Over the next 10 years, electric vehicle (EV) growth is expected to accelerate rapidly as advancements in technology and increased government incentives drive adoption. The number of EV models available on the market is expected to increase, and the cost of EVs is expected to decrease as economies of scale come into play. Battery technology is also expected to improve, resulting in longer range and faster charging times. Additionally, more charging infrastructure will become available, making it easier for consumers to charge their EVs. As a result, it is predicted that by 2030, EVs will make up a significant portion of the global vehicle market. Global regulators are working to ensure that these vehicles will be as safe as, or safer than, the traditional internal combustion models they replace.
MGA’s history with battery testing spans 40 years, starting in the 1980’s with abuse testing on coin cells. Within the past 15 years MGA’s services have expanded to include electric vehicle testing in crashworthiness and automotive battery abuse and durability testing. MGA recently demonstrated the ability to conduct Battery Management System (BMS) evaluations at the full vehicle level to support advancements in battery system safety and the development of global regulations.
Testing can be performed at the component or system level, and often a mixture of both is utilized by engineers to design, develop, and validate their innovations. MGA's recent efforts in BMS evaluations are related to the full system, or full vehicle, testing of an electric vehicle to the proposed requirements of the Electric Vehicle Safety (EVS) Informal Working Group (IWG) Draft Global Technical Regulation No. 20 (GTR No. 20). The requirements outlined in GTR 20 evaluate the Rechargeable Electrical Energy Storage System (REESS), or battery, in a variety of real-world scenarios, including overcharge, over-discharge, overcurrent, and external short circuit. These electrical tests validate the battery management system’s ability to apply a countermeasure prior to the REESS experiencing any damage or presenting a hazardous situation. A quick break down of each test method is provided below:
Overcharge of the battery can occur due to a failure of the charging system, a sensor failure, or a voltage reference drift. In these events it is possible that the charging system continues to supply charge current after the battery is fully charged. To simulate this scenario a high voltage battery charger is connected to the vehicle and programed to provide the overcharge required for the test. The battery temperature and vehicle response are monitored, and the test typically concludes when the BMS protection terminates the charge current.
Over-discharge is unlikely to lead to a hazardous situation, however the subsequent charging of an over-discharged battery has risks. To mitigate this risk the vehicle shall have protection measures against over-discharge during operation. An external load draws current from the battery and is programmed to drain the battery below its normal operating specifications. The battery temperature and vehicle response are monitored, and the test typically concludes when the BMS protection terminates the discharge current.
Overcurrent during DC charging due to the failure of the external charger controls can result in overheating and damage to the battery. Vehicles capable of DC charging must have protection measures in place to prevent overcurrent. This failure mode is created in the lab by using a high voltage battery charger in parallel with a commercial DC fast charger. The high voltage battery charger supplies an increasing amount of overcurrent after the test begins, and the vehicle response and battery temperature are monitored. The test is completed when the BMS interrupts the charge current.
External short circuit verifies the protection measures in place in the event of a short circuit occurring outside of the battery. MGA operates a 50,000 kA short circuit machine developed internally by our equipment fabrication department to execute this test. The vehicle’s high voltage system is connected to the short circuit machine by attaching a breakout harness to the high voltage bus outside of the battery. At the beginning of the test the contactor in the short circuit machine is closed, providing a short circuit between the positive and negative high voltage buses. MGA monitors the bus voltage, current through the short circuit machine, and battery temperature throughout the test and for a period after the flow of current has been terminated. Typically, the battery will have protection measures, such as a pyro-fuse, that responds quickly to stop the flow of extremely high current in the event of an external short circuit.
Over-temperature testing confirms protection measures can manage overheating due to operation, or the failure/reduced function of cooling systems, to prevent a hazardous situation. The vehicle is heated to 40-45°C in a temperature chamber for at least 6 hours prior to the start of the test. The vehicle then undergoes charge/discharge cycles to raise the temperature of the battery. The cycles are achieved by driving the vehicle on a dynamometer and observing the vehicle’s response. The test concludes after 3 hours of operation, if temperatures stabilize over a 2-hour period, or charge/discharge operation is terminated by the BMS.
MGA’s staff is grateful for the opportunity to work in the advancement of safety in all the industries we serve, and is excited for the new innovations electric vehicle, energy storage, and control technologies that are on the horizon.