Battery Electric Vehicles

EV battery history. Battery-powered electric vehicles predate the internal combustion engine. In 1899 and 1900 more electric vehicles were sold in the US than gasoline and steam cars combined. Initially these electric vehicles were used primarily in the city, as roads were often nonexistent in rural areas. Range was adequate for city driving, often exceeding the range of steam engines between stops for water. Electricity was scarce outside of cities, with both AC and DC and different voltages offered, making long distance travel with electrics nearly impossible.

Once roads became more passable, gasoline became available, and Henry Ford began cranking out his Model T’s, battery EV sales dropped after reaching a peak in 1912.

What a difference a century has made! GM’s modern 2-passenger EV1 marks a dramatic evolution since the original battery cars, with 80 miles range between battery charges and a smooth, aerodynamic body. Regrettably for those who were fortunate to lease these beauties (at heavily subsidized prices), GM decided that they were too expensive to maintain with only a limited market and they therefore canceled the program, recalling and crushing the EV1s and the hearts of those who loved them.

The advantages of a battery electric vehicle include:

Zero tailpipe emissions

No volatile organic compounds (VOCs)
No carbon monoxide (CO)
No nitrogen oxides (NOx)
No tailpipe particulate matter (PM)
No carcinogenic compounds
No sulfur oxides (SOx)

Zero petroleum consumption
The potential for zero or near-zero greenhouse gas emissions in the long run(depending on the source of electricity, which is predominately coal-based in the US today.)

New battery technologies. Batteries have improved dramatically over the last few decades, driven primarily by the need for long-life portable electronic equipment such as cell phones, cameras and laptops. For an electric vehicle, the greatest challenge is to reduce the weight of the battery, since every extra pound requires a slightly heavier car frame, a slightly larger motor to accelerate the extra weight, and slightly larger brakes to stop the car....a process known as “weight compounding” that drives up the vehicle weight much more than just the added battery weight.

The lead acid (Pb-A) batteries that have been used on motor vehicles for over 100 years were adequate for running the lights, the battery and, most importantly, for running the electric starter motor. But stashing enough Pb-A batteries on a car to drive more than 50 to 80 miles is a major challenge.

BEV weight (mass). The graph below shows the mass of a 5-passenger, full-performance battery electric vehicle (BEV) as a function of the vehicle’s range between battery charging for three different battery technologies. These BEV designs are based on a special Mercury Sable with an ultra-light aluminum body to minimize total vehicle weight and maximize range.

(AIV Sable ICV = aluminum intensive vehicle; a very light weight Mercury Sable body with a conventional internal combustion engine) All range estimates are based on a 1.25X accelerated EPA combined driving cycle; that is, each velocity step in the EPA cycle is multiplied by 1.25 to more closely approximate typical American driving habits.

The horizontal line shows the curb weight (1,300 kg or 2,875 lbs) of the aluminum intensive gasoline Sable for reference. Any BEV range above 50 to 60 miles would require added weight and therefore extra stored battery energy to travel a given distance. The three curved lines clearly show the progression of improved battery performance from Pb-A to Li-ion.

Lead-Acid (Pb-A) Batteries. An EV with Pb-A batteries with the same weight as a conventional Mercury Sable (1,650 kg or 3,640 lbs without the aluminum body and frame) would be limited to 40 miles range; if the car could accept the weight and reduced fuel economy due to 50% increased weight, it might achieve 60 miles range.
Nickel metal hydride (NiMH) Batteries. NiMH batteries such as those used in the Toyota Prius hybrid electric vehicle store much more energy per unit weight. A NiMH BEV with the same weight as the conventional steel body Sable could travel 90 miles; with 50% higher weight than the AIV Sable and resulting loss of fuel economy, it might achieve 130 miles range on a single battery charge.
Lithium-Ion (Li-ion) Batteries. The new kid on the block for BEVs is the lithium ion battery. While no major auto companies are yet using Li-ion batteries in production, most experts expect them to become prevalent when safety issues are resolved to the satisfaction of corporate lawyers and costs are reduced. As shown in the figure above, an advanced Li-ion BEV could in theory achieve 170 miles range with a Sable weight limit, and possibly as much as 250 miles range if the BEV could tolerate a 50% weight increase over the AIV Sable.

Note: these range estimates are based on mid-size, 5-passenger sedans using realistic driving cycles that mimic actual US driving habits, not the anemic EPA driving cycles. Longer ranges can be achieved with smaller, more aerodynamic bodies such as the GM EV-1 or the Tesla 2-seat roadster.