performed.
The insertion and removal force test showed all of the EVSE connectors' force effort levels to be within acceptable limits. Figure 3 shows the results of the force test. Unit 5 used a different connector manufacturer then the others and showed a higher required force. As a part of the testing the no-battery mode, sometimes called "idle" or "stand-by" mode, energy consumption was measured for each unit. Figure 4 shows the results of the one-hour nobattery mode energy consumption test. The results varied widely with the features included with each system (such as displays), from 2 W up to 14 W. This wide variation points toward the need for a standard for energy consumption in these devices when they are in no-battery mode.