Glossary

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Term

Meaning

AC

"Alternating Current" - an electric current that reverses direction at regular intervals. Electric car motors are either AC or DC (see below), with most of the new breed being of AC type.

Amp

A unit of electric current.

Battery

An electricity storage medium that feeds electric current to the motor. Older EVs used lead acid or NiMH batteries, but modern electric car batteries are of lithium ion construction (see below).

BHP

"Brake Horsepower" – the actual power output of an engine or motor before any natural losses in power through components such as a gearbox and other ancilliaries.

Charging

’Refilling’ an electric car's battery with electricity. The time a battery takes to charge depends on the size of the battery in kWh and the amount of electric current being supplied. Electric cars can take different levels of charge, meaning they can be fast or rapid charged.

Charging Point

A location where electric vehicles can plugged in and charged. These can be at home, at work or in publicly accessible locations.

DC

"Direct Current" - an electric current of constant direction. Electric car motors are either DC or AC, with DC motors generally being less expensive to buy and simpler to use on an electric car.

EV

"Electric Vehicle" - any vehicle that uses electric motors, either in full or in part, as propulsion. This includes pure electrics, hybrids, plug-in hybrids, extended range electric vehicles and hydrogen fuel cell vehicles.

E-REV

"Extended Range Electric Vehicle" - a vehicle that uses an electric motor for propulsion but also has an internal combustion engine onboard to provide power for a generator, which maintains a minimum charge level on the battery – as long as petrol in the tank is topped up, an E-REV has unlimited range. E-REVs can be plugged in and charged up, allowing an electric range of around 40 miles before the ICE fires up. Unlike a PHEV, E-REVs don't use the petrol/diesel engine to directly power the wheels.

Fast Charge

Charging at a higher current than a domestic supply (about 7kW as opposed to 3kW). This will fully charge an average electric car in three to four hours. Rapid charging is quicker still (see below).

HCU

"Home Charging Unit" - a dedicated charging point for use at home. These incorporate a number of safety features to prevent fires or short circuits and often employ intelligent features such as timers and fast charging. HCU's aren't absolutely necessary but we recommend them for peace of mind.

HP

"Horsepower" - a unit that is used to measure the power of engines and motors. One unit of horsepower is equal to the power needed to lift 550 pounds one foot in one second.

Hybrid

A car that integrates a small battery and an electric motor to enhance the efficiency of the engine. The battery’s charge is maintained by the ICE engine - it cannot be charged by plugging into an electrical supply. Hybrids can offer greater fuel economy than a traditional ICE but can only travel very short distances on electric power only.

ICE

"Internal Combustion Engine" - an engine powered through the burning of fossil fuels. The term 'ICE' is often used as shorthand for any vehicle powered by an internal combustion engine, whether petrol or diesel or any other flammable medium.

kWh

"Kilowatt-hour" - a unit of energy equivalent to the energy transferred or expended in one hour by one kilowatt of power. Electric car battery size is measured in kilowatt-hours, so think of it as the electric car's equivalent of litres of fuel in a petrol tank.

Incentives

Many governments offer incentives to encourage buyers to choose an electric car. Grants towards the purchase price exist in many countries, for example the UK's Plug-in car grant, which offers 25% off a new electric car’s list price up to £5,000. Other incentives for EVs can include free parking, zero road tax, low company car tax and exemption from city emissions and congestion charges.

Lead Acid Battery

A type of battery used in less modern electric cars. The energy density is much lower than that of lithium Ion batteries, which is the current standard. That means less power output and the need for more frequent charging. Lead acid batteries also have a shorter service life. They are, however, a lot cheaper than lithium ion batteries.

Lithium Ion Battery

These are the current standard in electric vehicle batteries, offering good energy density, power and fast charging ability. The life of a lithium Ion battery is estimated to be the same as the life of the car (eight to ten years). Of course 'end of life' here does not mean the cars or batteries won't work - after 10 years a lithium ion battery is expected to be at 80% efficiency, so they will still be usable - replacement will be a choice, not a requirement. Should you wish to replace your car's battery, it's possible they will still be in demand as storage devices for renewable energy in industry. They are expensive at the moment, but prices will reduce over time as more EVs hit the road.

