As the electrification of automobiles continues to accelerate, the need for a safe, reliable, high-power energy-storage technology is greater than ever. Ultracapacitors already have an established place in Voltage Stabilization Systems (VSS) for internal-combustion engine (ICE) stop-start applications. By providing additional voltage support during a high-current cranking event, voltage levels are maintained to allow proper operation of accessories without interruption and enable proper operation as battery state-of-health declines.
The nearly five million stop-start systems in production-car use today include vehicles such as the PSA 308 and many other diesel platforms, several General Motors vehicles and even current stop-start/hybridized models from supercar legend Lamborghini. In racing, Toyota used ultracapacitors in its highly successful LeMans TS040.
With continued pressure on automotive OEMs to reduce CO2 emissions, stop-start systems have become a standard feature, not just an upgrade option, for many global ICE and hybrid-electric vehicle (HEV) platforms, but major OEMs such as GM, Ford, Stellantis, and others now have aggressive targets of 40-50 percent fully electric vehicle (EV) sales by 2030. To meet these goals, there is heavy investment in electric drivetrains as well as redesigns of nearly all electronic systems in the vehicle. Analysts expect $330 billion or more to be spent on light-vehicle electrification over the next five years.
Examples of automotive applications for which ultracapacitors are in use:
Circuits to enable recessed door handles to pop out in case of an accident or loss of power. Having a stored burst of high power available to open the door from a secondary energy source, an ultracapacitor, is not only practical but also a safety feature that can save lives.
Accessory power applications that include: Electronic Power Assist Steering (EPAS), Electronic Power Assist Braking (EPAB), as well as power liftgate and plow features.
In autonomous driving vehicles where an emergency backup energy source is required, ultracapacitors can provide the short-duration power needed to get the vehicle to the side of the road in the event of a failure of main drivetrain power.
Body electrical systems including door, seat, window, trunk and other electrically actuated subsystems.
Customer amenities such as electrically driven air-conditioning, quick heat for seats, steering wheel and passenger cabin.
Many automotive-related safety-critical loads typically are short-duration, highpower situations. Powertrain functions such as power boosting and energy recuperation, as well as body electrical systems are medium-term loads. Although batteries are ideally suited to deliver energy for long-term events, such as cabin air-conditioning during the idle-stop mode of an ICE stop-start system, they are not designed to satisfy the most important requirements of short- and medium-term loads: to provide bursts of power in the seconds time frame over many hundreds of thousands of cycles.
Compact in size, ultracapacitors can deliver much higher peak power compared to batteries and store an incomparably higher amount of energy than conventional capacitors. Ultracapacitors from Maxwell Technologies offered under the trademark DuraBlue, for example, currently are available on the market in larger cylindrical-format cells with capacitance up to 3000 Farads. These cells incorporate advanced shock and vibration technology and when combined with Maxwell's patented electrode formulation and manufacturing process, result in a product line specialized for the most demanding requirements of the transportation industry.
For applications requiring a smaller form factor, Maxwell has developed a 325F cell, the BCAP0325. A high-power cell with ultra-low Equivalent Series Resistance (ESR), it is ideally suited for automotive applications. The cell is AEC-Q200 qualified and provides one of the longest lifetimes available in the industry. Feature and performance metrics include:
Small (33 mm) form factor
1 million cycle capability
Compliant to UL, RoHS and REACH standards
Safety-Critical X-by-Wire Applications of Distributed Power Modules
An electrical system architecture with modular and distributed power modules is one method of addressing the need for power and redundancy required by the safety-critical and security systems in automotive applications. Distributed ultracapacitor modules alleviate electrical distribution system voltage sag and transients by supplying peak power locally, while requiring only the average power from the vehicle's primary power supply. This essentially decouples the high transient power load from the vehicle's primary power supply system.
A further requirement of safety-critical applications is the necessity of redundant power supply in the event of loss of the main electrical distribution system branch circuit for x-by-wire functions. Distributed power modules located at critical loads, such as electric power-assist steering system, offer the vehicle designer additional redundancy for safety-critical applications.
As outlined above and prevalent in the market today, ultracapacitors are an excellent tool for vehicle engineers to specify in support of high-power, short-duration loads. With their extremely fast charge and discharge capabilities, unmatched cycling durability, wide operating temperature range, long lifetime and environmentally friendly design, ultracapacitors offer many benefits in a small, lightweight package. Maxwell Technologies’ line of DuraBlue and AEC-Q200 qualified ultracapacitors are ideally suited to meet these demands.
This article was written by Troy Brandon - GM, VP Marketing, and David Wright - VP Engineering, UCAP Power, Maxwell Technologies (San Diego, CA). For more info visit here .