Porsche is claiming a “world first” for production cars with its optional fitment of a lithium-ion starter battery for its GT3, 911 GT3 RS, and Boxster Spyder models. Weighing just under 6 kg (13 lb), it is more than 10 kg (4.5) lighter than a typical 60-A·h lead-acid battery.
With the credibility of Li-ion technology as a power source for electric vehicles now a given, the move to a more mundane application is significant, albeit at a very considerable added cost: €1904 including tax or, as an aftermarket fit, €2499 including tax from Porsche Tequipment. It will be available on new cars from January.
Because its recommended thermal operating range is relatively narrow—0 to 32ºC (32 to 90ºF) ambient conditions—the battery, developed by Porsche in collaboration with specialist company GAIA (part of LTC), is delivered as a separate unit that the car owner may then fit it as an alternative to the conventional battery. The weight savings achieved would be particularly apposite for motorsport events.
The battery uses a wound film of carbon and iron phosphate with a ceramic film, moisturized by electrolyte, that acts as a separating layer between the two. Porsche stated that compared with other types of Li-ion batteries that use a combination of manganese oxide, cobalt oxide, or nickel, the Li-ion-phosphate type has particular pluses as an engine starter battery, being robust and possessing the ability to “consistently” guarantee 12 V for the car’s onboard systems.
It comprises four cells. A management system protects it against major discharge and has been developed to guarantee a consistent charge level within each cell. If the battery’s voltage drops below a specified level, a warning is sounded.
Although its length and width are equal to those of a conventional battery, it is 70 mm (2.8 in) shorter. Fastening points, electrical connections, and voltage range are all compatible with each model. For track work, battery changing is a quick and simple task.
Nominal capacity of the new battery is 18-A·h, but because of far greater efficiency it is said by Porsche to offer a level of practical output and performance that is comparable or superior to that of a regular lead-acid 60-A·h battery. A conventional lead-acid battery typically has only about 30% of its capacity available for practical use; the new Li-ion battery is said to provide almost 100% thanks mainly to “the independence of the chemical composition of the electrolytes from its charge status,” according to Porsche.
The new battery is also said to provide its full power when starting the engine, almost independently of the current charge level, and delivery of power throughout its useful charge range is also significantly superior. After the engine start sequence, the Li-ion battery can recharge more quickly than a lead-acid type.