Changing What is Possible on the Racetrack
The previous two articles in this three-part series examined the limitations of current Electric Vehicle (EV) embedded electronics systems and key components for Battery Electric Vehicles (BEVs) and Formula E race cars. This article serves as a capstone to this series, detailing how developments in EV embedded electronics are leading to new, exciting vehicles on and off the racetrack.
Critical Functions of EV Embedded Electronics
With the latest EVs, virtually all vehicle functions are controlled and monitored by intelligent electronic systems with a plethora of sensors. These electronics are very different from consumer electronics, as they are rated for much higher levels of reliability and for more demanding environments. ISO 26262 establishes road vehicle functional safety parameters, which involves a set of standards of reliability designated by Automotive Safety Integrity Levels (ASIL). It is vital for automotive electronics to be held to higher-level ISO 26262 standards to ensure road safety, years of reliable vehicle operation, and failure modes that do not lead to dangerous states.
Three of the main areas for EV embedded electronics are automotive-grade Micro Controller Units (MCU) or Micro Processor Units (MPU), Battery Management System (BMS) electronics, and diagnostic sensors for fault prevention. In the latest season of Formula E, Renesas designed and deployed modules containing Renesas MCUs and BMS devices, along with various supporting components and sensors. These key devices were the ISL78714 series of BMS ICs and an RH850 variant MCU.
The Renesas BMS IC monitors and manages the charge on up to 14 battery cells for a single device. Ganged configurations using multiple BMS ICs are possible, which can achieve a full common pack size of 96 cells, or can be configured to accommodate a wide range of cell configurations. The ISL78714 device family has among the highest battery voltage measurement accuracy ratings (better than +/- 2 mV per cell), which enables much more effective cell balancing and charge state information [1,2,3]. This BMS IC is also able to scan the cell voltage in under 20 microseconds, enabling extremely fast and accurate monitoring of battery cells under transient use conditions. These BMS ICs also have several integrated temperature inputs along with a variety of other monitoring, diagnostic, communications, and measurement features that make them an ideal choice for performance Li battery monitoring.
Another indispensable component of high-performance EVs are automotive-grade processing units, such as MCUs. MCUs can be programmed to provide enhanced control, monitoring, and diagnostic features, and if qualified, can ensure Functional Safety features. An automotive-grade MCU is the brain of an EV and its subsystems. With advanced control system functions, these MCUs can be used to gather and analyze detailed EV operational information and enhance EV performance from this wealth of data. This data can also be further analyzed by engineers to make vehicle design improvements and enhance tuning procedures.
In the case of Mahindra Racing’s Formula E race car, a Renesas RH850 family MCU was used to augment the low-voltage BMS module to provide enhanced intelligence features and gather performance data while the race car was on the track [4,5]. This data not only aids Mahindra Racing tuning their already-high-performance EV, but it can also be used by Renesas to better design components for EV and automotive applications . Of course, the benefits of an MCU are only as great as the hardware designers’ and software developers’ capabilities, which is why Renesas engineers work side by side with Mahindra engineers to achieve their goals faster .
The world of EVs, on the race track and off, is an exciting and growing field rich with technical challenges and new solutions. The next few decades will likely see the rise of EVs and autonomous vehicles and a diminishing of traditional personal transportation systems. It is certainly an exciting time to be at the forefront of EVs, developing vital EV embedded electronics and systems.
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