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Test Solutions for Advanced HEV/EV Battery Management Systems

The number of semiconductors used in electric vehicles is growing rapidly as each Electronic control unit (ECU) requires large amounts of silicon to perform its duties. In order for automakers to significantly reduce the bill of materials (BOM) and save money by purchasing fewer silicon devices, TI’s goal is to manufacture highly integrated semiconductor devices.

In a pilot project, Comemso and Texas Instruments (TI) demonstrated how to use the comemso BMS test system to fully create and evaluate a battery management system (BMS) based on a Texas Instruments development platform. The new graphical interface enables developers to operate a single view of all aspects of TI’s electric vehicle (EV) BMS development platform and comemso BMS test platform with battery emulation.

BMS is an essential part of EV to monitor and measure the battery, including battery health and state of charge, to increase the EV’s cruising range. BMS designs are complex and vary from manufacturer to manufacturer; therefore, BMS development and testing must be simplified to accelerate time to market.

In an exclusive interview with Power Electronics News, Mark Ng, general manager of TI HEV/EV power systems, emphasized that the cooperation with comemso shows TI’s commitment to its customers, which means that TI not only sells a single IC, but also ensures that the sale is complete and verified s solution.

“Texas Instruments is developing a complete portfolio of semiconductor devices for automotive BMS. Automotive OEMs and suppliers use our equipment to develop high-voltage battery packs for pure electric vehicles, which can be 400V or 800V. We recently created a complete BMS reference platform to showcase our flagship silicon device, and we used the comemso hardware-in-the-loop (HIL) simulator to test and verify the overall functionality of the entire system.Since the BMS is an already complex system, design engineers are happy to have a comprehensive Tested and validated system solutions. This helps them improve design cycles and minimize time-to-market,” said Mark Ng.

Here comes the hardware-in-the-loop (HIL) simulation capability. HIL simulation develops and tests complex real-time embedded systems such as BMS. Connecting embedded systems to real hardware is often the best development method. The EV industry uses HIL simulators to simulate the cost, duration, safety and availability of high voltage batteries. The comemso HIL simulator can electrically simulate all cell voltages and pack currents, making it a useful test platform. A factory model set up for the target battery chemistry controls the voltage output of each electrically simulated battery. It can be dangerous, expensive or impractical to evaluate algorithms and hardware before connecting the device to a live battery.

building management system

According to Mark Ng, the comemso system allows us to:

• Provides individual cell voltage and temperature for our BQ79718-Q1 battery monitor
• Provides battery pack current (via shunt emulation) for our BQ79731-Q battery pack monitor
• Perform isolation resistance monitoring
• Fault injection (eg overvoltage, undervoltage, overcurrent, overtemperature)

The BQ79718 is capable of monitoring up to 18 channels, up from 16 channels in the previous generation. With the advent of 800-V battery systems with approximately 200 cells, the system can use 11 18-channel battery monitors instead of 13 16-channel battery monitors.

According to Mark Ng, as one of the main semiconductor stakeholders in the field of vehicle electrification, TI has four main mission statements, which are specifically aimed at solving the main challenges of the industry. TI aims to help OEMs:

1) Make EVs more affordable
2) Increase driving mileage
3) Improve the overall charging experience
4) Make EVs safer

The number of semiconductors used in electric vehicles is growing rapidly as each electronic control unit (ECU) requires large amounts of silicon to perform its duties. In order for automakers to significantly reduce the bill of materials (BOM) and save money by purchasing fewer silicon devices, TI’s goal is to manufacture highly integrated semiconductor devices.

“We also use our 12-inch silicon manufacturing process to manufacture our devices, which ultimately means we are able to deliver ongoing cost savings through manufacturing efficiencies from one silicon generation to the next. monitors as an example,” said Mark Ng.

When it comes to driving range, Andrew Ng emphasized that the state of charge cannot be measured directly, so it can only be calculated based on the ability of semiconductor devices to measure voltage, current and temperature. “The more accurately we can measure voltage, current and temperature, the more accurate the state of charge will be,” said Mark Ng.

The 1mV accuracy of the BQ79718 battery monitor helps automakers better estimate the battery’s overall state-of-charge, which is an indication to the driver of remaining charge and ultimate range.

Test Solutions for Advanced HEV/EV Battery Management Systems
BQ79718 System Diagram (: TI)

Automakers must use advanced power-control topologies and advanced wide-bandgap technologies, such as silicon carbide or gallium nitride MOSFETs, to shorten charging times.

“We have a variety of semiconductor technologies to help the industry achieve this goal, such as our C2000? microcontrollers, MOSFET gate drivers and bias voltage portfolio,” said Mark Ng.

According to TI, the company is committed to developing semiconductor technologies that consider functional safety and are designed to comply with the ISO26262 standard. “Taking battery management as an example, accurate measurements are critical so that the battery is not overcharged or undercharged. Therefore, our battery monitor is designed to meet additional functional safety ASIL-D,” said Mark Ng.

hardware, software, integration

The main goal of battery management systems is to “take care of the battery” and they can be simple or complex and contain a variety of technologies to achieve this. However, these systems can be divided into several groups based on their topology, which refers to how they are deployed and used in cells or modules of a battery pack.

“BMS systems must perform range calculations, state-of-charge, and state-of-health calculations accurately and ensure safety. While most of these parameters require software calculations, the underlying hardware must be as accurate as possible. Range estimation, state-of-charge, and state-of-health require Extremely accurate battery monitor. Again, software relies on hardware to provide functional safety for the entire system,” said Mark Ng.

He added that our battery monitors include multiple channels for high-voltage battery cell voltage measurements. These monitors are also fully redundant, meaning they can meet ASIL-D safety levels. Other devices, such as our battery pack monitors, measure high voltage, control high voltage switches and measure battery pack current. The integration of hardware and software is another topic, and software is even more complex than hardware in some ways. For this, we can use a hardware-in-the-loop emulator to test the hardware and software.

TI’s development platform and comemso’s modular and scalable BMS test bench support BMS development and testing. The test engineer can see the graphic operation and Display settings of these two parts. The project saves BMS developers and manufacturers time and money during development and testing, while reducing project and development planning difficulties and unknowns.

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