Dear Car Talk:
I am very interested in electric vehicles, but I am concerned about their range. Why can't there be a charging system on board that continuously charges the battery? All that would be needed is a small gas-powered motor to operate an alternator.
I understand that the Chevrolet Volt comes close to this kind of system, but at a certain speed there is a gas-powered motor that will also send power to the wheels. So the Volt is not 100 percent electric but a form of a hybrid. -- George
The Volt is pretty close to what you're talking about, George. And it works wonderfully. The car gets 50-plus miles on electricity alone. That's enough to cover the daily driving for a huge percentage of our population. And if you need to go farther than that before recharging, the gasoline engine comes on and makes more electricity.
You're right that the gasoline engine can also contribute to propulsion when needed (like when climbing a hill or passing), but we don't see that as a downside.
However, if you want the exact system you describe (called a "series-hybrid"), then you want a BMW i3 with what they call a Range Extender. The Range Extender is a two cylinder gasoline engine that kicks in when you run out of battery power, and provides electricity to get you another 65 miles or so.
Personally, I'd take the Volt. The total range of the BMW i3, even with the extender, is only 180 miles. The Volt can go 420 miles with both its battery and gas tank full.
Of course, the hope (and we're starting to see the reality already) is that electric cars will eventually have the range of our current gasoline cars. We're already seeing electric car ranges of over 200 miles (Tesla, Chevy Bolt, Jaguar I-PACE). And as batteries improve and recharging gets faster, that range should get even longer, and you won't need no stinkin' gasoline engine at all, George.
But in the meantime, if you want to be a series-hybrid purist, buy an i3. If you want to worry less about range and save $5K-$15K on the purchase price, buy a Volt.