Tag: battery emulator

Electric Vehicle Market Drivers & Testing Requirements

Electric Vehicle Transportation - NH Research (NHR)

EV Batteries & Powertrains Increase in Power Levels

As the electric vehicle (EV) industry continues to accelerate, automotive engineers must address new testing challenges for designing higher performance batteries, electric powertrain systems, power electronic components and DC fast chargers. Power levels are increasing across e-mobility markets such as passenger electric vehicles, heavy duty electric trucks, and electric fleets. These market trends require test solutions that can test today’s technologies and tomorrow’s innovations.

Power and voltage levels are transitioning from a traditional 300/400VDC level toward 800/1000VDC. Higher voltages permit faster charging and increase power transfer while reducing vehicle weight. For example, in 2019 most available BEVs were similar to Tesla’s Model 3 and GM’s Chevy Bolt, with a nominal voltage of ~350VDC, whereas Porsche announced the Taycan architecture utilizing a higher 800VDC battery system. This higher voltage allows nearly three times (3x) the additional power to be transferred for the same wire size. Porsche demonstrated this with an IONITY system charging at 350kW, which is nearly 3x the 120kW available through other “fast” supercharging networks.

It is expected that both 800V and 350V vehicles will charge at an electric-only refueling station the same way gasoline and diesel cars do today. Engineers should keep this dual-voltage reality in mind when specifying the power requirements because many of the high-power test systems are only designed for a single range. Selecting a system that can provide both traditional and high-voltage levels ensures that the right equipment is available to meet current and future needs. It is equally important that a battery emulation system reacts with a quick voltage response to changes in current or power draw in order to accurately simulate the electrical storage system (battery).

Auto manufacturers have dramatically increased the relative capacity of the battery packs in their vehicles to reduce “range anxiety”. For example, the 2019 Nissan Leaf has a 50% larger battery compared to older 40kW models, and Tesla’s Model S offers a 100kW battery, that is 66% larger than the original standard-sized battery. Battery capacity and battery performance are always improving, suggesting that engineers must consider flexibility and programmability in selecting a battery test or battery emulation solution.

EV Testing Requires Modular, Scalable Test Solutions

NHR Provides Modular, High Voltage Bi-Directional Power up to 2.4 MW

NHR’s ev test equipment is designed for fully independent operation and can be paralleled, increasing the maximum power and current capability to the level required. This modular expansion through paralleling ensures that you can start testing to today’s application levels, knowing that additional power is available if needed in the future. Higher-power models provide dual ranges, allowing the equipment to test and emulate today’s batteries and provide the right tool that can scale to address increases in battery voltage and power.

The 9300 High Voltage Battery Test System has a dual power range that covers both lower (up to 600 V) and higher power (up to 1200 V) applications using a single product. This modular system can be scaled up to 2.4 MW in 100 kW building blocks, offering a wide operating envelope. With NHR’s battery emulation mode, customers are able to simulate a wide range of battery power levels without having to change test equipment. Alternatively, the 9200 Battery Test System has a multi-channel capability with the possibility to mix and match voltage and current levels at lower power ranges. This battery cycler and battery emulator is expandable in 12kW block sizes and has voltage options from 40V to 600VDC. This series uses the same drivers, touch panel controls, and software options, making NHR your ideal solution partner for both high-power and low-power EV architectures.

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How is a Battery Emulator Different from Power Supplies & Electronic Loads?

Battery Emulator vs. Power Supplies and Loads - NH Research (NHR)

Battery Emulators VS. Power Supplies & Electronic Loads

Battery emulators are bi-directional, whereas power supplies and loads are unidirectional devices. A power supply regulates voltage and expects some amount of current to be drawn. Electronic loads regulate current and expect voltage to be provided. Being uni-directional, these devices are unable to accept or supply power in the reverse direction.

An approach engineers often take is to build their own test setup using sources and loads. This can be challenging, and time consuming, and has many of the disadvantages of the common DC bus architecture described above. Typically, DC sources have a programmed response time of 10 to 100 ms, which is far too slow for today’s EV applications such as electric powertrains. For example, using a DC load to modulate power or provide a return path for back-EMF requires complicated software development, considerable integration and test time, and does not provide an accurate simulation of the battery’s internal resistance. Additionally, the load must consume power at all times, and since it is not regenerative, all of the power is dissipated as heat waste, increasing operating costs and creating uncomfortable work conditions.

