Today’s cars are extremely complex assemblies of all kinds of mechatronic systems. Toyota says their average car contains about 30,000 parts if you include all the screws and fasteners. That’s a lot of complexity to manage on top of the ever increasing electronics content of newer vehicles.
The basic idea of the car is essentially to power wheels for motion. Looked at as a mechatronic problem, the simple answer is to use a belt and pulleys. The mechanical advantage of this approach makes the torque requirement much lower and avoids the huge stresses of turning an extremely large load from a shaft. Why the car guys don’t get this is beyond me. But we have a long standing tradition of doing things the hard way, so I won’t interfere. For the moment.
Then there is the very simple F=ma. The bigger the “m”, vehicle weight, the more “F” you need. IF you want to push a 5800 pound car, you’re going to need a lot of horsepower. If you want to push the 5800 pound car to 60 miles an hour in less than 4 seconds your going to need a Corvette with 500 horsepower. All it takes is a little extra cash.
Then come all the complex subsystems. Engine horsepower is consumed by parasitic loads like air conditioning, alternator charging of the electrical system, hydraulic pumps to boost brake fluid pressure, etc. Numerous electrical features like the new generation of power steering assist, powered windows and windshield wipers are all examples of simple electromechanical actuators with power electronics and intelligent controls. At a certain level, it’s amazing that all this stuff works as well as it does.
When Consumer Reports does a survey of customer satisfaction about cars reliability, they get some interesting results. Among which, notably, is the Nissan Leaf. As one of a very few pure electric production cars, the Leaf gets about 3 miles per kilowatt hour If you are in a low cost of electricity market, at 12 cents/kWhr then your cost of energy per transportation mile is about 4 cents. Which compares favorably with nearly 20 cents per mile for gasoline powered cars.
What really makes it interesting is that the pure electric has nothing to maintain except the batteries. No trips to the shop for oil changes and filters, no regular maintenance to speak of. Which means incredible reliability and low cost of operation.
Getting back to the F=ma question, at a vehicle curb weight of 3500 pounds, we need a dozen car companies producing lighweight versions of the car at 1750 pounds to really make this work. A lower vehicle weight could translate to double the driving range or half the battery pack. Given that a lithium battery pack is the most expensive part of the car, I’ll take the smaller battery pack.