Green Tech

It's not every day that you get to drive an all-electric car and a brand new gas-electric hybrid. But that's just what I did last week when I took both the Electric Mini Cooper and 2010 Ford Fusion for a spin.

The two cars represent two technical approaches to gaining fuel efficiency through bigger car batteries.

Like the Toyota Prius, the newly released Ford Fusion is a gas-electric hybrid that drives primarily on the gas engine, supplemented by a nickel-metal hydride battery. By contrast, the Mini Electric, which will start to be leased to drivers next month as part of a trial, runs entirely on lithium-ion batteries, the latest battery technology.

The trade-offs of both approaches are pretty apparent. The Fusion gets over 40 miles per gallon and it's more or less like any other car you've driven: you fill it up with gasoline and it goes.

The Mini Electric, on the other hand, sacrifices the entire back seat for its battery pack. That allows it to go 100 miles on a charge--sufficient for most daily driving. But two of its advantages are that you never go to a gas station and there are no emissions from the car itself.

Meanwhile, there's yet another technology in the mix--what General Motors calls a range-extended electric vehicle or what engineers call a series hybrid (as opposed to a parallel hybrid). In that case, an internal combustion engine does nothing but charge the batteries that propel the car.

On the road
There's a lot of focus on how lithium-ion batteries are paving the way for cars with a longer range (although cost is still a serious concern). But in both the Ford and the Electric Mini, there are a number of other fuel-saving tricks at work.

The big one is regenerative braking, where the battery charges when the driver presses the brake. The Ford Fusion didn't feel very different from any other automatic transmission car. But the regenerative braking in the Electric Mini was different. When I took my foot of the accelerator, the car slowed significantly. It's noticeable but something that I got used within a few minutes of riding.

Automakers say a key component to mainstream electric car adoption is an in-board feedback system that lets drivers know how to maximize their efficiency. This is probably old hat to Prius drivers looking for ways to save on gas. But it becomes particularly important in all-electric cars, as automakers don't want drivers getting stuck with an empty battery and no place to charge.

The Ford's dashboard LCD shows when you're using the gas motor and when you're running on battery. The way to optimize for efficiency is to get to cruising speed and then tap the brakes to charge the battery, I was told. The car also has an on-dash rating system that displays a plant sprout. More leaves distinguishes the hypermilers from the lead-foots.

The Electric Mini feedback system is pretty simple: how much juice you have left is on the front dash while another meter shows whether you're drawing from or charging the battery.

How did these autos drive? For somebody with admittedly pedestrian taste in cars, I thought they both were great to drive.

If I had to pick, I'd say the Mini is more fun simply because it's a small car with a lot of pep. But then again, without a back seat to speak of, you're not going to bring your Saint Bernard to the beach in an Electric Mini.

Representatives from Ford and BMW were kind enough to hold the video camera while I drove these cars around the block in California last week and to answer my questions about what's under the hood. You can see the Ford Fusion video here and the Electric Mini video here.

Photos: Electric and hybrid cars hit the streets