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TECHNOLOGY – PEUGEOT 908 HYBRID4


sense that a fourth car should be run to generate comparable data to the three cars that would race. However, Peugeot announced that, if it were to run a hybrid at the test, it would be one of the three cars entered for the race. At the time it made no sense but, by running the hybrid system in the gearbox bellhousing, they could convert a car from hybrid in the morning to a standard car in the afternoon. The carbon bellhousing, designed by Peugeot Sport and built by Ricardo, was adapted specifically for the job, but the team was struggling with reliability, so ultimately elected not to run the system at the test day as it suffered a leak in the cooling system.


‘Our initial idea was to put the battery pack in the bellhousing,’


BUILDING A BATTERY


Peugeot took the decision to build its own batteries under the guidance of Pierre Calippe, head of electronics, and was taking no chances. Away from the workshop and hidden away in the storage and spare parts unit, an unassuming room was built specifically for the job, and contained all the safety features Peugeot Sport felt necessary. The hybrid system included a 120kW motor and a small gearbox to adapt the ratio of the motor to the diesel engine. ‘Without the gearbox, the motor is approximately 7kg,’ says Calippe. ‘The power inverter connects to the motor and this is 3kg. Because we don’t have an alternator, we have a 2kg DC/DC converter that converts the high voltage battery to the 14V for the car. These are the principal components. ‘All the cells in the main


battery are oil cooled, with an oil flow. All the monitoring of the battery is done by a large board that was developed internally. It measures temperature, voltage and also controls all the relays and makes it completely safe. ‘There are different layers,


into which you can fit the cells – 90 in total – and they are connected in series by the aluminium bars. The concept is simple, so it can be built quickly.


‘The time taken to build one was one week, but we were able to disassemble and re-assemble in one long day. This board fits on top of the box with no wires, for reliability issues.’ The triangular battery, which


weighed 26kg empty, and an extra 4kg when full of oil, was designed specifically to fit inside the Peugeot-designed, Capricorn-built chassis, as low as possible, yet still accessible in case of a problem. ‘We have a mechanical switch


that you can move inside the car, so if you need to work on the car, even if you cannot see what the state of the car is, you can disable it and the car is safe. It also works in case of an accident.


This was going to be standard. The rule says you should have something to disconnect, and that at a specific place there is a switch that controls the relay, but not necessarily the mechanical system. Battery power was 350V,


so not tremendously high, and there was a system to split the voltage in the event of an accident. However, one of the main worries for the team was how to recognise when there was a fault, and so Peugeot designed an ingenious system to alert the team in the pits, or marshals out on track, in case of an accident, whether or not the car was live, and safe. ‘The regulation says that whenever


you switch on the high voltage power, you have a red light switched on, but we have added more,’ says Calippe. ‘There is a small red circle, and a green ring. If the green ring is on, the car is safe. It doesn’t tell you if there is high voltage or not, just that the car is safe and that you can touch it without risk. The red tells you there is power. ‘If the car comes to the pit


and the red is on, but not the green light, you put on the gloves. We discussed this with the FIA and they said this is what they want. They said the main switch should also control the high voltage. In the car, you have the hybrid master switch, which has a green LED for the driver. If the green is not on, it usually means it is not dangerous, just that there is an insulation problem, something not going well.’


The 26kg battery was designed and built by Peugeot Sport. The first versions were water cooled.


explained Jansonnie. ‘Finally, though, we considered it too difficult. It was possible, but there was a lot of risk. The volume was not enough. ‘At the last moment, when


we could still make big changes on the 2012 tub, we made the decision to change.’ The first two generations


of gearbox-housed batteries were water cooled, but the team


experienced problems in two tests, and switched to the more traditional oil-cooled method for the third generation, with the battery pack in the tub. ‘The water-cooled battery


The 90 individual cells in the 350V battery are contained within different layers with aluminium bars connecting them. Peugeot developed a warning light system that informs whether the car is live and / or safe to touch


July 2012 • www.racecar-engineering.com 61


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