Hybrid Electric Vehicle

Governments have been trying to reduce fuel consumption and lower pollution without imposing drastic change on the driving habits of the motorist, and the hybrid car fits the bill well, especially in large cities. So strong is the acceptance on the political scene that the move has crossed the Atlantic. Germany and France, with their fuel-efficient and clean-running diesel engines, are showing a good face by adding hybrid versions to their lines of cars. However, a visit to the auto show in Frankfurt in 2009 proved that muscle cars still attract the largest crowds, while vehicles with a low carbon footprint sat neglected on the show floor. 

Batteries play an important role in electric powertrains, and the price per kilowatt-hour varies according to battery type. Table 1 lists typical batteries for mobility. At $120 per kWh, a deep-cycle battery for golf cars is most economical, followed by starter and forklift batteries. Complex manufacturing, rare raw materials, electronic safety circuits and management systems make newer technologies more expensive than older systems. High-volume production will moderate the price only marginally. Batteries for powertrains are about $1,000 per kWh.

The electric vehicle will tell how far the battery can go, and we hope for success. Advancing further and deploying batteries for heavy trains, large ships and passenger airplanes makes little sense today. Current battery technologies are not yet suited to replace petroleum; the NCV of a battery is low, the price is high and the life span short. Finding a new energy source comparable to petroleum products will be difficult to find.

Application

Chemistry

Capacity

Cost/kWh

Battery price

E-bicycle*

Starter

Golf car

Forklift

Stationary

HEV

PHEV

EV

Nickel, Li-ion

Lead acid

Lead acid

Lead acid

Lead acid

NiMH, Li-ion

NiMH, Li-ion

NiMH, Li-ion

360W

0.5 to 1kWh

8kWh

18kWh

Small to large

1 to 2kWh

5 to 15kWh

20 to 40kWh

$1,200

$160

$120

$166

$200–300

$1,500

$1,100

$750

$400-500

$120

$720

$3,000

Size dependent

$2,000–3,000

$10,000–12,000

$15,000–30,000

Table 1: Battery sizes of wheeled mobility
The estimated cost/kWh is lowest with lead acid and most expensive with lithium-ion.

*   The e-bike only compares nickel- and lithium-based batteries used in the West.

Development of the Hybrid Vehicle

Propulsion by an electric powertrain is not new — Ferdinand Porsche designed a hybrid vehicle in 1898. Called the Lohner-Porsche carriage, the hybrid function served as an electrical transmission rather than power boost, which is the primary purpose of the current hybrids. With Mr. Porsche in the driver’s seat, the car broke several speed records in Austria, including a record set at the Exelberg Rally in 1901.

Another example of an early hybrid was the 1915 Woods Motor Vehicle built in Chicago. It used a four-cylinder internal combustion engine in conjunction with an electric motor. Below 25km/h (15mph) the electric motor propelled the vehicle, and at higher speeds the gasoline engine kicked in to take the vehicle up to a top velocity of 55km/h (35mph). As part of the Federal Clean Car Incentive Program, Victor Wouk installed a hybrid powertrain in a 1972 GM Buick Skylark, but the EPA (US Environmental Protection Agency) canceled the program in 1976. Meanwhile, Honda and Toyota made headway by commercializing fuel efficient hybrid cars.

The purpose of the modern hybrid electric vehicle (HEV) is to conserve fuel without sacrificing performance, and the HEV achieves this by using an electric motor to assist the internal combustion (IC) engine on acceleration and harness kinetic energy when braking. The IC engine turns off at a traffic light and the electric motor propels the car through slow-moving traffic. This saves 10–12 percent in fuel, reduces pollution and lowers the noise level. On full power, both the IC and electric motors engage simultaneously for optimal acceleration.

The hybrid power sharing has advantages in that the car can be fitted with a smaller IC engine, which can be tuned for maximum fuel efficiency rather than high torque. This marriage works well because an electric motor of the same horsepower has better torque for acceleration than the sluggish IC engine. The IC engine works best for highway cruising.

The HEV uses a mechanical powertrain to transfer power from the IC engine to the wheels, and in this respect the HEV resembles an ordinary vehicle with a crankshaft and a clutch. The difference is the sharing of the propulsion with the electric motor. This type of hybrid is known as parallel configuration. Early models ran on lead acid, but these batteries were too heavy. Today, Honda and Toyota use nickel-metal-hydride and are gradually switching to lithium-ion. Besides higher capacities, Li-ion is easier to charge and has a lower self-discharge than NiMH, but the batteries are substantially more expensive.

