Conventional batteries have a low energy density. In simple terms, they weigh a lot for the amount of energy they store. A gallon of gasoline weighs 6 pounds. A battery that can hold the equivalent amount of energy weighs hundreds of pounds. That means an electric car is going to have to carry a lot of battery weight if it's going to have any kind of range.

Ordinary chemical batteries have other problems, including limited life, environmental concerns in their manufacture and disposal, high cost, and the fact that ordinary chemical batteries tend to lose power in cold weather.

Hybrid electric cars are a good interim solution to improving vehicle efficiency. I think the longer term solution will be to use fuel cells to power an electric car's motors. Fuel cells have a much higher energy density than conventional batteries and they don't have the environmental problems. Right now, they're still too expensive but the price is dropping. There are some fuel cells that incorporate a catalyst to split hydrogen from an alcohol, natural gas, or even gasoline. These would really reduce the infrastructure conversion costs.

Eventually, a pure hydrogen fuel cell would be the way to go, but finding an economical source of hydrogen is still an issue, as is the cost of the infrastructure needed to produce and distribute it. I've been wondering recently whether hydrogen production can be economically produce hydrogen at the point of sale, either by electrolysis or by splitting natural gas.