Electric car glossary: jargon busting kWh and more

Are you confused by EV terms such as AC, kWh and Ah? Fear not, as the Buyacar team is here to explain everything you need to know…

James Wilson
Jan 5, 2022

To many of us, getting to grips with the unusual language of car-related terms is like trying to learn a new language. With electric cars rising in popularity, terms such as amps, watts and volts are now being used to describe cars and it can be confusing to understand what they mean. While you may recognise some of these electric car-related terms from A level science or household gadgets and appliances, it can be difficult to understand how they are relevant in the world of electric cars. It is important to understand these abbreviations and terms however, as they tell us very important facts about the performance of electric cars and how capable they are of different tasks.

While electric car lingo may be confusing, we have you covered, as we have laid out all the electric car jargon you're likely to come across below. In this guide, we will explain every term you need to know before buying an electric car. You may not be a qualified Tesla technician after reading this guide, but you will be able to understand all of the electric car jargon that they use!

Electric car: background information

When talking about electronics for cars, the three most basic elements are voltage, current and power. These three form the foundations of much of the jargon we've busted below. All of the scientific information involved in electric cars can get a bit confusing, but you only need to remember a few basic concepts to understand how electric cars work. We can leave all the complicated stuff for the engineers making the electric cars.

How fast electricity (or charge) moves through a wire is called current. Meanwhile, how much energy a circuit has to push current through it is called voltage. It is the relationship between the two of these that defines electrical power, which is roughly current multiplied by voltage. A key thing to note here is that having lots of power can come from having a high voltage or a high current or a high level of both.

For those who don’t know, the units (what something is measured in, e.g. litres or miles) of voltage are volts (V), while current is measured in amps (A) (or amperes) and finally, power in watts (W).

In an effort to bolster your pub quiz knowledge, each unit is named after a famous scientist. They are Alessandro Volta, André-Marie Ampère, and James Watt – no points for guessing which scientist got which unit…

Electric car: charging

In the world of electric cars, topping up the battery is one of the key talking points. The most common metric used when discussing the charging of electric cars is kilowatts. Written in shorthand they are shown as kW. As we mentioned just above, watts are a measurement of power, which is related to voltage and current. So it makes sense that the higher the kW output of a charge point, the more charge you will be putting back into your battery over a set time.

Our dedicated charge point article covers all the ins and outs of the different charge points available.

In an ideal world, every electric car charger would have a high energy output for super-fast charging. However, there are some issues with these high-power chargers which limit them from being used at every charging opportunity. First, an electric car’s internal circuits might not be able to handle the high output – meaning they would break if plugged into too high a wattage. Also, depending on the chemicals inside the battery pack, they may not respond well to rapid charging, especially if done over and over again.

Next in our charging jargon section is alternating current power supplies – affectionately shortened to AC power supplies. AC means that the direction in which electricity is flowing along a wire keeps switching backwards and forwards. This type of electricity is commonly found in households across the UK.

Alongside AC there are direct current or DC power supplies that only lets electricity flow in one direction. All electric batteries require DC electricity to charge. Thanks either to the electronics in your car or the charging point, AC supplied by the UK’s grid is converted to DC for batteries to use.

Most electric cars' onboard charging equipment isn’t rated to convert large quantities of AC to DC for charging their batteries. As a result, this limits charging speeds when using an AC charging point.

Rapid chargers such as those found at many service stations have the electrical gubbins inside them to convert big AC supplies into big DC supplies, enabling faster charging. It is for this reason DC charging appears to be quicker than AC.

In reality, all charging is DC and it is a car’s ability to convert an AC supply into DC that is the limiting factor in the speed of charging, rather than whether it is hooked up to an AC or DC supply.

We've also covered the finer details of the different electric car charging cables for you as well.

Electric car: batteries

Electric car batteries are often measured in kWh. The ‘k’ stands for kilo, as in '1,000 of' - just like kilogram means 1,000 grams. ‘W’ stands for watts as described above and ‘h’ stands for hour.

All in, kWh means kilowatt-hour. A kWh is the amount of energy a 1,000-watt appliance uses in an hour. Wh is also frequently mentioned when talking about electric cars, which is the amount of energy a one-watt appliance uses in an hour. Both kWh and Wh are commonly used as they are a useful standard measurement for energy consumption.

To give an example, let’s say the battery pack is rated at 10kWh. If we had a 5kW motor powering the wheels, we would be able to drive for two hours (i.e 10 divided by 5).

Likewise, if we had our 5kW electric motor plus a 3kW sound system and a 2kW climate control system running, we would only be able to drive for one hour (10 divided by 5 + 3 + 2).

Similar to kWh, we have Ah – known more formally as ampere-hours or amp-hours. Amp-hour figures tell you how much current a battery can supply for a given period of time. For example, a battery pack rated at 2Ah over a period of one hour will be able to supply 2 amps' worth of electricity for one hour.

It is important to note here that the time frame is very important as it can have huge implications on the performance of an electric car. What this means is, saying a battery has a capacity of 10Ah is useless unless you know for how long a time period this applies.

Can it do it for two, three, four, or even 20 hours? Who knows, but the longer a battery can sustain the required current, the longer it will be able to power motors and other electronics.

Electric car: performance

We often judge electric cars by their performance figures in a similar way we do with petrol and diesel cars. While the majority are the same as traditionally powered vehicles – think 0-62mph times, braking distances, etc – there are a handful of important differences.

For starters, there is power output, which for electric cars is often quoted in kW or kilowatts unlike the horsepower/hp we are accustomed to. What is potentially confusing is that power for petrol and diesel cars can also be quoted in kW. The reason is electricity isn’t the only way of getting a power output – after all, many mechanical items (such as an engine) burn fuel to release energy instead of using big batteries.

Another important thing to understand is range, quoted as either being from the WLTP or NEDC test. Both collections of letters signify a European testing procedure for assessing (among other things) an electric car’s economy and range.

The takeaway bit of information here is that WLTP figures are much more accurate for real-world range when compared to those sourced from the NEDC test. However, both tests are conducted under artificial conditions rather than everyday driving on real-world roads, so neither will be a perfect representation of the performance you can expect from an electric car. You can find out more about the latest testing procedures in our dedicated article here.

Finishing off the performance section is electric car economy, which is also referred to as efficiency or consumption. Electric car economy is typically given in some combination of set distance per Wh consumed or vice versa. For example, the 2019 Nissan Leaf is quoted with an economy figure of 4.2 miles per kWh. This could easily be written as Wh per mile, Wh per kilometre or kilometres per kWh, it really depends on the car manufacturer which can make comparing electric cars quite complicated. Not to worry, though, because we've rounded up a list of the most economical electric cars.

Electric car: electric motors

Electric motors are something of a minefield, as things get complicated quickly. With that in mind, the most common type you will see in electric cars is a permanent magnet synchronous motor.

All electric motors use a combination of magnetic fields and flowing current to drive a car down the road - the majority of us don’t need to know much more than that. Thankfully electric motors are notoriously reliable and long-lasting, so understanding anything more technical is unnecessary.

 

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