The HEV battery consists of cylindrical or prismatic cells connected in series to attain several hundred volts. Airflow around the cells provides cooling, and many designs use cabin air to keep the battery at a moderate temperature while driving. The warm air heats the battery when cold, and air-conditioned air keeps it cool in warm climates. To improve temperature control, some batteries use liquid coolants. Figure 2 shows a demonstration pack of an early Toyota hybrid car battery that is air-cooled.

Nickel-metal-hydride battery

 

 

Figure 2: Nickel-metal-hydride battery

The air-cooled battery is installed behind the back seat.

Courtesy of Toyota Museum, Nagaya, Japan

 


Battery longevity is a critical requirement for a hybrid car. While a 3- to 5-year battery life is acceptable in a consumer product, such short service would pose a major drawback for a hybrid battery costing $2,000–3,000. Battery replacement would constitute an expense comparable to
a motor or transmission overhaul.

Most batteries for HEVs are guaranteed for eight years. To meet this long service life, the cells are optimized for longevity rather than small size and low weight, as is the case with portable consumer products. The battery manufacturers achieve this in part by using a thicker and more durable separator. To reduce stress, the battery operates in the 20–80 percent state-of-charge bandwidth, or roughly 3.5– 4.0V/cell for Li-ion, rather than the customary 4.20V/cell.

HEV batteries avoid deep discharges and in many ways operate similarly to a starter battery by applying short power bursts for acceleration rather than long, continuous discharges. Rarely will an HEV battery discharge to a low 20 percent state-of-charge (SoC). Under normal use, a parallel HEV consumes less than two percent of the available battery capacity per mile (1.6km). Capacity fade can go unnoticed, and an HEV battery will still work well with less than half the original capacity.

Figure 3 shows the battery capacity of six hybrid cars at a 256,000km (160,000 mile) end of life. The US Department of Energy’s FreedomCAR & Vehicle Technologies Program (FCVT) performed the test in 2006 according to SAE J1634 recommended practices. It includedthe Honda Civic, Honda Insight and Toyota Prius. The hybrid battery of the two Honda Civic vehicles had 68 percent remaining capacity; the Insight had 85 percent and the Prius 39 percent. Even with lower capacity, the fuel efficiency was not severely affected. The Insight showed a 1.2mpg (0.12L/km) decrease in fuel economy during the test, while the Prius reduced the fuel efficiency by 3.2 mpg (0.33L/km). The air-conditioning was turned off in both cases.

End-of-life battery capacityof HEVs

Figure 3: End-of-life battery capacityof HEVs
At 256,000km (160,000 miles), the two Honda Civic vehicles had 68% capacity, the Insight 85% and the Prius 39%. The capacity fade did not affect the fuel efficiency by much.

Courtesy of FreedomCAR & Vehicle Technologies Program

Paradox of the Hybrid Vehicle

As good as a hybrid may be, the car is not without paradoxes. At a conference addressing advanced automotive batteries, an HEV opponent challenged a maker of HEV vehicles by saying that a diesel car has better fuel economy than a hybrid. Being a trained salesman, the HEV manufacturer flatly denied the claim. Who is right? Perhaps both. On the highway, the diesel car is clearly more fuel-efficient but the HEV has better fuel economy in city driving. Harnessing regenerative braking and accelerating with a high-torque electric motor offers advantages that the German diesel cannot provide. Combining the two would provide the best solution, but low fuel prices do not justify the high cost of a diesel-hybrid.

Someone asked further: “What would happen if the HEV depletes the battery while driving up a long mountain pass? Will the car have enough power with the small IC engine?” “Yes,” the respondent replied. “The car would make it without batteries but would have marginal power to maneuver.”

To compensate for this eventuality, some HEV manufacturers offer SUVs featuring a full-sized IC engine of 250hp and an electrical motor of 150hp — 400hp in total. Such vehicles will surely find buyers, especially if the government provides grant money for being “green.” It’s unfortunate that consumers purchasing small cars or taking public transportation won’t qualify for such a generous handout.

Wolfgang Hatz, the head of powertrain for Volkswagen Group, said that hybrid technology is a very expensive way to save a small amount of fuel and states that Volkswagen only makes hybrids because of political pressure. Hatz argues that Toyota would have a problem producing the hybrid cars in high volumes and points out that the automotive industry would go bankrupt if all cars needed to be hybrid. Hatz supports the modern diesel as the most energy-efficient motor, especially on highways. 

