Lightweight Garage #1 Lithium iron phosphate starter battery @ Porsche 911 GT3 RS (997.2)

May 12, 2021 from Florian Wätzold

©Bernulius/stock.adobe.com

The Vehicle

Behind the first garage door we parked the Porsche 911 GT3 RS (commonly known as 997.2). The car weighs about 1,445 kg and its six-cylinder boxer engine develops a maximum output of 450 hp and delivers up to 430 Nm of torque.

© Porsche

This car with manual transmission was built from 2009 to 2011 to obtain race car homologation. In addition to the use of carbon fibre, aluminium struts, and polycarbonate windows, it also became the first car with a lithium-ion starter battery in February 2010.

The Technology

For the first time, Porsche used a positive electrode made of lithium iron phosphate for starter batteries in selected models. This is a special application because lead-acid starter batteries have been established since their introduction in a Cadillac over 100 years ago and are still state of the art. Whereas in conventional starter batteries disordered chemical reactions build up or reduce the electrode, lithium batteries intercalate lithium into the grid structure.

Although the lithium iron phosphate technology used at that time was still very temperature-sensitive and could not provide the required starting power below 0° C, it was charged faster during operation and offered a longer service life.

The new starter battery also met the usual installation standards and could be retrofitted or replaced at the racetrack. The cost of the battery was approximately 2,000 € or for retrofitting 2,500 €.

The Lightweighting Effect

Special feature of this solution from a lightweighting point of view was reducing the overall height by approximately 70 millimetres and a total weight of approximately 6 kg. This is a weight reduction of 10 kg compared to the 60 Ah reference starter battery.

© Porsche

Due to the higher energy density and the advantageous discharge behaviour, this technology enables the possibility of using the available package for other purposes or optimising the installation position, for example to improve the centre of gravity. The weight reduction in a sports car also effects the driving performance. A low mass allows faster acceleration as well as tighter curving.