Within the next ten years, electric vehicles are expected to account for 90 percent of the market, including full-electric vehicles and various versions of hybrid vehicles. Many new test benches for e-mobility and batteries are being built. So what are the key points we need to understand for this new type of bench? How can we find our way around this new world of tests for electric or hybrid vehicles?
The list of challenges is long. First, and most importantly, are battery tests. Today’s lithium ion batteries provide an energy density 20 to 30 times inferior to gasoline, and to achieve cost parity with a petrol-driven vehicles, we have to cut their costs four-fold. This cannot be done overnight, but the calibration of the BMS (Battery Management System) must be optimized immediately, which requires precise means of optimization on the test bench. For battery test benches, a highly automated and staff-saving process is required. It must be able to react and supervise all the test benches in real time. File formats must be identical, irrespective of their source. In some centers, each device has a different file format, which affects the center’s productivity. In addition, safety is a prime concern with batteries. Great attention must be paid to extreme conditions, in which the internal chemistry in the battery can go out of control. Severe battery tests are necessary, including fire tests, overvoltage tests, crash tests or tests in which the battery goes completely discharged. While the battery is the most sensitive element to be tested, testing electric motors also presents technological issues. Upcoming motors can reach up to 25,000 rpm. In some phases, the temperature suddenly rises, to the detriment of the motor’s longevity. In this case too, the optimization of the global Energy Management System (EMS) will allow critical cases to be managed, increasing the life span of the e-motor.
FEV summarizes the keys to e-mobility test center and system development by highlighting three points: the automated management and global supervision of the processes and the test benches, using the FEVFLEX™ and MORPHEE® software suites. The standardisation of test bench solutions, or Test Cell Products. And, the calibration of the controllers and the optimization of energy management, which demands the extended use of simulation. This vision is the result of more than ten years of experience, with two test centers in Munich and Saint Quentinen-Yvelines (France), equipped with 22 test benches to test batteries, and numerous e-motor and e-axle cells.
Fully automated process
A fully automated process is a key factor in any modern test center, but it is particularly important in battery test centers. This is done through software, such as FEVFLEX™ and MORPHEE®. FEVFLEX™ is a modular software suite dedicated to manage and monitor the entire test field. All the information sent to FEVFLEX™ is produced by MORPHEE®, FEV’s automation system. The electric revolution is only just starting. Batteries, electric motors and general vehicle architectures are set to evolve even further. In this respect, FEVFLEX™ and MORPHEE®’s upgradeability and applicability makes it a complete must. These open tools can be easily configured by the user, at no additional development cost. MORPHEE can be connected to all types of devices using the same programming interface. It produces and synchronises result files in an identical format, irrespective of the equipment used.
Test cell products: standard solutions
2019 will be a very special year for FEV Software and Testing Solutions , with the launch of the test cell products and standard test bench solutions. Over the years, many benches have been built, both on FEV’s own sites and on customer sites in Europe, Asia and America, ranging from complete engineering projects, to simple automation. FEV has built on this experience to develop standard test bench solutions, or test cell products, that use FEV’s products and products from approved suppliers. Thanks to this standardization, FEV can control costs and propose shorter deployment cycles. This offer covers all the necessary dimensions of the field of electric vehicles, and the safety-related aspects in particular.
FEV proposes battery test benches covering every test case: cell benches with up to 24 cells per climate-controlled chamber, module benches with up to six modules and integrated pack benches, either in walk-in chambers, or in king-sized climate-controlled chambers.
FEV also proposes standard e-motor test benches that can be used to characterise electric motors. The key aspect of this type of test bench is its ability to test at very high speeds and in a highly-dynamic process where vibrations are taken into consideration. FEV produces state-of-the-art e-motor test benches, including dynamometers. It offers e-motor test bench solutions enabling rotational speeds of 25,000. The MORPHEE® solution used to control the bench replaces the bench controller, offering very easy connectivity with the calculators. The e-powertrain is optimized by taking several use cases (motorways, urban environments or rural areas) and several factors (voltage and current signals, frequency versus angular position and speed, transient torque management etc.) into consideration. In this case, FEV’s OSIRIS® Powermeter serves to analyse the efficiency of the e-powertrain system by measuring the power before and after the inverter and before and after the e-motor.
FEV offers unique solutions facilitating not only the optimization, but also the validation of the complete driveline. Durability tests simulating mechanical cycles (vibrations, reducer, differential) and thermal shocks (cooling, rotor thermal management) must also be conducted. In this configuration, a good solution is to test not only the e-motor, but also the complete drive chain. On the so-called e-axle test bench it is possible to test the entire system in the downstream steps of the development process and involves using both MORPHEE® and OSIRIS®, as well as FEV dynamometers and conditioning units for fluid cooling – the so-called eCoolCon™.
Energy Management System optimization
The final key factor of success of an e-mobility test center is its capacity to optimize the calibration of the various calculators and the EMS (Energy Management System) of the drivetrain. This was already one of FEV’s strengths in the field of conventional engines, and it is still the case with electric or hybrid motors. FEV has achieved this by developing tools with two characteristic features: a very high level of performance and complete compatibility with one another. In the initial development phases, xMOD™, a virtual experimentation and co-simulation platform, creates a system that was complex to develop by co-simulating the different models that describe it: the electric motor, battery, driver, complete vehicle, etc. Consequently, virtual experiments can be made on the same platform in order to prevalidate the control laws. In the following step, the bench controlled by MORPHEE® – in this case the battery and BMS bench or the e-powertrain bench – is used to integrate the previously validated models by replacing the battery or e-motor model by the physical part, and by keeping all the other parts to produce the most accurate representation possible of the drivetrain in its environment. Since xMOD™ and MORPHEE® share the same DNA, the interfaces, tests and models all follow the same process, from the beginning to the end, in what FEV calls the Collaborative Framework. It should also be noted, that the exceptional simulation performances of these tools, which are 10 to 40 times faster than any other solution on the market, enable highly complex models to run on the test bench in real time.