Porsche will offer a lithium-ion starter battery option—the first automaker to do so—as of January 2010 for the 911 GT3, 911 GT 3 RS, and Boxster Spyder. Weighing less than 6 kg (13 lb), the new battery is more than 10 kg or 22 (lb) lighter than a conventional 60 Ah lead battery.
The 12.8V, 18 Ah lithium iron-phosphate pack from Gaia is delivered as a separate unit together with the car and may subsequently be fitted as an alternative to the regular, conventional starter battery. The cars are delivered with both batteries; while the lightweight battery offers a very high standard of everyday driving qualities, Porsche says, its starting capacity is limited at temperatures below 0 °C (32 °F) due to its specific features.
Li-ion batteries, given their current pricing, are generally not expected to have much penetration in the SLI (starting, lighting, ignition) battery segment. (Dr. Menahem Anderman of Advanced Automotive Batteries calls the SLI business “a long shot” for advanced batteries such as Li-ion.) Porsche’s new lithium-ion battery will be available as an option delivered with the car, selling at a price in the German market of �,904 (US$2,900) including 19% value-added tax.
Porsche’s primary reason for developing and introducing the new battery was its lower weight to enhance performance and dynamics.
In its length and width the lithium-ion battery comes in the same dimensions as the regular battery, but is approximately 70 millimeters or 2.8" lower. The fastening points, electrical connections and voltage range are fully compatible with the respective models, allowing simple and quick replacement of the standard lead battery by the lightweight unit, for example when racing on the track.
With its nominal capacity of 18 Ah, the lithium-ion battery, through its specific features, offers a level of practical output and performance not only comparable to that of a 60 Ah lead battery, but better in many cases, Porsche says.
On a conventional car battery only about 30% of the total capacity is actually available for practical use due to the configuration of the system, while this restriction does not apply to the lithium-ion battery. Delivery of power by the lithium-ion battery throughout its useful charge range is likewise significantly better, providing its full power, for example, when starting the engine almost independently of the current charge level.
After the engine has started, the new Porsche battery shows further benefits in the charge process, being able through its smaller internal resistance to take up more power than a conventional battery and thus re-charge more quickly.
Other benefits include a significantly greater number of charging and discharging cycles; a lower self-discharge; and longer service life.
The lightweight battery is made up of four cells and integrated control electronics. This battery management system protects the battery from major discharge and guarantees a consistent charge level within the individual cells. Once battery voltage drops below a certain threshold, a warning signal reminds the driver to re-charge the battery either simply by driving the car through the power of the engine running or by means of a conventional battery charger.
