The competition to bring a mass produced electric car to the market is really heating up. There is an underlying assumption that, like flat screen TVs, this thing is going to happen. Like seeing flat screens in science fiction movies, electric cars have been part of the cultural consciousness for more than 35 years, since GM’s EV-1.
Ironically, it’s more like history repeating itself. Before Ford and Rockefeller partnered to make gasoline power the cheapest form of automotive transportation, the US fleet of cars was equally divided between steam, electric and gasoline power. Nowadays we have seen technology demonstrations for hydraulic and pneumatic powered vehicles for delivery companies like UPS and Fedex.
Why is it that technology choices are so limited in the auto industry?
In the case of the electric car, the issue is battery technology. Lithium battery technology has made extremely important strides that were a prerequisite to a pure electric vehicle becoming practical. Lead acid batteries won’t do it. It’s called the “battery mass fraction”. How much battery is required to provide a certain range of driving? That number does not vary much, but it is an interesting parameter to consider.
Roughly 25% of the curb weight of the vehicle must be battery in order for the vehicle to have any reasonable range. The Tesla Model S has a curb weight of 4600 pounds and a battery weight of 1200 pounds. Check.
The rule holds at any weight of vehicle. The curb weight of the New Chevy Bolt is 3580 pounds and the new battery pack is 960 pounds. Notice a theme here?
Carrying this logic further, the cost of the battery, being the biggest expense in the electric car, is predicted by its weight. The total price of the car actually declines faster as the weight falls. A smart car at $1800 pounds costs about $18,000.
This makes a case for designing a next generation electric car based on today’s technology very simple. We should be targeting a car with 2200 pound curb weight and a battery pack of 550 pounds. This brings the cost burden of the battery down to a level that insures a product that many people can afford. Without the Federal Government’s $7500 incentive discount. Which you paid for out of the Federal taxes you paid.
Next week some comments on the barriers to market entry and government’s role in all this.
Filed Under: Mechatronic Tips