PSA's new stop/start system uses ultracaps for energy storage, extra power

  • 21-Jun-2010 05:09 EDT
The e-HDi architecture includes ultracapacitor e-booster developed by Continental and a Valeo belt-driven integrated starter/alternator.

PSA Peugeot-Citroën has unveiled its second-generation micro-hybrid system, to be known as e-HDi initially. The new system, slated first for diesel engines with gasoline units to follow, succeeds the integrated starter/alternator-equipped Citroën C3 and C2 models with automatic engine stop/start, which were launched in 2004.

The e-HDi system architecture includes a 70-Ah sealed lead acid battery and a Valeo-sourced integrated starter/alternator rated at 2.2kW, with power electronics integrated on the back plate. It also features a Continental Automotive-sourced “e-booster” system with power electronics, whose principal component is an ultracapacitor storage device.

The e-HDi technology initially will be applied to PSA’s 1.4-L and 1.6-L common-rail diesel engines. These are used extensively across Peugeot and Citroën European car and light CV ranges, as well as by Ford, Mazda, and Volvo, although it is not clear at this stage if the technology will be made available to these other manufacturers.

Modifications to the diesel engines include a revised turbocharger lubrication system, a reinforced fuel injection pump and crankshaft bearings, and a reinforced dual mass flywheel.

The alternator voltage-control system provides regenerative charging to the battery when the driver lifts off the accelerator. The e-booster system, rated at 600 Farad/5V, draws power from the electrical network.

Effectively, the e-booster acts as a buffer for the electrical system. Its principal functions are to provide electrical boost power to drive the starter/alternator for engine restarting and also to provide support power for the electrical system at engine start-up. The arrangement uses the conventional starter motor, which will be fitted in all cases.

The system always employs the starter motor for the first start of the day, and when the ambient temperature falls outside the operating envelope of the alternator/starter system (-5˚C to +30˚C).

The additional voltage from the e-booster would ensure successful restarting even if the battery is partially discharged. When starting, the battery and e-booster are connected in series.

PSA engineers reason that the e-booster overcomes the need for a 100-Ah battery, which would be needed to restart diesel engines of up to 2.0-L displacement. A lead-acid battery that size would have to be fitted in the trunk of many Peugeot and Citroën models and would add more to vehicle weight.

The e-booster also provides support power when the internal-combustion engine is switched off by the auto stop/start system, to drive systems such as the power steering. During a start cycle, PSA claims that the e-booster charge drops by around 0.5 V. Since it is recharged at the rate of around 1 V per 10 sec, it takes around 5 sec for the charge to be regained. Similarly, the voltage drop is far slower than for an uncharged lead-acid battery.

PSA claims that after three months, an uncharged e-booster would still retain around 60% of its charge.

The Valeo-sourced i-StARS starter/alternator is said to be capable of some 600,000 restarts—twice as many as the starter/alternator used for the earlier Citroën C2 and C3 models, while producing 70% (53 N·m) more torque than the earlier machine. PSA engineers explain that the system was designed for central Paris traffic conditions.

For AC/DC rectification, i-StARS uses field-effect transistors in place of diodes. As a result, PSA claims efficiency of greater than 77%—better than a traditional alternator. The i-StARS machine can deliver 180 A current.

According to PSA, i-StARS is capable of starting diesel engines of up to 2.0-L displacement. Restarting is completed in 400 ms—claimed to be 30% faster compared with a restart using a reinforced starter motor similar to those used by BMW, Volvo, Kia, Fiat, Mazda, Land Rover, Toyota, or Mercedes-Benz.

With the e-HDi system active, the engine will be switched off automatically after 3 sec when inside the system’s operating temperature. The system is activated before the vehicle comes to rest. For manual transmission models, this takes place at speeds below 20 km/h (12.4 mph) once the driver has dipped the clutch pedal.

For vehicles fitted with automated manual transmission, the cutoff takes place at speeds below 8 km/h (5 mph).

The first model to be available with the system will be the Citroën C5 and C4, fitted with the 1.6 HDi diesel engine, from third quarter 2010. For this model, Citroën claims a reduction in fuel consumption in city driving of up to 15% and CO2 emissions reduced from 139 g/km to 129 g/km on the EU combined cycle. On average, PSA expects carbon dioxide emissions to be reduced by around 5%.

The system progressively will be available for other PSA models fitted with 1.4 and 1.6 HDi diesel engines between late 2010 and 2013. The company expects that 30% of its HDi diesels will be fitted with the system by 2012 and has set a target of 1 million e-HDi-equipped models to be sold by 2013.

PSA will then make the system available on gasoline-powered models later. According to Jean-Marc Gales, Executive Vice President, Brands, e-HDi will add “a few hundred euros” to the sticker price of a vehicle.

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