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GM’s eAssist seeks to provide a cost-effective solution for improving fuel efficiency and driving dynamics

15 December 2011

Eassist
The components of the Malibu Eco eAssist system. The 15 kW motor generator is only slightly larger than current alternators, which, for this segment, would be about 2 kW. Click to enlarge.

General Motors is exploring the use of its light electrification system eAssist as a cost-effective means to improve both vehicle efficiency as well as driving dynamics. Initially introduced in the Buick line, eAssist has now made the jump to the Chevrolet line with its application in the new Malibu Eco (earlier post)—which will be the only version of the new Malibu initially available.

The eAssist applied in the Malibu, while not a “second-generation” of the eAssist in the sense of a new design, represents a substantive rebuild with improved components over earlier efforts, according to Daryl Wilson, eAssist Lead Development Engineer. Wilson and other members of the Malibu engineering team presented at a Malibu Eco media event.

The eAssist system consists of:

  • A 32-cell, 115V, 0.5-kW Li-ion battery pack (15 kW peak power) using cylindrical power-optimized cells from Hitachi. The power electronics and the pack are packaged in the “eAssist power pack” which includes the batteries (2 parallel 16-cell modules) and the power electronics, both of which are air-cooled.

  • An electric motor-generator that provides 15 kW of maximum generating power @ 1570-3180 rpm; 110 lb-ft (150 N·m) maximum electric motor torque (cranking); 79 lb-ft (107 N·m) maximum electric motor torque @ 1,000 rpm (electric assist); and 15 hp (11.2 kW) @ 1,000-2,200 rpm maximum electric motor power (electric assist). The motor generator is liquid-cooled.

The system’s electric motor-generator is mounted to an Ecotec 2.4L four-cylinder engine, in place of the alternator, to provide both motor assist and electric-generating functions through a revised engine belt-drive system.

The key to the eAssist system is the ability to capture energy that would otherwise be lost and utilize that energy to optimize the efficiency of the vehicle in many different ways.

—Daryl Wilson

The business key for GM on this particular system was to define the performance parameters in such a way as to deliver benefits, but without encroaching into higher cost component requirements.

As an example, Wilson said, the eAssist system captures up to 15 kW of power during deceleration or braking. A system that captured more than 15 kW from brake regen would have required a more complex, costlier braking system as well.

eAssist supports the Malibu Eco in four main ways, Wilson said:

  • Auto Stop. The stop/start function enabled by eAssist is seamlessly integrated into the Malibu, with very smooth engine stops and restarts. The only indication for a driver that the engine has come back on is the engine noise, and the indicators on the information screen.

  • Up to 15 hp of electric assist. GM uses that power to put the engine into a more efficient operating position in most driving and to support a lower final drive ratio allowing the engine to run at low rpm at a high load point. (As an example, on a test drive of a Malibu Eco during the media event, the engine was running at about 1500 rpm at about 60 mph on level terrain.)

    While it’s possible to configure any car to run like that, Wilson said, you give up on driving dynamics. The extra power from eAssist offsets those losses. The new Malibu Eco is faster than the current Malibu, and the reserve acceleration form eAssist provides ample support for acceleration, grades and overtaking.

    There is, however, no electric “creep” function with eAssist; i.e., when in traffic, and the driver lifts his or her foot from the brake, but does not press the accelerator, the engine still kicks in to power the creep. The reason for that, Wilson pointed out, is that because the eAssist system is, by its design, connected to the crankshaft, it would have to drag the engine along with it when creeping. Given that, it is more efficient to have the engine come back on.

  • Stored energy in the battery pack offsets use of fuel otherwise consumed to run an alternator for charging for the radio, fans, lights, etc.

  • Very aggressive use of deceleration fuel cutoff.

The 2013 Malibu Eco achieves 12% greater highway fuel economy than current models equipped with the 2.4L engine; GM estimates fuel economy of 25 mpg US city, 37 mpg US highway, 29 mpg US combined (9.4, 6.4 and 8.1 liters per 100 km, respectively).

December 15, 2011 in Engines, Fuel Efficiency, Hybrids, Vehicle Systems | Permalink | Comments (28) | TrackBack (0)

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Comments

Nice tack-on, but why same price as a 8 mpg better Sonata hybrid at the same price?

Better off yet, buy a new 2012 Toyota Camry Hybrid.

GM is not marketing this as a hybrid, there is no hybrid label anywhere.. is just a different configuration of the alternator and starter :)

In the Regal, eAssist is a $2k option.. in the Canadian LaCrosse it is (about) a $1000 option.. so we know its not costing GM much.

It is a cost effective addition that could go on several models with this engine. Considering the mileage improvement versus the cost increase, it might appeal to some buyers.

Seems like a great Idea, consumers might actaully like it.

This plus some small improvements in other areas, is all that is required to achieve the 2020 CAFE standards, and at million- unit scale this probably less than $1000 to the customer. For example, add this to a Cruze Eco, and you would get ~32city/48 hwy. Add it to a Ford Fiesta and you get ~35/48. Add it to a Ford Focus diesel (yes, there will be one) and you will get ~45/58. Better yet, add it to a Ford F-150 with the Ecoboost 2.0L and you will get ~24/32 with no drop in power. That's what people don't understand: the new CAFE standards are based on current technology. It just has to be deployed.