Battery emulators maintain a positive DC voltage and can immediately accept or deliver current, allowing power to flow in either direction. More advanced battery emulators, like NHR’s 9300 Battery Emulator, allow further real- world simulation of battery characteristics by modeling the battery packs series-resistance (RINT).

The RINT Model: Accurately Simulating Battery Characteristics

The Internal Resistance (RINT) model provides a simulation of the battery’s internal chemical resistance, along with additional pack resistances created by internal connections, contactors, and safety components. The RINT model can be implemented with a true bi-directional source (Vocv) and a programmable series-resistance (Rs). This model is sufficient for understanding the major characteristics of battery-based resistances and pack resistances. While the number of mathematical models has increased, these more complicated models are used to understand the electro-chemical characteristics of batteries, the nuances of  which have little impact on the overall system when compared with the total resistance of the pack.

NHR’s battery emulators feature this equivalent RINT Model providing an electronically programmable “Battery Emulation” mode. As in a real battery, NHR’s battery emulators adjust the output voltage depending on the direction and amplitude of current flow.  This automatic adjustment of output voltage better simulates real-world battery pack characteristics especially when compared with common DC-bus and source/load simulation systems.

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Battery emulation is ideal for applications such as electric powertrain, fuel cell emulation, energy storage systems emulation, Solar PV inverter testing, DC Bus emulation, and more. For more information about key differentiators and technology considerations for battery emulation, please contact us.

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Testing Electric Vehicles Using Battery Emulation

Testing Electric Vehicles with Battery Emulation - NH Research (NHR)

Today, next generation battery emulation provides a competitive advantage for testing electric vehicle (EV) components and systems. Battery Emulation is ideal for testing the electric powertrain, DC fast charging and other EV applications in which a battery is required for testing.

Using batteries as power sources for testing is an extremely time-consuming and costly challenge across the transportation electrification industry including EV, aerospace, and e-mobility markets. The transition from traditional to modern electrification architectures, require flexible and scalable testing methodologies. Testing with batteries can delay projects, increase safety risks and hinder engineering productivity. As electrification is evolving to higher power demands, the ability to emulate a battery or energy storage systems with speed and accuracy is critical. Battery emulation can substantially reduce test time, energy consumption and operating costs.

Battery Emulation Testing vs. Real Battery Testing

There are 3 key benefits to testing electric vehicles with battery emulation or battery simulator testing, rather than using a real battery. Battery emulation dramatically reduces testing time, provides highly repeatable test results, and creates a safer test environment. This results in preparation time, operator errors, and result variations due to battery temperature or aging, being eliminated.

Testing EVs with Battery Emulation Reduces Testing Time

Testing a real battery often requires operator preparation for each step. Batteries must first be charged, or discharged, then allowed to rest, and finally tested. The significant battery preparation time can be avoided by using an emulated battery. Emulation can reduce total test times by more than 70%.

Battery Emulation Provides Repeatable Test Results

Over time, batteries provide inconsistent test results, wear out, and need to be replaced. Battery age, internal temperature, and cycling are all contributing factors to the limited battery life-span. Manual battery operation, including rest time facilitation, can also cause inaccurate test results. Battery emulation provides consistent and repeatable test results, unlike those from real battery testing, during which battery changes and operator errors cause variations in test results.

Battery Emulation Improves Safety

Although batteries are generally safe when operated within normal operating ranges, they are high energy devices that may pose serious risks upon battery or unit under test (UUT) failure. Such risks include exposure to dangerous gases, fires, explosions, or corrosive chemicals. These concerns have led to safety policies stating that tests must be conducted and monitored during working hours. Furthermore, testing extreme cases of over-discharged or over-charged batteries can pose unpredictable risks and safety hazards. Battery emulation creates a safe testing environment without any of the concerns that arise when real batteries are used. Also, emulation safely verifies UUT behavior when a battery is outside a normal operating condition.

Not all Battery Emulators are Created Equal

While testing with real batteries is possible, it can seem quite impractical. Using battery emulator or battery simulator testing produces test results faster, provides a consistent test, and can safely test power electronic devices that typically require a real battery.

However, not all battery emulators, regenerative DC sources and DC common bus architectures are optimally designed to provide accurate and timely results. There are key technology considerations when selecting a battery emulator for your application. Contact us to learn what battery emulation capabilities are the right approaches for faster, scalable and more repeatable testing.

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