Plugging in to More Efficient Hybrids

Since hybrids hit the U.S. market six years ago, the misconception that the cars must be plugged in and charged has been pervasive. It's an understandable conclusion: Electric car plus gas car equals car with fuel tank and power cord.

In truth, automakers determined years ago through market research that consumers overwhelmingly saw plugging one's car into a wall outlet as a drawback and a disincentive to buying a hybrid. As a result, hybrids don't have power cords, and automakers have labored to educate consumers of this fact. But as gas prices hover comfortably around the $3-per-gallon mark, plugging in is beginning to look like a good idea to consumers and automakers alike.

Plug-in Charging: The Hybrid's Running Start

So where does the charge come from in a normal hybrid? It comes in part from its ability to capture energy that is lost when a conventional car coasts or brakes. The car's momentum turns the hybrid's electric motor, which serves in this case as a generator, charging the high-voltage battery pack.

This stored power is then used to assist the gas engine in accelerating the car again. In the real world, momentum can't keep the battery fully charged, so the engine often must drive the generator and charge the battery. Naturally, this burns gas. So charging the battery with household voltage ahead of time is like giving the car a running start. More battery capacity, which is necessary for a plug-in hybrid, simply means the running start lasts longer. If nothing else, it saves significant fuel in short trips, especially in city driving.

Aside from Honda's and Saturn's, which operate differently, all current hybrids can run on battery power alone for brief spurts. Actually, spurt suggests speed; it's more of a mosey. To accelerate at a normal rate, you have to push the accelerator far enough that the gas engine kicks in. In my experience, hybrids accelerate far less than expected on battery power alone, but shut down the gas engine with surprising frequency when coasting and braking.

Pioneers Aren't Waiting for Automakers

A hybrid can charge its high-voltage battery pack through regenerative braking, a process that captures otherwise-lost kinetic energy.

By modifying their Toyota Priuses, some enterprising owners have increased their fuel economy to as much as 100 mpg for the first 50 miles. (After that distance, the overnight charge is depleted and the hybrid returns to its already respectable gas mileage.) Doing this has required the addition of not just a 110-volt household power cord but more battery capacity.

Obviously, most owners who plug in their hybrids overnight are engineers or other technically adept types whose modifications are major and too dangerous for laypersons. Also, the word "violate" seems too mild to describe what these changes do to the factory warranty. As for the cost excluding labor, we're talking a few thousand bucks.

Two companies plan to do the work for you. A company called EDrive has developed a retrofit to juice up 2004 and later-model Priuses and is testing prototypes with California's South Coast Air Quality Management District, the government body that regulates air pollution in the Los Angeles region. The company plans to market the upgrade to the public for less than $12,000 installed. Hymotion, a Canadian company, is likewise retrofitting Priuses and Ford Escape and Mercury Mariner SUVs for fleet use, and is developing similar hardware for other Lexus and Toyota models. Its target price for the Prius upgrade will be $9,500 installed when it's offered to the public in October.

Even with the claimed doubling of fuel economy, these systems are unlikely to pay for themselves and will probably appeal only to the type of enthusiasts who adopted hybrids early on. For mass-market acceptance, it will have to be affordable and/or save the driver money in the long run — and the short or medium run would be better. This will be up to the automakers.

Batteries — and Power Cord — Included

DaimlerChrysler is testing plug-in hybrid technology on a commercial van.

Despite past efforts to market unplugged hybrids, automakers are now thinking twice. DaimlerChrysler — the parent company of Mercedes-Benz, Chrysler, Dodge and Jeep — has built plug-in prototypes using its commercial van. Toyota, the hybrid leader, is expected to offer plug-in capability in a next-generation Prius. Other manufacturers are keeping similar efforts under wraps.

The reason automakers need time to roll out this functionality is that their current hybrid models' batteries simply don't have enough capacity to increase the electric motor's role. One could argue that today's most efficient hybrids are one-half electric and one-half gas. The others are weighted more heavily toward gas. Hybrids that run strictly as electric cars until their battery is depleted would need to have more powerful motors and batteries — basically to swing the balance further in the electric direction.

The notion of a plug-in hybrid that's completely electric until the charge runs out is another common misconception. Current hybrids aren't powerful enough to satisfy the average motorist when running in electric-only mode. The motors and batteries required to change this would be heavier and at least somewhat larger, which eats into gas mileage gains and can require more extensive modifications elsewhere in the vehicle. (Think interior space, braking power, etc.)

So future plug-ins are likely to feature incrementally more robust motor output and more battery capacity that continue to work in concert with the gas engine. The car will accelerate more quickly without starting the gas engine, and probably will stay in electric-only mode to higher speeds than hybrids now do (about 30 - 35 mph). It's all about the electric aspect assisting the engine more than it does now, with the most efficiency gains in the low-speed and stop-and-go driving conditions in which hybrids already excel.

What's the Benefit of All This?

Hybrid vehicles, such as the Toyota Prius, emit fewer smog-causing pollutants than conventional vehicles.

Put simply, the advantage to plug-in hybrids is less gasoline burned, and all the advantages that come with that, including a proportional decrease in the greenhouse gas carbon dioxide, and lower pollution emissions — at the car. Wha? Remember that electricity comes from somewhere. It's neither free nor pollution-free, if we're talking about the electric grid, which I am. (Renewable sources are ideal, but let's stick to worst-case scenarios here.)

U.S. electricity comes mainly from coal, natural gas and nukes, all of which have environmental shortfalls. But even if you consider the life cycle of battery-electric car power versus gasoline power, the decrease in CO2 per mile is roughly 46 - 61 percent, according to the U.S. Department of Energy.

While power companies have their own environmental problems, there's value in the fact that hybrids decrease emissions where they drive, lessening the impact on smog-prone metropolitan areas.

Proponents also claim that electric cars operate at the equivalent of less than $1-per-gallon gasoline, though the results are far less clear when discussing vehicles in which gasoline supplements rather than replaces the electricity. Issues of distance driven per charge and the vehicle's gas mileage further complicate the calculations. While the amount is in question, there appears to be consensus among researchers that plug-in hybrids cost significantly less to operate, even when they get their charge from the public utility.

The simplest calculation is how the plug-in hybrid affects foreign oil imports: The less petroleum a car uses, well, the less it uses. Despite their other ills, the coal, natural gas and nuclear energies that feed the grid come from North America. If pollution and cost are your biggest concerns, the entire energy sector has plenty of work to do, and an environment of uncontestable advantages among alternative fuels always seems to be months or years in the future. But if the goal is to use less imported oil, the impact of biofuels and electric drivetrains is dramatic, and they provide it today.