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Valeo Providing Stop-Start System for Mercedes A- and B-Class; Signs 1M+ Unit Deal with PSA

The StARS micro-hybrid stop-start system. Click to enlarge.

Valeo announced that its StARS micro-hybrid system equips new Mercedes-Benz A- and B-class vehicles offering that function. (Earlier post.) Valeo also recently signed a contract with PSA Peugeot Citroën to equip more than one million vehicles with its Stop-Start technology by 2011.

StARS (Starter Alternator Reversible System) cuts off the engine when the vehicle is at a standstill, at traffic lights for instance, and then restarts it quickly and silently when the driver releases the brake pedal. It provides average of fuel savings of 9%. Under conditions of congested city driving, fuel savings can reach up to 25%.

The starter alternator is driven by a belt that can also be used to drive other accessories, such as the air conditioning compressor, the water pump or the power steering. A reversible tensioner allows power to be transmitted in both directions, depending on whether the StARS starter alternator is working as a starter or a generator.

The system features a battery based on technology that accepts high numbers of charge/discharge cycles. The battery is also fitted with a sensor that enables the system to inhibit the Stop-Start function if the charge level is too low or to restart the engine if the charge level drops below a critical threshold.

The StARS starter alternator is a synchronous machine with a claw rotor. It is air-cooled and uses a three-phase current that is transformed to 12 V DC voltage by a separate electronic transformer.

In starter mode, it is capable of delivering a 600 A current generating enough torque to drive the internal combustion engine immediately and at higher revs than a conventional starter. The machine can start the engine in less than 0.4 seconds, before immediately switching to alternator mode.

In this configuration, the electronic transformer uses MOSFET field effect transistor technology to rectify the three phases. This is one of the reasons behind the 82% efficiency of the StARS starter alternator, which is a full 10 points higher than the best conventional alternators on the market. The machine delivers a current of up to 180 A.

Valeo’s micro-hybrid system already equips the Citroen C2 and C3 and the smart mhd.

Valeo is developing a supercapacitor-based extension to StARS (StARS + X) to support regenerative braking and thus enable a greater reduction in fuel consumption than is possible with the stop-start system alone.

The StARS + X system uses a slightly different architecture with different motor for starting and regen, and support for voltage between 14V and 30V. The floating voltage enables extended torque for diesel or large engine cold cranking, 4 kW generation for regenerative braking and extra power supplies for peak loads. (Earlier post.)



I think stop/start should be on all cars. However, there should be a switch to let you turn it off. There are times in the winter that you should let your car idle for a minute or two to warm up. This warming up reduces wear on vital engine parts that would otherwise lead to higher emissions.


Joseph, you're right on, this is the no brainer of the year/decade, although I doubt we'll ever see in law form - I like the override switch idea, nice. All vehicles should be E85 or B100 compatible (for future fuel source flexibility) as well. Oh...if we only had a national Voter Initiative policy to get common sense stuff like this moving here in the US.


In general, Joseph, you are right, but you have to be careful with mandates.
I assume you mean that stop-start or better should be available on all cars (say in Europe) starting 2012 or whatever.
An EU mandate could help that, and, in many cases, once it becomes common, it becomes cheap and the price goes back down.
This may well happen anyway in Europe as manufacturers struggle to hit the 130 gms CO2 limit.
But it is good news.
A million Stop-Starts will save a lot more fuel than a few thousand PHEVs.
We look forward to the electrification of transport, but this is still a positive step.


Any legislators reading this?

Please make this technology legal mandatory for all new cars. Such is the benefit to the unfortunate cyclists and pedestrians who have to breathe in the crap spewed by cars in stationary traffic.


Wow, this system looks amazingly similar to the GM mild hybrid system...


Joseph: There are times in the winter that you should let your car idle for a minute or two to warm up.

"The best way to warm up your car is to drive it."

Nickf: Any legislators reading this?

No. They are all too busy masturbating to the revenue stream reports from the gas tax, the carbon tax, and fifty-five mph tax.

In any case, do we really need another law?


"Any legislators reading this?"

Ugh. Be careful what you wish for, this could end up like the boondoggle lesislation for turning Midwest corn into profits... er, I mean ethanol.

Better legislation addresses the problem, not the solution that happens to be currently favored by influential politicos (yay corn!). Legislate in CO2 limits, exactly like what the EU is doing. Let the private sector and the capitalists figure out the best way to do it. Once they figure it out, turn in the screws a bit more.

Incremental and mass-marketable innovations like this are welcome news indeed.


Technology like this, plus Valeo's new camless variable valve timing system using magnetic actuators and electrically-actuated brakes (no power-robbing hydraulics to control the brake system!) could mean we could see 20-plus percent improvements in fuel economy in a gasoline-fuelled automobile--and that's without needing to go to the complications of direct fuel injection!


Who would've thought: turn off the engine when not needed and you save up to 20% fuel? Sort of like light switches and a lower setting on the thermostat. Well done.

Bob Bastard

Joseph, I would also like to see micro hybrid tech standard on all vehicles. I think it is probably gives the best fuel and emission savings bang for the buck, especially at high volumes. But there is no need for an override switch. Current hybrid systems already implement appropriate algorithms to keep the engine from shutting off if the engine/catalytic converter temperature or battery SOC is too low. This is a rather basic component of the design, and is necessary to meet emissions requirements.


Who said anything about new laws or mandates.

Hey Automobile makers, this means all of you.

Take the money that you would use to fight the new Cafe legislation and put it into the cars. How about putting stop-start and cylinder deactivation on all your vehicles. Both tech's have been around for a while and should be a very cheap way to improve your vehicles.

DRD T-bone


The GM BAS system doesn't shut off the engine when in park; only while in drive (as long as the A/C is not set to "yellow" which disables the stop/start function)


Another benefit is that because of the higher engine start speeds, engine wear should be reduced.

The higher engine start speeds will reduce the amount of time spent sparking the engine at low RPMs firing it up when oil flow is low. Waiting to spark the engine until it is spinning faster will allow more oil to be pumped through the engine and reduce wear on bearing surfaces.

It should also reduce fuel contamination of the oil which is also commonly caused by cold starts, possibly leading to longer oil change intervals.

It'd be interesting to find out how long you have to stop the engine to make up for the amount of energy it takes to spin it back up.

stas peterson

I'm always amazed with the people who are so prone to pass laws, requiring instant adaptation.

Your way too late in thsi case. Long before 2012 virtually all domestic and most imported autos wil have a start stop system;, probably with regenerative braking too.

All it takes is the lead time for the component supplier network to build the factories, to build the components necessary, and they are far, far, ahead of you there.


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