Mazda reveals its first regenerative braking system

MAZDA has revealed details of its first regenerative braking system, which will debut in the next-generation Mazda6-previewing Takeri concept at next week’s Tokyo motor show and has been confirmed to appear in the first production models next year.

The all-new CX-5 compact SUV, due on sale here in early 2012, is the first Mazda model to combine the company’s lightweight new chassis architecture with its new range of SkyActiv direct-injection engines and latest ‘Kodo’ exterior design language.

A revolutionary new regenerative braking system has now emerged as the next phase of Mazda’s ‘building block’ strategy to reduce the fuel consumption of its new model fleet between 2008 and 2015.

Pictured in a cutaway diagram of the Takeri, the unique fuel-saving technology harnesses energy that is otherwise lost as heat during braking, but unlike similar brake energy recuperation systems, Mazda’s solution is a world-first capacitor-based regenerative braking system.

Expected to become available in either the as-yet-unseen Mazda6 replacement or existing models next year, Mazda says its ground-breaking ‘i-ELOOP’ is the world’s first passenger vehicle regenerative braking system to employ a capacitor - an electrical component that temporarily stores large volumes of electricity.

Left: i-ELOOP capactitor-based regenerative braking system.

It claims i-ELOOP can reduce real-world fuel consumption by about 10 per cent in stop-start driving conditions, meaning it will have a greater contribution to efficiency than Mazda’s i-stop idle-stop function, because compared to batteries capacitors can be charged and discharged rapidly and are resistant to deterioration through prolonged use.

Conventional regenerative braking systems now seen on a wide variety of new cars typically use an electric motor or alternator to generate electricity as the vehicle decelerates, thereby recovering a portion of the vehicle’s kinetic energy, while regenerative braking systems in hybrid vehicles generally use a large electric motor and dedicated battery.

However, Mazda says close examination of vehicle acceleration and deceleration mechanisms led it to develop a system that rapidly recovers a large amount of electricity every time the vehicle slows down and, unlike hybrids, avoids the need for a dedicated electric motor and battery.

As with similar systems, i-ELOOP converts kinetic energy produced by the vehicle as it slows down into electricity to power climate, audio and other electrical systems, thereby reducing load on the engine to do so.

I-ELOOP combines a new 12-25-volt variable-voltage alternator, a low-resistance electric double-layer capacitor (EDLC) and a DC/DC converter to recover kinetic energy as soon as the driver lifts off the accelerator pedal.

The variable-voltage alternator generates 25-volt electricity that is stored in the capacitor, which was specially developed for vehicle use and can be fully charged in seconds. The DC/DC converter steps down the electricity to 12 volts before it is distributed directly to the vehicle’s electrical components, including the battery as required.

It also works in conjunction with Mazda’s the idle-stop function, which debuted alongside the SkyActiv 2.0-litre petrol engine in Australia’s Mazda3 SP20 in October, to extend the period that the engine can be shut off.

Combined with the CX-5’s new SkyActiv 2.2-litre clean-diesel engine, which is also matched with a (new six-speed) automatic transmission for the first time, i-ELOOP is expected to reduce the next Mazda6’s fuel consumption to as little as 4.2L/100km.