The Rapid Charging System For The I.D. R Pikes Peak Is A Science In Its Own Right

•The battery in the I.D. R Pikes Peak must be charged within 20 minutes, according to the regulations

•Sophisticated strategy for rapid charging protects the battery from overheating

•Glycerol is used to generate charging current in environmentally-friendly manner

Wolfsburg (14 June 2018) — The paragraph in the regulations for the Pikes Peak International Hill Climb is clear: Should a participant in the most famous hill climb in the world be forced to suspend their run for safety reasons—for example, should it suddenly start to hail or another car require recovering—they have exactly 20 minutes in which to prepare for their second attempt and to return to the start line. 'This time frame was a crucial factor when configuring the battery for the I.D. R Pikes Peak,' says François-Xavier Demaison, Technical Director at Volkswagen Motorsport. 'Furthermore, the charging strategy and independent mobile power supply are also important aspects of the rapid-charging system.'

Under the leadership of Marc-Christian Bertram, Head of Electrics and Electronics at Volkswagen Motorsport, the team developed the electric drivetrain for the I.D. R Pikes Peak, which generates a total output of 500 kW (670 horsepower). When the Volkswagen Motorsport team attempts to break the existing record for the electric car class on 24 June, it must be ready for countless contingencies. These include a possible interruption. 'When determining the charging strategy, we had to bear in mind a possible re-start,' says Bertram. 'With that in mind, there were two main challenges that had to be overcome: To avoid overheating the battery during the charging process, and to ensure that all the battery cells are charged equally.'

When developing the battery for Volkswagen's first fully-electric racing car, the team benefitted from the expertise in the specialist departments for E-mobility at Volkswagen in Wolfsburg. For example, the fundamental research into the battery for the I.D. R Pikes Peak was carried out in the same laboratories that are being used to develop the battery technology for the future I.D. family of production cars. 'We first tested various chemical compositions of the individual battery cells, then expanded the tests to modular level,' explains Bertram.

The best results came with a lithium-ion battery, which is split and located in two blocks next to and behind the cockpit. The battery has a particularly high power density. 'In the case of a racing car, you are not looking for maximum range, but the highest possible power output,' says Bertram, explaining the differences between the race and production cars. The I.D. R Pikes Peak is capable of accelerating from 0 to 62 mph in 2.25 seconds— faster than a Formula 1 car. The 12.4-mile route includes 156 corners, which means that the battery must be capable of nearly that many acceleration events.

During development, particular attention was paid to the way the battery behaves during the charging process at the racetrack. This process requires a sophisticated strategy. Volkswagen Motorsport works with two rapid-charging systems at the same time in the start area on Pikes Peak, each of which supplies the battery in the I.D. R Pikes Peak with fresh energy at a relatively low total output of 90 kW. 'The low charging current limits heat development,' says Bertram.

The great unknown is the air temperature in the paddock. Even in June, temperatures on Pikes Peak can dip to just above freezing point. However, the teams can also be faced with sweltering mid-summer heat. 'The ideal temperature for the battery is about 86 degrees Fahrenheit,' says Bertram. If necessary, air can be supplied to cool the internal battery system in the I.D. R Pikes Peak. However, cooling must not be too dramatic during the rapid-charging process, in order to avoid the build-up of condensation.

Volkswagen Motorsport is also using innovative methods to generate the energy required to charge the battery. Because the temporary paddock, located at more than 9,000 feet above sea level, does not have a suitable power supply, a conventional looking generator is used to produce the electricity required by Volkswagen Motorsport. However, unlike conventional generators, this one runs on Glycerol, rather than diesel.

Glycerol is a sugar alcohol that is a by-product from bio-diesel, for example, and combusts with virtually no harmful exhaust fumes or residues. The liquid itself is non-toxic and is even permitted as an additive (E422) in the food and cosmetics industries. 'The Glycerol-powered generator not only supplies the I.D. R Pikes Peak with environmentally-friendly electricity before the practice sessions and the race,' explains Marc-Christian Bertram, 'but also all the electrical devices in our pit area during the race, from the engineers' laptops to the coffee machine.'

Photo credit: Volkswagen
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