Okey doke. It's a fair cop to describe the battery the way Q described it. If it was a gasoline tank, there's be a bit at the bottom you're never gonna get to, so when you're told you have an 'X' gallon gas tank, that's a start, but unless you drive to exhaustion and manage to fill up, you're never gonna know for sure. (I know for sure with my car!).

Back to the battery. Accepting the 8.8 kWH (kilowatt - hour) figure, let's talk about that. In basic terms, that means it will put out 8.8 kilowatts of power for an hour. In THEORY it means it will put out 4.4 kilowatts for TWO hours, or 17.6 kilowatts of power for a half hour. Due to the realities of chemistry, the reality is the rate of power use directly affects the capacity of the battery AND it's lifetime. The manufacturer will have standardized on the most likely power draw the battery is expected to provide. For argument's sake, and because it may even be close to reality, let's say the battery will actually put out 8.8 kWH for an hour:

8.8 kilowatts is about 11 horsepower. That may be all that is required to overcome air resistance once you are up to speed. But how do you get up to speed?

By applying more horsepower, hence more kilowatts. If you've got say a 50 kilowatt motor, you can accelerate, as you English say, jolly fast. You will also suck out electric power out of battery real fast, but this will occur over a period of seconds, hence it will not necessarily be a noticeable battery killer, (note of faith, a competent battery designer will have designed the battery to take this kind of use becaust it is absolutely part of the known requirement to drive a car).

So you get up to speed and need about 10 horspower to push the thing against friction and wind resistance. Wind resistance and the car's drag coefficient will determine the speed you can reach. Wind resistance is related to the front of a car's cross sectional area and increases as the square of the car's velocity relative to the air. (Wind resistance is also related to the overall skin area of the car, but the relationship is less critical).

How about going up and down hills? Going up a hill will increase that horsepowe draw in a predictable manner, because you are fighting gravity and that is easy to calculate. You then have to know how long the battery can supply that extra current and you'll get a good idea of how much range you've lost. Going back down a hill may or may not allow you to recover a portion of the potential energy depending on whether or not the car uses regenerative breaking. Toyota Prius is designed that way. It's hard to imagine an electrical engineer who would design (or buy) an electric car without regenerative breaking, but it makes for a more complicated design.

This explains to me why the Chevy Volt has such limited electric range (40 miles) because of its 11 horsepower for an hour availability to do work.

All of the physical constraints on moving around apply to gasoline just the same way as on electricity, but gasoline (and petrochemicals in general) is one of the best ways to store a huge amount of energy in a small amount of space. We sort of live in a fool's paradise of cheap easy abundant energy. Batteries while they CAN be very efficient are only efficient at certain rates/ temperatures/ conditions of use, and they are not able to store energy in a 'dense' way, so that 8.8 kilowatt hour of available energy comes at a high weight.

This is not at all to put down electric vehicles. I'm just attempting to summarize a 'state of the art' snapshot. I've thought of getting a Prius many times to celebrate my crid-life misis!