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 marked 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:

  1. 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 direct petroleum consumption (However, petroleum is consumed to prospect for, mine, process and transport the fuels necessary to run electrical power plants, predominantly coal in the US.)

    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 mass of the battery, since every extra kg 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 “mass compounding” that drives up the vehicle mass much more than just the added battery weight to achieve greater range between battery-charging.

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 AIV Mercury Sable with an ultra-light aluminum body to minimize total vehicle weight and maximize range.

1913 Edison Electric

GM’s EV1

Tesla Roadster

Nissan Leaf

Mitsubishi i-MiEV

Ford Focus BEV

Ford Focus BEV

The BEV weight vs. range lines are concave upward; this non-linearity is due to “mass compounding”: Adding extra batteries to increase the range of a BEV requires slightly heavier support structure, slightly heavier suspension systems to provide a smooth ride, and slightly heavier brakes to safely stop the heavier BEV.  But these weight increases reduce the fuel economy of the BEV which in turn require still more batteries to achieve the desired range in a nonlinear feedback mechanism. The FCEV line also increases slightly with increased range since more hydrogen is required for longer range (and is also slightly concave upward due to mass compounding). The hydrogen weight is negligible, but the hydrogen tanks are slightly heavier to carry more hydrogen.

The three curved BEV lines clearly show the progression of improved battery performance from lead acid (Pb-A) to nickel-metal-hydride (NiMH) used on the original Prius HEVs and advanced Li-ion batteries that meet the long-term USABC commercialization goals. A line is also shown for the current Nissan Leaf with a range between 83 miles (EPA measurement) and 100 miles (Nissan claim) with the current Leaf battery that has a specific energy of 80 Watt-hours/kg [Vs. 150 Wh/kg for the advanced Li-ion battery pack used in this model.]

(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.

     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 most early hybrid electric vehicles store much more energy per unit mass. 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.  Most battery experts expect Li-ion batteries 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.

T3 Motion 3-wheel BEV

T3 Motion 3-wheel BEV

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. These calculations also assume that these vehicles are designed according to modern automotive standard designs that follow the average component weights in the mass compounding equations that are used in average late model 5-passenger vehicles. Note that hobbyists could build a BEV with longer ranges than shown here by cutting corners on the weights of auxiliary vehicle components such as body structure, brakes, suspension systems, etc.

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