The Dirty Little Secret about Electric Vehicles

Electric Vehicles have gotten a lot of media attention overthe 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. Weuse things like O2 sensors and Air Fuel Ratio sensors, along with catalyticconverters, in order to reduce the impact that gasoline engines have on theenvironment. Recently, companies have been exploring ways to abandon gasolineconsumption all together and produce “zero emissions” vehicles in the form ofelectric vehicles, like the Nissan Leaf. Although people have thoughtfullyexplored 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 symbolLi on the periodic table. It does not occur freely in nature; it only appearsin compounds that are usually ionic. Lithium salts are extracted from the waterof mineral springs, brine pools, and brine deposits. The metal is then producedvia electrolysis from a mixture of fused lithium chloride and potassiumchloride.

The brine is usually pumped to large pools to let the sunevaporate the salts to a high enough concentration. Then this potent solutionis pumped onto trucks and driven to processing facilities. Currently, 61% ofthe world’s lithium production occurs in Chile. Worldwide reserves of lithiumare estimated at about 13 million tonnes. Using the battery efficiency figureof 400 g of lithium per kWh, this gives a total maximum lithium batterycapacity of 52 billion kWh which, assuming it’s used exclusively for carbatteries, is enough for 2 billion cars with the same size battery as a NissanLeaf.

Lithium brine pools

 Problem is, only 25% of the world’s lithium goes into themanufacture of batteries (and that includes batteries for laptops and cellphones).  Lithium is used for processingsilica to make glass, as a major component in high temperature grease, in airpurification systems, in nuclear weapons, and even in pharmaceutical drugs totreat bi-polar disorder. The world’s supply of lithium would be exhaustedrelatively quickly if we tried to run most of the world’s vehicles onlithium-ion batteries.

In response to this claim, many bring up the fact thatLithium batteries can be recycled, and thus diminishing the problem ofdepleting this rare metal. The problem with this is that lithium is rathervolatile at room temperature, so the entire battery has to be cooled down to-345°Fbefore it can be dismantled and recycled. Cooling batteries down to suchextreme temperatures uses a tremendous amount of energy, reducing the favorableenvironmental impact lithium ion batteries are supposed to have.

In reality, with a rapidly expanding population and ballooningconsumption of energy worldwide, there is no magic solution to solve ouremissions problems and save the world. Continuing current habits of everyindividual driving and using inefficient means of transportation, along withthe host of other issues with consumer culture, leaves little doubt that ourcurrent style of living is unsustainable. Save for the unlikely invention ofcold 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 pushfor more fuel efficient vehicles. Along with the development of catalyticconverters, 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, butmore recently, fully electric vehicles have been in the spotlight as the mostgreen and efficient option available today.

 One challenge for the EPA was how to relate the fuel efficiencyof 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 poweredvehicles, so the solution has been to provide a MPGe, or miles ger gallonequivalent, rating for all electric and hybrid vehicles.

The MPGe metric was introduced in November 2010 by the EPAto label the fuel efficiency of the new Nissan Leaf and Chevrolet Volt electriccars. The ratings are based on the EPA’s formula, in which 33.7 kilowatt hoursof electricity is equivalent to one gallon of gasoline. This is based on theenergy 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 necessarycharge the battery; and the other is the transmission efficiency of that electricity from itssource into the battery. This makes the calculations much more difficult, butit is essential for getting an accurate depiction of the fuel efficiency ofelectric vehicles.

2012 Ford Focus Electric

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