Cleantech Market Intelligence
No Halt to Stop-Start Vehicle Technology Advances
The latest Pike Research report on Stop-Start Vehicles has been published for less than a month, and already more new developments have emerged. On October 2, Lamborghini said it will implement a stop-start system from Continental that features Maxwell ultracapacitors. All models of the Aventador, which goes into production in late 2012, will feature the new system. Using ultracapacitors to handle the electric power surge required to start the V-12 engine in 180 milliseconds allows the company to reduce the size and weight of the battery. The stop-start system is estimated to contribute about 7% of the 35% goal (by 2015) that Lamborghini has set to reduce the CO2 emissions of its new models.
System design was reportedly done by Maxwell’s Italian distributor Dimac, with production responsibility handed over to Tier One supplier Continental. Undoubtedly Continental’s experience supplying Maxwell’s ultracapacitors to PSA Peugeot Citroën for its second-generation e-HDi stop-start system were a factor in landing this business.
On October 3, Tier One supplier Denso debuted a Li-ion battery pack designed specifically for stop-start applications. The system comprises high-power battery cells from a Tier Two source packaged with a power supply control switch and a battery management unit to monitor the charge levels. The pack is designed to be air-cooled and does not require any additional hardware to modulate the temperature. The system is reportedly going into production on the Suzuki Wagon R this month.
These two announcements illustrate different approaches to address the practicalities of powering a stop-start system. With a charge-discharge cycle rate of typically 10 times that of a conventional vehicle, the traditional automotive battery simply cannot cope, and most production systems feature heavy duty absorbed glass mat batteries. As Li-ion cells get cheaper thanks to the hybrid and electric vehicle usage demand that is pushing volumes up, the greater power capacity is attractive for stop-start systems. The alternative is to keep a low-cost basic battery to handle the steady loads of lighting, ignition, information and entertainment systems, and HVAC, and supplement it with a high power device such as an ultracapacitor to handle rapid charging and discharging. Both systems require robust electronics to manage the stored electrical energy effectively.
Both these systems have advantages and disadvantages, and as with most things automotive, the tradeoffs are in cost, size, and performance. We expect to see further announcements of new batteries and energy storage technologies for stop-start systems in the coming months as OEMs begin to implement the fruits of their recent research. Evidence of this in the United States, where the EPA testing doesn’t include enough stopping to demonstrate the practical benefits of stop-start technology, can be seen in Ford’s recent PR efforts to raise awareness. Those benefits are too important to ignore under the pressure of increasing legislation and the consumer demand driven by rising fuel prices.