MILD-HYBRIDS AGAIN?--Carl Schwab

Mild hybrid is the term used to describe hybrid(?) schemes that in the main improve the trip mileage and performance in trip driving. The mild hybrid is a conventional car with a small electric mot/gen and a battery pack + controller and used in an "assist mode". We had a flurry of these some 10+ years ago and they faded away in favor of the PRIUS, Escape, Camry and GM-2mode type designs. This later group is marked by a LOCAL and TRIP driving mileage both good and about the same.

BER, brake energy recovery, in a mild hybrid is poor because the electric motor is too small and can't provide enough braking causing unnecessary use of the friction brakes----WASTE!

EXAMPLE OF GOOD BER: The GM IMPACT/EV1 used a 100 KW motor to provide acceleration, good, and hence also good braking, hence excellent BER.

NOTE: Torque generated as a motor is also available as torque for braking.

The newest version that GM is bringing out is its Buick LaCrosse and it is mild again. So what's the difference? Buick is not alone; Audi, BMW and others are trying this cabal again. The formula for a mild hybrid goes like this. Call it an "assist"; make the electric motor size much smaller, reduce the battery size, add a 6-speed automatic transmission combined with a smallish 4-cyclinder ICE. These cars are marked with a LOCAL mileage that is MUCH lower than the TRIP mileage. They do have excellent passing acceleration performance. As always the mild is thought to be much less costly to manufacturer than a hybrid such as the Camry. I am not sure how much success Audi has had selling its "performance/luxury" package---they charge a good deal more for it. BTW GM has had the same philosophy in marketing its 2-mode Cadillac SUV.

GM, with Buick, says they plan to make the LaCrosse only as eAsist (mild hybrid) starting in 2012. They are using an 11KW motor and small Li-ion battery to keep the weight down. They offer an E-only mode but don't push it. The 11 KW computes to 14.75 hp and the range is about 6 miles and top electric speed about 20 mph. The ICE is a 4-cylinder, Atkinson cycle, with a 6-speed automatic transmission. The 11 KW motor adds passing torque at highway speeds. Mileage is 37mpg on TRIP, but only 25mpg on
LOCAL. GM believes the combined mileage will let GM meet the upcoming Federal Standards for mileage required.

Interesting

 

Comments

[Cumberland Buick]

I am curious why the "Mild Hybrids" faded while the true hybrids like Prius gained favor? Mild hybrids sounds like a good idea; more efficiency but not a full-on hybrid for consumers who don't want to go hybrid all the way yet. Should be nice for consumers who do a lot of close-by driving in their city.

[Carl Schwab]

Reply to Cumberland Buick comment: The biggest gain is saving fuel while the car is used in near livery service i.e. daily local drives shuttling kids to and back from school. By using an aggressive electric final drive (larger electric motor)you can gain efficient regenerative braking and good BER—brake energy recovery. I think the term “mild” is more of a marketing term than anything else.

[Alexander Pummer]

some mild hybrids have beaten the real ones e.g. the BMW520 diesel/ hybrid vs. Prius competition was won by the BMW mild hybrid ,see
http://www.topspeed.com/cars/car-news/bmw-520d-beats-toyota-prius-in-fuel-economy-test-ar54284.html

[justin bieber supra shoes]

Very, very nicely done!