How Electric Cars Work
The three fundamental components of an electric car are the batteries, electric motor, and the electronics controller.
Fully electric cars use a high capacity battery of some variety in order to power its systems. Batteries work by storing electricity as chemical energy. They do this with three components. These are a cathode, anode, and an electrolyte. You can think of the cathode as the positive end of the battery and the anode as the negative end of the battery with the electrolyte placed between them. Reactions in the battery cause the electrons or electricity to concentrate within the anode. The electrons have a tendency to repel each other and would go to the cathode if possible however they can not pass the electrolyte. The concentration of electrons is what causes them to move because they would prefer to go to an area with fewer electrons. So the electrolyte acts as a barrier to prevent the battery from immediately losing its charge. When something such as a wire connects the cathode and anode, or positive and negative sides, electricity can flow from the negative side to the positive side and will power anything in between the two sides. When a battery that can be recharged is recharged the reactions that originally occurred in the battery are reversed which allows the process to happen again. The car uses two batteries, an auxiliary battery and a larger battery pack. The auxiliary battery is used to initially start the vehicle and is used to power smaller systems such as onboard computers. The larger battery pack is used to power the cars battery throughout its trip. The batteries are similar to a gasoline powered vehicles battery except for the fact that the electric car has more of them. They are stored under the car or in the trunk depending on the vehicle. The three common types of batteries used in electric cars are lithium-ion batteries, lead-acid batteries, and nickel-metal hydride batteries. Lithium-ion batteries are batteries that are commonly used small devices such as phones, they generally give the best performance for range and are lighter than the other types of batteries but are also the most expensive of the three types. Lead-acid batteries are the most common batteries and the cheapest and are still used in gasoline powered cars to start the engine and power auxiliary systems. Nickel-metal hydride batteries are more expensive than lead-acid batteries but also have better performance. Some electric cars also have a feature known as regenerative braking which uses a the motor to charge the batteries as the vehicle brakes in order to regain some of the energy used to accelerate. The batteries are charged at designated charging stations or a home charging station which supply the vehicle with electricity that passes to a charger inside the car that converts the electricity to a form that the batteries can store and later use. Fully charging these batteries can take several hours depending on the capacity.
Electric cars use power from the battery to power an electric motor which propels the vehicle. There are two types of electric motors that are commonly used in electric cars. These types are direct current (DC) motors and alternating current (AC) motors. DC motors use permanent magnets positioned around an electromagnet which turns on and flips polarity when supplied with electricity. The electromagnet can rotate and is pushed by the two magnets around it. Essentially the motor creates a temporary magnet and rotates it by pushing it with opposite magnetic attractions with the same principle as two magnets repelling each other if they have the same polarity. These are generally simpler and cheaper than AC motors with the advantage of quick bursts of rapid acceleration but doing this too much can result in heat buildup in the engine. AC motors work by having two pairs of coils of wire around a rotor. Electric current is supplied to the coils in a sine wave which means that when one coil is completely powered, the other one has no power. This creates a magnetic field inside of the coils and creates electricity in the rotor. The rotor’s new electric field generates a magnetic field which attempts to go against what caused it. The interaction between the rotors magnetic field and the field produced from the two coils of wire is what causes it to spin. These motors are readily available which allows cars to have various shapes, sizes, and energy consumption to match the car. The AC motors also feature the aforementioned regenerative braking. The car’s motor powers the cars motors to propel it forward. The electronics controller is the final fundamental component of an electric car. The controller takes power from the batteries and supplies it to the motors. It uses a potentiometer which is connected to the accelerator to decide how much to accelerate the vehicle. A potentiometer is a device which provides different levels of electrical resistance based on how far down the pedal is pushed. The controller then takes this electrical resistance and interprets it to determine how much to accelerate. After the controller determines how much to accelerate, it turns the the motor on and off in a ratio similar to the percentage of how far down the pedal is pushed. The motors are pulsed on and off to match the accelerator pedal in the car so that if the pedal is halfway down, the motors are half on and half off during the time it is pressed down. So in a similar way if the pedal is pushed down 25% of the way, the controller will have the motor on a quarter of the time and have the motor off three quarters of the time and at a stop the car can engine doesn’t have to run which helps efficiency. The controller also provides power to other electrical components from the batteries.
This demonstrates how the battery, motor, and electronic controller work in a fully electric car. Electric cars are becoming increasingly important as we push away from fossil fuels into cleaner electricity.
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