Ever wondered why gas is the energy source of choice for the world? Design News, an industry magazine for engineers, recently had an article about what it's going to take to convert to electricity based automotive systems.

Based on some industry experts, they estimated the energy density of lead acid batteries, Li ion batteries and gasoline.

Lead acid = 50 W-Hr/kg
Li Ion = 150 W-Hr/kg
Gasoline = 12700 W-hr/kg

Gasoline has 250 times the energy density of a lead acid battery.

Keep in mind that IC engines aren't that efficient, but even if only 3500 W-Hr/kg are available that's still a huge disparity in energy.

What this means is a lead acid battery that is comparable to a tank of gasoline will need to be 70 times heavier than gas. A Li-Ion battery will be 23 times heavier than a tank of gas. Kinda explains why electrical cars aren't that popular, huh.

Beyond the energy requirements, there's also cost of the batteries and the recharge time. Cost is the reason why the plug in hybrids around the corner only have a range of 30-40 miles before the engine has to kick in. Battery technology is just not at a point to provide the kind of energy needed to give higher range in a consumer level product. With a range of only 30-40 miles (maybe extended to 100 miles?) and a recharge time of 6 hours, one can see why pure electric vehicles are not a viable option for the majority of consumers.

I have no doubt that in the future we'll be seeing vastly improved mpg or even some other technology like hydraulic hybrids, but it'll take time.