source: EDN article
Steve Taranovich -October 19, 2015
Automobile manufacturers will need to lower CO emissions to meet government standards over the next ten years. Plus, fuel efficiency is in demand by automobile owners. Ultracapacitors have found their way into the automotive ecosystem in areas such as regenerative braking, start-stop systems, active suspension systems, voltage stabilization, electric turbochargers, and more.
Maxwell Technologies, Inc. recently announced that Continental Automotive Systems’ Maxwell-powered voltage stabilization system (VSS) will be a standard feature on 2016 Cadillac ATS and CTS sedans and ATS coupes, excluding the ATS-V, CTS-V, and CT6 models. General Motors is the first North American automotive original equipment manufacturer (OEM) to integrate the Continental ultracapacitor-based voltage stabilization as part of the enhanced start-stop system, which lowers fuel costs, improves performance and reduces emissions.
In start-stop systems, the internal combustion engine is turned off when the driver stops and the engine is restarted when the driver accelerates, which lowers emissions and improves fuel economy. Battery-based start-stop systems can be enhanced with an ultracapacitor-based voltage stabilization system implementation which enables the burst power needed to restart the engine, which reduces high currents and repeated cycling that can shorten battery life. The voltage stabilization electronic control results in a smooth start, reduced engine vibration and a superior driving experience. Maxwell’s ultracapacitors, in Continental’s VSS design, also serve as an additional power source for stabilizing the vehicle’s electrical system during periods of high power demand.
Continental’s VSS system contains a control unit called the power electric unit (PEU) and a power storage unit called the energy storage system (ESS)—that’s where the ultracapacitors are. The ESS has a small battery in series with two double-layer capacitors. To re-start an engine, a good amount of energy is needed so the excess energy is stored in the ESS for that purpose. The PEU handles the charging of the ESS as well as controlling the accumulated stored energy.
Continental’s VSS system, showing their millionth start-stop system produced. The start-stop-system can automatically stop the engine at red lights. (Image courtesy of Continental)
In standard automobile systems, the negative terminal of the battery is connected to the automobile’s metal chassis, but in start-stop systems, the chassis connection is made by the control unit to ensure that the power storage unit is chargeable and that the automobile is able to retrieve the energy from there. This system can save as much as 10% fuel while lowering carbon emissions.
Unlike batteries, which produce and store energy by means of a chemical reaction, ultracapacitors store energy in an electric field. This electrostatic energy storage mechanism enables ultracapacitors to charge and discharge in as little as fractions of a second, perform normally over a broad temperature range (−40°C to +65°C), operate reliably through 1 million or more charge/discharge cycles, and resist shock and vibration.