Yes Dollared, CAFE is what was achievable 10+ years ago. This type of very mild hybridization is just enough to meet current CAFE. They will have to do much better in the near future. Current Prius III already meet 2025 CAFE. Prius (2025) will probably meet CAFE 2040?

What shall we understand here?

We need to understand that everyone is not going to buy an EV so we need to offer something that is affordable and reduces oil imports.

SJC, true not everyone will buy an EV and these small measures will help somewhat. But with recent developments in Li-ion materials, $100/kWh batteries are looking possible well within the decade. So a 25kWh battery may be the most expensive single component in an entry level EV. Which suggests that $12-14k econoEVs are plausible.

In that case with electricity costs plummeting, we can expect the cheapest car on the lot is an EV. Even with Level 3 charging there will still be a delay compared to liquid fuels - but driving habits show home charging will cover 85-90% typical drive patterns.

So, unless you cannot charge at home or work - ICE would be the more EXPENSIVE choice for light duty transport. Add to that disincentive taxes on fuel and ICE - the EV is the most cost effective transport.

Reel$$, the fleet replacement rate states that even if we stopped all ICE engine cars tomorrow, it would be 15 years before they reach 80% of the fleet. Of course, we don't ahve the supply capacity to build that many electric cars. And we would have to build 100 coal plants to charge them.

We need immediately deployable technologies that cut petroleum usage now. This one is great - cheap and instant 12% increase in mileage with no other penalty. And these uses of electrification establish a step function that leads to a majority electric fleet in 40 years. If you don't understand that that is the fastest possible adoption curve, you are not good at arithmetic.

eAssist will improve and get cheaper as the tech advances.. I would like to get rid of the belt and have it connected to the crankshaft directly... all cars need starters and alternators so why not?

Herm, you just touched on a reel issue: why not combine the starter and alternator/motor and dump one of the drive connections. This belt driven beast does the start/stop already doesn't it? Can't we dump the starter next? Maybe put the motor/alt down on the flywheel? It's a fixed drive ratio anyhow!

Dollared,

"And we would have to build 100 coal plants to charge them."

That is a silly statement. If we were going to build 100 new plants today, they would be natural gas. And with the price of solar dropping, we'd be building at least some solar by the time we got them all done.

Texas plans to build twelve more coal plants soon, so do not assume that the new plants will be natural gas.

Dollared...not one single KWh would be required if we all had or upgrade our house to German Passivhaus design and specs. Enough wasted energy at every current house could be (saved) to operate at least 3 BEVs (free).

Saving energy is 3 to 5 times cheaper than producing and consuming more and more. That is well known in many countries.

Not only it is a strong possibility but it is the best solution for USA to cut its on-going addiction to imported crude oil, huge trade deficits and very costly oil wars.

Energy is energy, by the time you burn the coal and transmit the power and get it into the batteries you are about at the same level as turning the coal into liquid fuel. There is no nirvana and no free lunch.

SJC...build or upgrade your house to German Passivhaus Institute standards and you will save enough energy to operate 3+ BEVs.

Saving energy by 1001 existing available ways may be the best and quickest solution for USA (and many other places). Using less energy is much cheaper, healthier and wiser than producing and using more of it.

Please do not tell that to right wing politicians. They will find a way to make it anti-American.

"Energy is energy, by the time you burn the coal and transmit the power and get it into the batteries you are about at the same level as turning the coal into liquid fuel."

I'd like to see supporting data for that, but in any case you left out a major part of the equation, the inefficiency of an ICE compared to an electric drive train. Even if you are at the same energy level by the time you get the fuel into the vehicle, which I doubt, you then throw away about 80% of it in an ICE vs 15% of it in an EV.

Coal to electricity 30%, transmission loss 10%, charger loss 10%, battery loss 10%, controller loss 10%, motor loss 10%.... you end up slightly more efficient than turning the coal into diesel and running it in a TDI.

What nobody wants to acknowledge are the DOE studies showing USA overnight spinning reserve capacity enough to charge 100M light duty EVs with an average 40kWh battery.

No one needs to build more power plants to charge EVs provided the majority charge at night.

Electrical energy is becoming ever more abundant, cheaper, from ever-cleaner sources - as you all know.

And sorry Harvey, but the USA follows LEEDS standards for eco-building. German Passivhaus may be efficient but then, so was the Third Reich.

the fleet replacement rate states that even if we stopped all ICE engine cars tomorrow, it would be 15 years before they reach 80% of the fleet.
Half of total fleet mileage is driven by vehicles under about 6 years old. 50% of the problem gone in 6 years, and probably 75% in 12.

Pairing an 11 kW motor on each rear wheel with a bigger battery makes a serviceable PHEV. That might only cut fuel requirements 50% for the first generation, but 25% of demand cut in 6 years is 4%/yr, or roughly the worst-case decline rate of world oil production.

Coal to electricity 30%, transmission loss 10%, charger loss 10%, battery loss 10%, controller loss 10%, motor loss 10%.... you end up slightly more efficient than turning the coal into diesel and running it in a TDI.
Way off. Grid transmission losses are typically less than 10%, lithium batteries charge at 98% efficiency, chargers can be between 90-95% efficient, controller/motor combinations are closer to 90% efficient than the 80% you suggest.
I'd also like to see your data for the efficiency of coal to liquids processes. How much grid electricity is used per gallon for example?

believe what ever you want, I don't care.

REEL$$....LEEDS + CAFE = 75% wasted energy. Prius HEV + Passivhaus Institute standards = 75% energy savings. That's a major difference?

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