Electric car batteries explained

With an electric vehicle (EV), it’s all about the battery.

The battery determines how far a car will go when fully charged, how long it takes to recharge, how long it will last and almost any other aspect of the vehicle.

As such, the battery pack is currently the most expensive component of an EV, although this is set to drop over coming years as they continue to be built in larger volumes and manufacturers can take advantage of economies of scale. Further on in the decade, we might also see new, less expensive types of battery.

Whatever its cost, the battery will remain one of the most important parts of any EV.

What is an electric car battery?

We’re not going to lie: making the most of a battery’s energy is still something of a dark art, with a load of physics and chemistry involved.

Yeah, us neither, so the good news is that a battery pack is all sealed up and only accessible to trained technicians. It should be reliable for a good few years, so we don’t have to worry too much about how it works.

That said, it’s always good to know the basics so, as the ads say, here’s the science part.

A battery pack is made up of lots of cells, which are packed together in modules. The modules are then packed together in a case, with all the electronics that enable the car to access the battery’s power. This is the battery pack.

Your EV battery is pretty much the same as the one in your smartphone or laptop. A lot bigger, obviously, but it’s a lithium-ion battery. This type of battery has the best energy density, which means there’s more available energy per cell than other types of battery.

There are currently lots of experiments with other ‘battery chemistries’, as they’re known, which means that we could see different types of batteries (iron phosphate, for example) in EVs in the coming years.

But for now, lithium-ion batteries are the only game in town.

How electric car battery energy works

The next thing to understand about batteries is their energy capacity, which is expressed in kilowatt hours (kWh) - this is a way of describing how much power (the kilowatt part) will use over a period of time (the hour bit).

Generally speaking, more kWh in a battery, the more miles you'll go on a single charge. If you have a relatively small EV with a battery over 60kWh, for example, you can expect a range of 250-300 miles. A larger, heavier car, however, might have the same size battery, but the range won’t be the same, because it has to use more energy to shift the bigger car.

It's also worth remembering that higher-performing cars that produce more power and achieve impressive 0-60 times will drain their battery faster to do so. So while a Tesla may have a range of well over 200 miles, if you're using all that performance, all the time, you won't get the maximum range. 

Battery size isn’t the only factor in how far an EV can go on a single charge – there’s all kinds of clever software that the brainiacs working for car companies (and their suppliers) are developing, which somehow manage to wring more range out of a battery – but, as with many things in life, bigger is often better.

Charging an electric car battery

Obviously, once your car’s battery is out of energy, it needs to be recharged.

You’ve probably noticed that EV manufacturers often quote the time it takes to achieve an 80% charge, not 100%. The main reason for this is that the last 20% takes longer to charge relative to the first 80%. However, if you want to look after your EV’s battery, you can extend its life by not charging it fully.

How quickly your EV charges depends on the type of charger you use, with different units having different charging speeds.

Charging from a domestic three-pin plug is the slowest way, but if you can charge overnight, that will work for most owners. Then you have 7kW and 22kW chargers, which are either home-charging wall box units or the types of public chargers you find in car parks, on the street or at leisure centres or shopping malls. You can usually get to 80% charge in three or four hours.

Next fastest are the 43kW-50kW chargers, for example. In just over half an hour, you can get an 80% charge. We call the 50kW chargers Medium Power and you'll find these at motorway services across the UK. 

The big breakthrough in recent years has been the emergence of High Power chargers. These 350kW-capable chargers, which you'll find at our Electric Forecourts® and Electric Super Hubs across the GRIDSERVE Electric Highway, can supply an 80% charge in just 10-15 minutes. 

Not all EVs charge equally fast, though. More recent models – especially at the more premium and luxury end of the scale – can take electricity onboard at the rate the ultra-rapid chargers can pump it out.

Temperature is another factor in determining charging speed. Batteries operate optimally at between 20-25°C. If the outside temperature gets too cold or too hot, the battery management system (BMS) will reduce the power input to protect the battery. This reduction means that the car takes longer to charge.

Some of the latest EVs, like the Porsche Taycan, come fitted with a system that regulate the battery’s temperature, so it’s always at the right temperature when you plug in.

How long do electric car batteries last?

We’re used to batteries in our smartphones and laptops losing charge quicker after a few years and having to plug in every night. So, perhaps rightfully, you might assume the same for batteries in the electric cars – they use the same lithium ion technology after all.

Well, fortunately, you can rest easy. Your electric car battery will not need upgrading or replacing. It’s good for many, many years and even more miles. And here’s why.

Clever engineers have developed advanced battery management systems that ensure the long-term health of your battery, such as preventing over-heating. That means, that yes, while lithium ion batteries degrade over time, the one in your car will happen extremely slowly.

Don’t just take our word for it though, look at the evidence. The Nissan LEAF launched in 2010 and over half a million have been sold. Guess how many have experienced battery failure… three. Less than 0.0006%. Fleet management companies have found that the average health of a battery after five years is still 89.9% while some companies are now offering 10-year warranties on their battery packs to give you complete peace of mind.