In my last job, I drove an electric forklift, the battery in which—at about 3500 pounds—is heavier than most cars. I got it into my head, one day, to wonder about a comparison of that battery to gasoline.
The battery had a sticker on it that gave its capacity at 850 amp-hours. At 48 volts, that comes to 40.8 kilowatt-hours.
So, how much gasoline do you suppose it takes to match the capacity of this battery? Ten gallons? A hundred gallons? A thousand gallons? Keep in mind, like I said before, that this battery weighs about 3500 pounds, which is more than most modern cars.
It turns out that a gallon of gasoline has about 33.7 kilowatt-hours of energy that can be released by burning it. So that battery can hold the equivalent energy of about 1.2 gallons of gasoline.
The three different figures quoted above, of the alleged capacity of the Tesla S’ battery, amount to the equivalent of {53,60,85} 33.7 ÷ gives an answer of about {1.57, 1.78, 2.52} gallons of gasoline, respectively. This doesn’t, of course, take into account the tremendous advantage that electrical motors have over an internal combustion engine, but even so, at best, you can multiply those numbers by a factor of about three; and see one major reason why we are still using internal-combustion-engine-powered cars.
Another reason has to do with the rate at which batteries may be charged. I’m not going to try to recreate my math right now, but I figured out a while back that in order to charge an electrical car at a rate that is comparable to pumping gasoline into a conventional car, you’d need to be charging at a rate of a few million watts. I don’t know if it’s feasible to have usefully-placed charging stations that have access to that much electrical power, but I very much doubt if we are anywhere close to having batteries that can withstand being charged at such a rate.
Definitely do not try this at home. Taking a quick look at the circuit breakers for my apartment, it looks like they add up to 395 amps, which, at 120 volts, would be 395 120 × 47400 watts, or 47.4 kilowatts.