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Terminology Clarification of Electric Vehicles

direct current (DC)

batteries and the majority of electronic circuitry use power in this form.

Electrons move in a single direction when there is direct current. Electricity is transferred in the power grid as alternating current (AC), so whenever the battery of an EV is charged, AC must be converted, or rectified, to direct current (DC). The onboard charging module, a hidden component, allows the automobile to charge at Level 1 and Level 2 on its own. Before supplying the DC straight to the car’s battery and avoiding its onboard charging module, which is a choke point for current flow, DC fast chargers correct the AC externally utilizing large components that are frequently hidden away from the charging area.

Even while some EVs use DC drive motors, the majority have AC motors, therefore in order to accelerate, the car must convert the DC from the battery to the AC, then back again when braking with regenerative energy. Although DC-to-AC conversion, also known as rectification and inversion, results in inefficiencies, automakers that choose for AC motors consider the performance and efficiency of the vehicle as a whole rather than just one part or procedure. For what it’s worth, despite the fact that direct current dominates the car as a whole, even a traditional vehicle depends on AC through the employment of an alternator, a generator that creates alternating current.

DC fast charging

a form of public charging that, by supplying higher voltage DC directly to the battery pack, may charge compatible vehicles considerably more quickly than the quickest Level 2 AC charger. DC fast chargers are Tesla Superchargers.

As EVs are already available, DC fast charging is ideal for sporadic charging when time is limited (e.g., when taking a long trip or running low on range). Even though “rapid” is in the name, novice EV drivers won’t find DC charging to be as quick as filling a gas tank, which may extend range by hundreds of miles in a matter of minutes. The DC fast-charging claims made by automakers typically refer to 30-minute sessions, but these hardly ever constitute a full charge. Although more and more automakers offer some complimentary DC fast charging with the purchase of a new EV, practically all of them admit that regular fast charging will shorten the battery pack’s lifespan. Fast charging is more expensive than public Level 2 charging when there is a fee, which is typically enough to offset the cost savings associated with home charging for electric vehicles.

Fast chargers for DC are extremely expensive to install in homes due to their need for three-phase AC electricity. The power they offer ranges from 24 to 350 kW, however there is no assurance that the EV will charge at that pace independent of its own acceptance criterion.

drag coefficient (Cd)

a measurement of a vehicle’s resistance to the air it travels through

Modern automobiles’ more streamlined design is a result of an aerodynamics trend that was started decades ago, partly to increase fuel efficiency. Drag opposes the effort of the engine or drive motor in the same way that a stuck parking brake or any other kind of resistance would. A vehicle’s motor works harder and consumes more fuel, whether it be gasoline, diesel, or electricity, the greater the drag coefficient.

Along with size and shape, a vehicle’s underbelly surface and height above the ground also have an impact on its coefficient of drag. Because ground-hugging cars are typically more aerodynamic, newer cars with active suspensions are frequently built to automatically lower themselves at highway speeds. It is no accident that hatchbacks are more aerodynamically efficient than classic sedan or coupe shapes with trunks that abruptly drop back from the roofline. The most efficient vehicles on the market are often hybrids and electric automobiles. Future vehicle models are being reduced by hundredths of a point by designers who labor in wind tunnels. Engineers have focused on airflow around wheels, into and over engine compartments with active grille shutters, and past exterior door handles, which are increasingly retreating flush with the side of the body, after going as far as they can with overall forms. If not for federal and state requirements that specifically call for mirrors, side mirrors have long been a target and would be replaced by cameras.

EVSE

equipment for servicing electric vehicles (or supply equipment)

An electric car charger, whether it be the standard trickle charger wire or a more durable Level 2 device you might install at home or find at a public “destination” charging station, is referred to as an EVSE. The nomenclature is different since in electronics, the part that controls battery charging and, if necessary, transforms AC to DC is technically referred to as a charger. These two things are not performed by the EVSE. You can’t see it, but each car contains an inbuilt charger that performs these functions. The EVSE is basically a safety device that guards against harm to both you and your car. It only includes a ground-fault circuit interrupter, some switching, and circuitry that can signal how much power an EV can get from it.

240 volts is a lot to hold in your palm, especially if you’re outside in the weather, whether it has a J1772 or Tesla connector. Until the connector is connected to the EV, the EVSE won’t deliver high voltage to the cable. The EVSE’s pilot signal, which indicates how much power it can supply, is detectable by the automobile once it has been attached. When charging is ready to start, the EVSE flips a powerful switch known as a contactor, energizing the cable. This contactor usually makes a clicking sound. Similar to this, if you try to remove a connector from an EV, both the car and the EVSE will immediately stop charging, ensuring your safety.

inverter

a device for electronics that switches direct current to alternating current

Because the vast majority of electric motors used in both types of vehicles are AC but batteries are always DC, traction inverters—so named because their only function is to make AC to power an AC traction motor—are essential components of both electric cars and the majority of hybrids. Due to Ford’s usage of the technology in its Pro Power Onboard option, which powers 120- and 240-volt outlets in the beds of 2021 F-150 hybrids, the term “inverter” has also become widely used (and, next, F-150 Lightning EVs). The hybrid battery pack alone can power this system, albeit a low charge level will trigger the hybrid truck’s engine to start. Backup generators made by Pro Power Onboard that produce AC, correct it to DC, and then invert it back to AC are being recalled. Although it looks silly, this redundant conversion enables inverter generators to operate at varying engine speeds dependent on load, which is a more effective and quieter method while leaving the generation of AC to the electronics Conventional generators, on the other hand, are actually alternators that must run continuously (at full speed and output, essentially) in order to preserve a constant 60-hertz AC cycle.

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Electric Vehicles: Understanding the Terminology

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