NiMH Battery

"Nickel-Metal Hydride" - a type of battery used in some older electric vehicles, offering better energy density than lead acid but less than lithium ion.

PHEV

"Plug-in Hybrid Electric Vehicle" - a type of car that is configured like a regular hybrid, but with a bigger lithium ion battery pack that can be charged up by plugging in to a regular electricity supply. Pure electric driving is increased over a standard hybrid (12.5 miles on the first example to market, the Toyota Prius Plug-in) before the ICE fires up to help power the wheels. PHEVs, as they are known, offer the chance to make short journeys on cheap, zero tailpipe emission electricity but also enable long journeys.

Plugged-in Places

A UK government scheme that provides funding for specific regions to kick-start the use of electric vehicles locally and test charging infrastructure. Different 'PIP's are trialling different technology, with the results helping to inform national EV infrastructure decision-making.

Pure Electric

A vehicle powered solely by electric motors using power provided by on-board batteries. The batteries are charged using electricity from the national grid.

Photovoltaic Cells (PV)

Used on solar panels to convert radiation from the sun into electricity. Solar panels are becoming much more commonplace and can be installed at home to help charge electric cars, allowing true zero-emission motoring and a large cost saving over time. Even in the UK, users report it is possible to completely charge electric cars using solar power only. Feed-in Tariffs may also allow unused electricity to be supplied to the national grid, meaning you could earn money from installing a solar panel.

Quadricycle

A four-wheeled vehicle with low power and of the same class as a moped or scooter. Electric quadricycles do not have the performance of the latest breed of electric cars and as they are not subject to the same stringent crash testing, safety is a concern. The Reva G-Wiz is an example of an electric quadricyle.

Rapid Charge

Rapid charging occurs only at dedicated locations and employs a 20-50kW current, allowing an 80% charge of a typical electric car in around 20-30 minutes. Some rapid chargers can top up the remaining 20% at a reduced rate in order to preserve the life of the battery. Regular rapid charging is not good for the long-term life of the battery, but does offer the chance to top up on the occasional longer journey.

Range

The distance you can travel on pure electric power before the battery requires a recharge.

Range Anxiety

A term used to describe the fear of running out of battery while driving a pure electric car. Real-world accounts suggest range anxiety isn’t as common as thought, and trials show that anxiety recedes over time as drivers become more comfortable with their cars’ actual range capability.

Regenerative Braking

An energy recovery system used in most electric vehicles that can help charge the battery while the car is slowing down. Typically the electric motor acts as the generator, so power can flow both ways between it and the battery. 'Regen' helps extend the range, while the process also help slow the vehicle in a similar way to engine braking in an ICE powered car.

RPM

"Revolutions Per Minute" - the number of times the shaft of an electric motor turns through 360 degrees in one minute.

Three-phase electric power

In an AC motor in an electric vehicle, three-phase current is used instead of single phase, as it generates a rotating magnetic field from zero RPM and is typically 150% more efficient in the same power range. In other words, high torque at zero revs is made possible by a three-phase system on an AC motor.

Torque

The twisting force that causes rotation. In the case of cars, torque rules and is the major factor in a car’s accelerative ability – with generous torque, the car’s throttle response is much sharper. Petrol and diesel engines deliver torque over a curve as RPM increases, meaning they have peak power at a given RPM. Electric motors, on the other hand, deliver maximum torque from zero revs, meaning acceleration from standstill can be phenomenal.

V2G

"Vehicle-to-Grid" - transferring electrical current from the battery of an electric car back into the National Grid while plugged in to the mains. V2G could help balance the grid in periods of high demand, alleviating the risk of power cuts.

W2W

"Well-to-Wheel" - measuring the CO2 emissions of a car, taking into account the production of the fuel or electricity. This is a fair analysis of the impact on the environment of electric vehicles, as they have zero emissions at point of use but clearly have an environmental impact earlier in the chain. However, for a fair comparison with an ICE vehicle, W2W must also be calculated in the drilling of the oil, refining and transportation, not just the tailpipe emissions. Taking this into account, an average electric vehicle will produce 80g/km of CO2 compared with 147-161g/km for an ICE (source: SMMT).