The Dirty Little Secret about Electric Vehicles

Electric Vehicles have gotten a lot of media attention over the last few years. The United States, with the rest of the developed world, have made a push to reduce emissions and improve air quality in our cities. We use things like O2 sensors and Air Fuel Ratio sensors, along with catalytic converters, in order to reduce the impact that gasoline engines have on the environment. Recently, companies have been exploring ways to abandon gasoline consumption all together and produce “zero emissions” vehicles in the form of electric vehicles, like the Nissan Leaf. Although people have thoughtfully explored the impact of producing the electricity needed to charge the battery, all of the green-enthusiasts are conveniently looking away from the real issue: the lithium ion battery itself.

Nissan Leaf

 Lithium is a soft, silver-white alkali metal with the symbol Li on the periodic table. It does not occur freely in nature; it only appears in compounds that are usually ionic. Lithium salts are extracted from the water of mineral springs, brine pools, and brine deposits. The metal is then produced via electrolysis from a mixture of fused lithium chloride and potassium chloride.

The brine is usually pumped to large pools to let the sun evaporate the salts to a high enough concentration. Then this potent solution is pumped onto trucks and driven to processing facilities. Currently, 61% of the world’s lithium production occurs in Chile. Worldwide reserves of lithium are estimated at about 13 million tonnes. Using the battery efficiency figure of 400 g of lithium per kWh, this gives a total maximum lithium battery capacity of 52 billion kWh which, assuming it’s used exclusively for car batteries, is enough for 2 billion cars with the same size battery as a Nissan Leaf.

Lithium brine pools

 Problem is, only 25% of the world’s lithium goes into the manufacture of batteries (and that includes batteries for laptops and cell phones).  Lithium is used for processing silica to make glass, as a major component in high temperature grease, in air purification systems, in nuclear weapons, and even in pharmaceutical drugs to treat bi-polar disorder. The world’s supply of lithium would be exhausted relatively quickly if we tried to run most of the world’s vehicles on lithium-ion batteries.

In response to this claim, many bring up the fact that Lithium batteries can be recycled, and thus diminishing the problem of depleting this rare metal. The problem with this is that lithium is rather volatile at room temperature, so the entire battery has to be cooled down to -345°F before it can be dismantled and recycled. Cooling batteries down to such extreme temperatures uses a tremendous amount of energy, reducing the favorable environmental impact lithium ion batteries are supposed to have.

In reality, with a rapidly expanding population and ballooning consumption of energy worldwide, there is no magic solution to solve our emissions problems and save the world. Continuing current habits of every individual driving and using inefficient means of transportation, along with the host of other issues with consumer culture, leaves little doubt that our current style of living is unsustainable. Save for the unlikely invention of cold fusion, we are going to have to re-evaluate the way in which we travel.

What is MPGe?

Greater environmental protection measures have led to a push for more fuel efficient vehicles. Along with the development of catalytic converters, air fuel ratio sensors, and O2 sensorsfor standard gasoline engines, automakers have looked for alternative ways to fuel our transportation needs. Most popular today are gasoline-electric hybrids, but more recently, fully electric vehicles have been in the spotlight as the most green and efficient option available today.

 One challenge for the EPA was how to relate the fuel efficiency of fully electric vehicles to consumers. We are all used to the standard MPG – or miles per gallon – rating to compare the fuel efficiency of gasoline powered vehicles, so the solution has been to provide a MPGe, or miles ger gallon equivalent, rating for all electric and hybrid vehicles.

The MPGe metric was introduced in November 2010 by the EPA to label the fuel efficiency of the new Nissan Leaf and Chevrolet Volt electric cars. The ratings are based on the EPA’s formula, in which 33.7 kilowatt hours of electricity is equivalent to one gallon of gasoline. This is based on the energy content of gasoline: burning one US gallon of gasoline is 115,000 BTU. The formula for calculating MPGe is shown below.

Two things must be taken into consideration for MPGe of electric vehicles: one  is the energy consumed to generate the electricity necessary charge the battery; and the other is the transmission efficiency of that electricity from its source into the battery. This makes the calculations much more difficult, but it is essential for getting an accurate depiction of the fuel efficiency of electric vehicles.

2012 Ford Focus Electric

 Even with all those factors taken into consideration, new all electric vehicles have impressive fuel efficiency. The 2012 Ford Focus Electric gets 105 MPGe and has a range of 76 miles. Certainly not capable of road trips, but it will get most people to work and back, and perhaps a trip to the grocery store, with some charge to spare. This satisfies what most people do with their cars on a daily basis, and can save a good amount of money in the long run on gas.

Does MPGe make sense to you?

What is a Knock Sensor

The knock sensor is the unit in the car that protects against incorrect timing issues. It allows the engine to run with the timing advanced as far as possible without damaging the motor or loss of power. Unlike oxygen sensors or the air fuel ratio sensor the knock sensor will not allow the car to run incorrectly. A knock sensor feed info to the ECU and if the car is knocking too much to be adjusted by timing to will send the ECU into a safe mode which will stop the engine all together.

The knock sensor works by responding the knock caused by pre-detonation of the air/fuel mixture. When the fuel mixture in a cylinder is ignited there is a flame front that moves out from the source of the spark. When this pressure wave hits the cylinder walls it makes a noise and this is detected by the Piezoelectric element in the sensor and communicated to the ECU.

When the ECU detects these that are not at the correct time it triggers an adjustment in the motors timing. If the knock sensor fails it can cause the vehicle to run very rough or not start at all. When failure occurs a trouble code is triggered which may show as the sensor or as something else in the motor. A huge factor to remember with ECU codes is that they only show the source of the code, not the issue. In other words the code may be caused by a loose wire but it says knock sensor, it is important to remember this when diagnosing an issue. 

What Does a Knock Sensor Do?

Knock sensors are the units in vehicles that monitor the pinging in the motor and help control the timing of the engine. The computer uses the input from the knock sensor along with the O2 sensors and air fuel ratio sensor to adjust the timing and fuel mixture in the pistons.

The engine in a modern vehicle has to be kept in perfect timing to ensure the top of efficiency and performance. This is done by toeing the line between running perfect and detonation. The perfect ignition of the air / fuel mixture happens at the exact moment that the piston is about to reach the top of its stroke. The timing is set this way to ensure the pressure has time to begin pushing the piston back down. When the spark plug is fired with the incorrect ignition timing or fuel mixture the pressure waves move out from the flame wall faster than the explosion itself. When this happens they impact the side wall at the incorrect time and a sound wave is created and detected. The element in the knock sensor is designed to detect this sound and alert the computer to adjust the timing.

All sensors in a vehicle are extremely important and are generally overlooked on basic maintenance. During automotive check ups it is important to remember to check the smaller parts such as sensors and filters to ensure protection from future issues.