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Ensuring Electric Cars Perform Flawlessly
March 13, 2020 Blog

By Hwee-Yng Yeo, Industry Solutions Marketing Manager for Automotive and Energy, Keysight Technologies

 

The electric vehicle market is growing rapidly, and with this growth, there is a seismic shift in design verification and performance testing methodology. Engineers are using new test methods to meet the expanding use of technology within the vehicle, including using emulation methods to reduce cycle time and increase productivity.

But a recent survey by the U.S. National Renewable Energy Laboratory showed that the number one reason people cited for not using an electric vehicle (EV) was cost (51%), closely followed by an inability to charge the EV while away from home (48%).

This  has prompted the e-mobility community to try and bring the costs of electric vehicles down in line with their internal combustion engine (ICE) counterparts.

The use of emulation technology in testing and verification of these designs can go a long way toward containing, if not reducing test costs. It is a positive step towards making EVs more affordable.

 

Car Makers Shift Gears to Meet the Changing Customer

Traditionally carmakers have had long development cycles, compared with other industries.  One reason for this is the need to conform to stringent safety regulations and crash test standards which apply to all brands, be they EV or ICE.  However, new EV brands such as Tesla, unencumbered by the restraints of traditional carmakers, have added pace to developments and played a key role in popularising the electric car.

Last year, Tesla announced the acquisition of Maxell Technologies, a capacitor manufacturer which has pioneered the design of high-power-density ultra-capacitors and new battery technology. Analysts say Tesla aims to use Maxwell’s new dry battery electrode technology to enhance the range of its electric cars beyond 400 miles, with promises of cheaper longer-lasting batteries.

There is no doubt that the internal combustion engine has contributed to pollution, and that, coupled with climate change, has sparked interest in low-to-zero emission alternatives, such as electric cars. As it stands, EVs make up a very small percentage of the total, but that figure is changing and various industry indicators show an impending tipping point. Research has shown that by 2040 EVs are likely to make up 30% of new car sales in China, Europe, India, and the United States. Figure 2 exemplifies the sales projections for EV, ICE and, Other vehicles.

Manufacturers of ICE cars also aim to secure their share of the EV market, and to do so they must tackle the new design and manufacturing challenges EVs pose, wrestling with the complex, high-power, high voltage world of 300 V batteries as drivetrain power sources rather than simply adding horsepower to the traditional ICEs.

In comparison to its petrol or diesel cousin, the EV has numerous specific requirements. The high-energy e-mobility ecosystem requires EV carmakers and electric vehicle supply equipment (EVSE) manufacturers to conform to safety and performance standards, while ensuring compatibility with different models around the world.  Given the complexity of the e-mobility environment, all subsystems must meet performance and mission-critical safety standards.

 

Higher Voltage, Costs, and Risk

The addition of high voltage, high power batteries, is possibly one of the most significant design considerations. Integrating these batteries into onboard systems traditionally powered from a 12 V source is an additional challenge. And there are risks posed by such high voltages.

Equipment used in testing such systems can also be more expensive to buy and run. A 10 KW power source consumes 10 times as much power as a 1 KW source, which, when considering the multiple testbeds used by a carmaker, amounts to quite an expense. Manufacturers need to observe safety standards and ensure that additional equipment such as a power disconnect, is in place.  The heat emitted during the test process is also a consideration. There may be a requirement for additional equipment to help with facilities cooling.

 

Emulating High-Power Onboard Batteries

At the heart of the EV is the battery subsystem.  Energy flows into the battery as it charges, from either the grid or from regenerative braking, and flows from the battery when powering the vehicle or its accessories. The ability of this system to charge and power the vehicle efficiently and safely is pivotal to the functionality of the EV. It is, therefore, important that the battery undergoes rigorous testing to ascertain its functional life and power output. Designers are increasingly turning toward battery emulation to enable performance validation and detection of early failures.

Because an EV is subject to extreme variations in temperature, vibrations, and moisture, these onboard energy subsystems must be able to withstand such environmental conditions. Engineers are therefore using emulation to imitate high power batteries and to study the battery performance impacts on various devices under test (DUTs) in different conditions.

Engineers can also use emulators as DC-DC converters to up-convert 12 V to 48 V to test the behaviour of the battery management circuit, for instance, or to down-convert  48 V to 12 V to test the function of the airconditioner. Engineers are also working on systems whereby excess energy stored in the EV’s battery supplements the grid in peak times. This involves DC-AC conversion, as the grid works on an AC platform. Emulation used to create such an environment allows engineers to validate and test such subsystems.

The Keysight RP7900 is an emulator that can regenerate more than 85% of the power from an EV DUT to the grid, reducing the heat generated in the DUT.

Charging infrastructure is another customer concern. The auto industry is ramping up electronic vehicle supply equipment (EVSE) investments, and the requirements for charging stations could be as high as 30 million units by 2030.  There is massive potential for growth for EVSE makers; however, both EV and EVSE makers must contend with interoperability and conformity regulations across the globe.

Currently charging is divided into 3 levels; AC slow charge – overnight charging from a domestic outlet, which ranges from 220-240 V for Southeast Asia. AC moderate charge – charges a medium-sized EV (24 KWh battery) in 6 hours. DC Fast charge – can charge 80% of a medium-sized EV (24 KWh) battery in as little as 30 minutes. But this high rate of charge could impact on the performance of the battery as it raises its temperature.

Because of the varying voltage standards across the world, carmakers and EVSE manufacturers must ensure their products are interoperable, and meet conformance regulations.

Collaborative efforts between manufacturers of EVs and EVSEs are now creating new, more efficient ways of testing and validating the performance of such interfaces; and emulation technology is an important test method for these.

For example, the man-in-the-middle test, as it is known, uses emulation to measure and decode the communication and power signals between the EVSE and the EV; the tests help to determine potential interoperability issues.  The equipment can be adapted to run different test parameters, depending on the charging point and vehicle models, or a country’s charging standards.

 

Emulation of Battery Cells, Modules and Packs

The cost of the cells used in EVs is another issue facing manufacturers.  Currently, the average energy cost for an EV is about double that of its ICE counterpart. The industry aims to reduce these costs and therefore has teams of specialists at work to bring the energy cost to parity with traditional petrol or diesel automobiles.

New high power energy storage systems and the interconnection of multiple storage cells to form modules and packs, also require intelligent battery management systems (BMS). These systems are responsible for safety, thermal management, power balancing and state of charge.

Emulation, used for testing and optimizing the BMS, can simulate various cell types and a range of battery cell, module and pack models.

As the world gears up towards a future of emission-free transportation, emulation technology will evolve to help engineers realize many e-mobility innovations.

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