Click above for high-res gallery of the 2009 Mercedes-Benz A-Class

While Mercedes-Benz is a leader in clean diesel technology, the German luxury brand has been lagging behind its arch-rival BMW when it comes to the adoption of green technology such as stop/start in its lower-end models. This omission will soon change, as the A-Class and B-Class models, which are not sold in the U.S. market, will be granted the technology shortly. While consumers will likely appreciate the fuel savings most, the brand will be happy to report the reduction in carbon dioxide, which is regulated in most of the world.

The stop/start technology that will be used by Mercedes-Benz is a very basic system and is shared with the smart brand. Because the starter will be used much more often than normal, a larger starter motor and battery is required. BMW harnesses a portion of the energy usually lost when braking to recharge this more powerful battery. Mercedes' system does not allow this capability, though the automaker claims it is hard at work on the next-generation version of this technology which they say will incorporate regenerative braking.

[Source: Automotive News Europe - sub. req'd]

Tesla Motors has just updated their blog, this time with a post from Greg Solberg, who is Tesla Motors Firmware Engineer. The post is all about regenerative braking. Just like most of the other posts at the Tesla Motors blog, this one is quite informative and offers us all a glimpse into just what it takes to get a vehicle from the drawing board to customer hands on the road.

Regenerative braking is often a misunderstood part of electric cars. Almost everybody knows that electric cars can have regenerative braking, but most are unaware of just what is happening in the process of slowing the vehicle down. In fact, I would guess that there is a large number of drivers who don't even know what is happening when normal disk or drum brakes are slowing down their car. I think that many would find it interesting to know that much of the work going on at Tesla to make regenerative braking work properly is being done in software. The motor controller of any electric car is in charge of making the regen power recharge the batteries, just as it is in charge of making the battery charge provide forward motion. So, just as the power profile of the vehicle can be "tuned", the reverse is also true, and the braking force can be "tuned" as well. As Greg writes, there are differing opinions on how the regenerative braking should feel. Good reading, if you ask me.

Perhaps it is also worth noting that other manufacturers have worked through these same compromises already. For instance, check out Sebastian's post on riding in the Phoenix Motorcars SUT. Vectrix has done something completely new with their electric scooter, where regenerative braking occurs when the throttle is moved backwards, leaving the normal brake lever alone. There's more than one way to... you know the rest.

[Source: Tesla Motors blog]

This type of trickle-down technology makes perfect sense in the real world driving conditions that most of us encounter each and every day of our lives. Hybrids have been using regenerative braking for quite some time now as a fuel saving measure. In those applications, the electric motor or motors that help provide motive functions for the vehicle work as generators when braking force, or "drag" is applied to them, which charges the batteries. In vehicles like the new BMW 3 Series which does not use any electric motors, the alternator, which has long been used in vehicles to keep the battery charged, is selectively engaged or disengaged, and acts as both a "brake" and as a method of charging the batteries and saving gas. As a bonus, when the alternator is disengaged from the engine, the normal "drag" on the engine is eliminated, allowing for more power from the engine going to the wheels. Hooray for trickle-down hybrid technology!

Related:

• Trickle-down tech: Non-hybrid BMW 5 Series to feature regenerative braking

[Source: Motor Authority]

BMW has put up a video that does a decent job of explaining the technology that comprises their EfficientDynamics branding. The first model to get EfficientDynamics is the newly revised 120 model, which gets a start-stop system and some rudimentary regenerative braking capability. The host talks to BMW spokesman Chris Koenders at the recent Geneva Motor Show and they step through the different elements of the system.

[Source: BMW, thanks to Linton for the tip]

One of the sources of increased fuel consumption in modern cars is the parasitic loss caused by the drag of having to turn ever larger alternators to provide electrical power to all the assorted accessories and features. The alternator is typically belt driven by the engine and runs continuously, providing juice to charge the battery and drive radios, lights, computers, etc.

For 2008 BMW is introducing what they call Brake Energy Regeneration on the 5-Series. The new system uses a larger than normal battery, and an electronically controlled alternator. The alternator is disengaged from the engine during normal cruise and acceleration and activates during vehicle deceleration. This adds to the engine drag braking, and the car's kinetic energy is effectively transformed into electrical energy which replenishes the battery, which now provides the accessory power.

When the battery level gets too low, the system reverts to normal charging mode. Until BMW introduces some hybrids in the next couple of years this provides a stop gap that gives an extra efficiency boost. WorldCarFans has an animated video that shows the flow of energy around the car in various operational modes.

[Source: WorldCarFans]

Using recaptured braking power to recharge batteries has been a staple of hybrid technology since their start. BMW, a company which has not released a hybrid model as of yet, plans to put into production a new type of alternator in their newest 5 series models which will recharge the battery in the car under braking. The system also includes a new type of lead-acid battery that can take the extra quick blast of electricity in stride.

BMW plans to improve the efficiency of all their cars shortly as part of their Efficient Dynamics Program. The program will focus on improving efficiency in areas such as aerodynamics, tire technology and engine stop/start features. Expect to see systems such as these and the regenerative braking on other BMW models shortly.

[Source: Fifth Gear via Jalopnik]