Automotive Start-Stop

By 2025, U.S.-made vehicles must average 54.5 miles per gallon. Automakers have an intensified focus on innovative system designs to meet efficiency standards being established worldwide.

Engine start-stop is one function that helps manufacturers achieve fuel economy standards in conventional or hybrid-electric vehicles: The system turns off the engine when the car comes to a full stop and restarts when the foot is taken off the brake. Engine start-stop prevents idling, saves fuel, and reduces emissions, satisfying the consumer’s desire for improved fuel economy and helping manufacturers meet regulations. Today, over 2.5 million cars are powered by Maxwell Technologies’ ultracapacitors for engine start-stop.

How We Enhance Engine Start-Stop Performance

start stop ultracapacitor solutions

When integrated into a battery-based engine start-stop system, our proprietary ultracapacitor energy storage technology delivers burst power to re-start the engine, relieving the car’s battery of high current, repetitive cycling that often shortens battery life.

The ultracapacitor system allows the starter to be separated from the 12-volt boardnet, thereby eliminating voltage sags (decreases in voltage during times of high power use) and improving system-wide energy efficiency.  

The ultracapacitor-based voltage stabilization capability enables fast, smooth engine starts and reduces engine vibration, improving driver experience.

Drive Past Design Roadblocks.

Maxwell’s ultracapacitor energy storage solutions offer automotive manufacturers a variety of opportunities to transcend the limitations of current battery technology. Our automotive customers leverage the advantages of ultracapacitor cell technology for engine start-stop:

Offers high cycling capability (hundreds of thousands of cycles), resulting in long service life

Operates from –40°C to 65°C and resilient in ambient temperature swings

Improves system power performance and voltage stability

Provides options for smaller, light-weight energy storage modules that require less space for under-the-hood applications

Qualifies for high vibration and shock environments, meeting ISO16750-3 Table 12, IEC 60068-2-27 and IEC 60068-2-29 international standards

Provides unmatched quality due to Maxwell’s unique dry electrode manufacturing process


Power vs. Energy: Our Hybrid Energy Storage Approach

As vehicles become more advanced in performance, safety and entertainment features, the difficulty lies in meeting the vehicle’s need for both high peak power and long-term energy. Automakers face complex design decisions in terms of energy storage, including determining whether to take an island approach that addresses individual applications, or a centralized energy storage approach that addresses multiple vehicle applications.

Maxwell Technologies is a proponent of a hybrid energy storage approach—batteries perform optimally when serving a vehicle’s long-term energy needs, and ultracapacitors cover short-term, high-power demands. In our long-term, collaborative partnerships with automotive customers, we’ve found that the combination of ultracapacitors with batteries offers the versatility needed to fulfill the energy and peak power demands of advanced automotive designs.

"Continental’s voltage stabilization system uses Maxwell's ultracapacitors as an affordable option for automakers to create a more positive driving experience for their customers.”

—Jon Buckles, program manager for hybrid electric vehicles at Continental Automotive Systems

General Motors

First U.S. automotive OEM to adopt ultracapacitors for engine start-stop

Continental Automotive Systems’ Maxwell Technologies-powered voltage stabilization system (VSS) is a standard feature on 2016 Cadillac ATS and CTS sedans and ATS coupes (excluding the ATS-V, CTS-V and CT6 models). In 2015, General Motors became the first North American automotive original equipment manufacturer to integrate the Continental ultracapacitor-based VSS as part of the car models’ start-stop function. In addition to seamless engine starts by providing burst power, Maxwell’s ultracapacitors also serve as an additional energy source for stabilizing the car’s electrical system during periods of high power demand.


Integrates Maxwell’s ultracapacitors for start-stop idle elimination system

Lamborghini integrated Maxwell Technologies’ six-cell ultracapacitor module for the start-stop idle-elimination system in its luxury brand Aventador sports cars. The ultracapacitor system, designed by Maxwell’s distribution partner Dimac and manufactured by Continental AG, provides added cranking power for efficient restarting of the 12-cylinder, 700-horse power Aventador and significantly reduces size and weight of the battery system.




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