San Diego Union-Tribune (Sunday)
A great idea, 50 years too late
Dear Car Talk:
Are electric cars rigged up to recharge as they drive? It seems like there could be some sort of alternator set up on the wheels to generate power that could extend the range of the battery.
Alternatively, are any set up with a reserve battery — akin to a spare gas tank like some trucks have?
— John
This is a brilliant idea, John. You’ve just invented regenerative braking.
You’re about 50 years too late to make any money on it in cars, but good thinking, nonetheless.
Both hybrids and battery-electric vehicles use regenerative braking.
When the driver wants to slow the car and taps on the brake pedal, the first thing that happens is that a generator is engaged.
The wheels then turn the generator, simultaneously charging the battery, and — because it takes effort to spin the generator — slowing down the car.
If the stop is gradual enough, the car can be brought to a complete halt using the regenerative braking. In that case, the maximum amount of kinetic energy is recouped and put back into the battery.
If more stopping power is needed — the computer adds in the friction brakes (the brake pads) to stop the car safely, but then some of that energy is lost to heat.
You’ll be happy to hear that your other idea, John, the spare battery, has not been applied to cars. But you’ll be unhappy to hear that it may never be.
A spare battery simply weighs too much to lug around. It would reduce the range of the car considerably. You’d need a trailer to pull it around. Then you’d need a spare battery for the spare battery.
In fact, it’s so unworkable that, in the early days of electric cars, some manufacturers added small gasoline engines as backup chargers rather than have to add the weight of more batteries. That tells you how badly they wanted to avoid adding another battery.
So, if you can invent a spare battery that weighs about the same as a spare tire, write back immediately.
Post questions online at Cartalk.com.