Hybrids are socially acceptable and governments support them with subsidies because they don’t impose a lifestyle change for the voters. But simply making an SUV a hybrid by adding batteries and an electric powertrain does not provide a lasting solution to the dwindling oil supply. Driving a two-ton vehicle eats up precious resources, even if part of the 400hp propulsion system comes from a “clean” motor. Common sense reminds us that we should go back to lighter vehicles with a fraction of the horsepower of present monsters.

Volkswagen may have a solution — the 1-liter Car (Figure 4). It is so called because the concept vehicle burns only one liter of fuel per 100km. To prove the concept, VW chairman Dr. Ferdinand Piëch drove the car from their headquarters in Wolfsburg to Hamburg, Germany, for a shareholders meeting. He averaged just 0.89 liters per 100km (317mpg) along the way.

Volkswagen’s 1-liter Car

 

Figure 4:
Volkswagen’s 1-liter Car

The 1-liter Car is said to be the most economical car in the world. VW plans limited production of a hybrid-based 1-liter car by 2013.

Courtesy of Volkswagen AG

Aerodynamics and weight are key to low fuel consumption. While a typical car has a drag coefficient of 0.30, the 1-liter car comes in at only 0.16. Carbon fiber and a magnesium frame reduce the weight to 290kg (640lb). The one-cylinder diesel engine generates 8.5hp (6.3kW) and the 6.5-litre (1.43 gallon) fuel tank has a range of 650 kilometers (400 miles) at an average fuel consumption of 0.99 liter per 100km (238mpg). In 2013, the second edition L1 based on a hybrid system will go into limited production. Even if fuel prices were to increase ten-fold, this car would still provide economical transportation, and without government subsidy. 

Comments

On March 15, 2011 at 8:57pm
Alan wrote:

At 24 MPG, $3.50 a gallon of gas, (on March 2011), this cost will increase and 150,000 miles, the cost of gas is $21,875.  At 48 MPG (Prius) the extra cost for a hybrid must be less than $11,000. Which it is for most competitive powered cars.  The batteries cost is around this savings, since the electricity charging cost is a small fraction of the gas costs.
The hybrids have a future.

On April 19, 2011 at 7:11pm
Mark Smith wrote:

hybrids are true cars they give us good cars with pollution free vehicles in this one we can have the things we wanted to a car. Hybrids have good parts and they perform in a long run they have the best cold air intake, engines, oil filter etc.

On September 5, 2011 at 4:23pm
rex wrote:

yeah mark smith is right. hybrid cars have the cutting edge technology that could lessen pollution. in addition to what you said hybrid cars have the best fuel sending unit replacement for better mileage.

On September 5, 2011 at 4:38pm
ronie wrote:

i think i read that regarding hybrid cars on the magazine. that might be the secret to hybrids fuel efficiency. but i am really not that sure if it is the fuel sending unit replacement.

On September 26, 2011 at 7:41am
Jo hn wrote:

As a two year driver of a GMC Hybrid Sierra pick-up (6L V-8) I can assure you that the driver’s habits will effect the results of the hybrid. I consistently get between 20 and 22 MPG in town and between 20 and 26 MPG on the road. I have even driven over 300 miles on one trip where I did everything I knew to get the best mileage and got 30 MPG. However, my wife, who only occasionally drives the Hybrid does not get anything near the mileage I am getting. She gets closer to what you would expect from a regular gasoline engine vehicle (14 to 16) in town. While I think Hybrids DO have a good future, it is the drivers habits that will make the largest impact with today’s technology.

On October 15, 2011 at 1:53am
flash wrote:

I’ve put 110k miles on my 08 Escape Hybrid, and in many ways I love it.  Hybrid is clearly, merely an interim solution to certain problems, but it does represent a step.  I don’t believe that battery technology is anywhere near what will be needed for even a noticeable segment of street traffic to become EV.  Hybrids do substantially alter the otherwise horrendous fuel efficiency and emissions problems with IC engines when accelerating and decelerating at rates closely linked to necessary alterations of vehicle speed.  Without regenerative braking Hybrids wouldn’t offer much.  Change to a diesel IC component would also help slightly with fuel efficiencies and emissions.  EFI, “Solid State ignition”, catalytic convertors were all added auxiliary systems added to IC engines to address those same issues.  If large societal concerns for environmental pollution and diminishing availability of petroluem like fuels didn’t exist, none of those auxiliary systems would be of any value.

