Electric car glossary: jargon busting kWh and more

Toying with going electric but baffled by EV jargon such as AC, kWh and Ah? The BuyaCar electric car glossary is here to save you...

James Wilson
Jul 21, 2021

Understanding electric car terminology is more difficult than it needs to be, because the language isn’t car specific. Terms such as horsepower (hp) and mpg are associated with petrol and diesel engines, but electric car terms such as amps, watts and volts have been used to describe everything from TVs and electric heaters to washing machines for years.

But these are all now words that can be used in conjunction with the workings of an electric car. The trouble is, anyone without the extensive knowledge of an electrician may struggle to understand what it all means. A brief look at an electric car's spec sheet might at first glance seem like a random selection of upper and lower case letters, but these letters tell an important story about the performance of the car.

If you were falling into a panic just thinking about all this electric car lingo, you can relax now, because we have laid out all the electric car jargon you're likely to come across below, explaining what it means and how it can help you decide if an electric car is good or bad. You'll go from a total novice to a Tesla Technician in just a few minutes. Slight exaggeration perhaps.

Electric car: background information

When talking about electronics for cars, the three most basic elements are voltage, current and power. In fact, these three form the foundations of much of the jargon we've busted below. To save this article from turning into an A Level physics class, consider that electricity is merely charge flowing through a wire – we can save how this actually happens for the engineers making batteries.

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 which 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

Topping up car batteries is a hot topic in the electric car world and when it comes to charging, kilowatts are very important. Written in shorthand they are shown as kW. As talked about 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.

For those wondering why people aren’t installing chargers rated at very high amounts of kW so charging is super fast, there are a few issues with high output charging. For one, an electric car’s internal circuits might not be able to handle this – 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 is the kind of electricity UK households are powered with.

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 a charging point dubbed as an AC unit.

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

Battery packs are commonly provided with a kWh figure which indicates its total energy capacity. 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 are also common when talking about electric cars, which is the amount of energy a one-watt appliance uses in an hour. Why are kWh and Wh used? They are a useful standard measurement for energy consumption, that’s why.

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

Just like petrol and diesel cars, electric cars have performance figures too. 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. What is potentially confusing is that power for petrol and diesel cars can also be quoted in kW. The reason being 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 are optimistic due to being conducted under artificial conditions rather than being on everyday roads. 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.

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 and that is all we mere mortals need to know. Anything more technical is overkill, especially as motors should be one of the most reliable, longest-living parts on an electric car.


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