Driving technique is very important with the Escape Hybrid, and Ford’s engineers could do better to address that, and I suspect will do better, once it is evident that HEV must be a stable part of their product line.

 

On April 1, 2012 at 7:08am
John Fetter wrote:

A hybrid is a very badly thought-out compromise. Internal combustion engines are horribly energy inefficient when run over a wide speed range. Efficiency improves dramatically when IC engines are designed to run at fixed speed, constant power output. It is pointless trying to get batteries to work an order of magnitude better than what they can achieve today.
Surely the objective is to find the most effective engineering/commercial solution?
This is my suggestion:  Engines must be redesigned from the ground up to run at fixed speed, constant power output, driving an integral generator/alternator, charging a modestly sized battery.
A single, water cooled electric motor drives the wheels. The transmission is electric. The power from the battery is regulated to drive the electric motor from standstill to full speed - as a motor to drive the car and as a generator to slow it down. Electric motors have good torque and are very efficient over a wide speed range.
Simply get in and begin driving on electric power. At, say 10 miles, the engine starts. The engine is pre-warmed by hot water from the electric motor. As soon as the engine starts, the cooling water is diverted to the radiator. When the battery reaches 80% charge, the engine is stopped. The car continues on electric power. The engine starts and stops repeatedly. It is well silenced and unobtrusive. Can go 1000 miles on a tank.
Single pedal driving. Press accelerator to speed up - keep steady to maintain speed - release to slow the car on regenerative braking. Brake pedal used to hold car at a stop and for emergencies. Absolutely brilliant. Takes five minutes to get used to and then you’re hooked for life.
Every component is used within the “comfort zone” of its engineering and commercial capability. The most efficient, most acceptable way of converting the energy that is in a fuel to driving a set of wheels. Optimum use of technology.

On May 27, 2012 at 3:22pm
JPWhite wrote:

@John Fetter

I don’t understand why the electric motor would need to be water cooled. An electric motor generates relatively little heat since it runs at 80-90% efficiency.

What you have described is a Chevy Volt.

Single pedal driving? Brilliant.

I wish the LEAF and Volt had that ability. The diminutive Mitsubishi i-Miev can be driven as a ‘single pedal’ vehicle. That little car has a future around town.

On May 27, 2012 at 4:53pm
John Fetter wrote:

JP White - The 10-20% heat given off by the electric motor can either be thrown away uselessly through air cooling, or be put to use to excellent use to pre-warm the IC engine.

What I described is not a Chevy Volt. My proposal is a liquid fuel driven vehicle with an electric transmission. An electric transmission that has an “energy memory” of 10 miles. Possibly less, not more. Relatively inexpensive lead-acid battery. This would help to prevent the catastrophic depreciation in value of pure and near-pure electric vehicles. The most likely time these vehicles are traded in is when the battery is nearly due for replacement. With a new battery costing USD15,000, these cars end up with a near-zero trade-in value.

At the fundamental level, the objective is to utilize energy from a source to propel a vehicle at the highest efficiency. This will be a liquid fuel, whether from petroleum, conventional biomass or algae. Electricity taken from the power grid in moderation - yes, but not in huge quantities. Algae looks the most promising way of converting solar into usable fuel. For the time being electricity must be coal, gas or nuclear. There is likely to be a move to algae derived fuel for all consumption in the coming fifty years. Carbon will become the most recycled material of all time.

I built an electric car in 1980. Used it constantly for everyday travel for a year, covering 10,000 kilometers. The vehicle was powered by 14 specially developed 12 volt deep cycle batteries. This experience taught me that the electric control part, that is the one pedal control, is absolutely divine but to forget about pure battery.


 

On July 6, 2012 at 1:03am
Jason Marentette wrote:

When was this created? i don’t see a time stamp

On December 7, 2013 at 8:37pm
bob wrote:

this is bogus, vw is caving to oil company pressure. they are only going to make like 400 of these cars and sell them for 150,000 US dollars.  greed drives these companies.  it wont be until we have a revolution that we will truely see these cars.
why not build a diesel hybrid that is made from ultralight materials .... so much greed and bull.

On January 11, 2014 at 4:16am
Master wrote:

We have developed solution to test Battery Pack of HEV quickly on the individual Battery Level, e.g. simultaneous capacity test of up to 38 batteries at a time . Please have a look at www.hybrids.co.nz