Not so long ago, the question was: is a diesel- or petrol-powered car right for me? Then hybrid muscled in on that equation, laggardly followed by plug-in hybrid. Then, of course, electric cars entered the fight, and the biggest question of all became whether or not an electric car was right for you, or me – a question which, more than a decade on from sales of electric models kicking off, still has no straightforward answer.
Now, though, we’re starting to drill down into the finer details of electric cars. With prices coming down and ranges going (somewhat) up, the question now is less whether an electric car is the right purchase, but which type of electric car?
Because there is more than one, and specifically more than one type of battery. For now, electric motors are pretty homogenous (at least until clever axial-flow motors, or in-wheel motors start to become commonplace), so the defining characteristic is the battery.
The vast majority of current electric vehicles use lithium-ion batteries. These batteries come in either cell, prismatic or pouch types. Cell batteries look rather disarmingly similar to domestic AA batteries, but don’t be deceived – pack enough of these together into one big battery stack and you have enough power to run a Tesla. Literally. Pouch cells look more like little tinfoil bags, while prismatic cells look broadly similar to pouch cells but are more expensive to make.
Whatever the shape, they all use the same basic chemistry, using nickel-manganese-cobalt (NMC) anode (that’s the negative terminal) and cathode (the positive) to get ions of lithium to flow through the battery. Flow in one direction charges the battery up, flow in the other direction sends an electric current out to a motor, driving the wheels.
What are the pros of a lithium-ion NMC-type battery?
Well, the chemistry is well understood (it’s the same basic stuff you’ll find in your laptop or mobile phone) and the designs have matured. Make a lithium-ion battery big enough and you can extract impressive ranges on one charge, such as the new Volkswagen ID.7 which, with its biggest 83kWh battery pack, can manage almost 700km in one go (in theory, in ideal conditions etc, etc).
The downsides, though?
Lithium-ion batteries are expensive to make (although they are getting cheaper) and use vast quantities of rare metals and minerals which have to be dug out of the ground – in itself an energy-intensive process, and one that has sounded alarm bells on such matters as human rights and child labour in the mining industry, and political issues such as China’s near-total dominance in lithium processing. Lithium-ion batteries are also heavy, leading to heavier and less efficient cars, and if damaged they can suffer ‘thermal runaway’ – a fire which is very difficult to extinguish.
Is there something better out there?
Yes, there is. Lithium-iron phosphate batteries, or LFP batteries. These are now starting to become more commonplace, and they have some significant advantages over lithium-ion packs. For a start, they’re more affordable to build, and their chemistry means that you can forgo some of the harder-to-mine rare-earth metals such as cobalt. They’re also more rugged – BYD, which has pioneered LFP batteries, integrates them into the structure of the car for improved crash protection – and less likely to suffer thermal runaway.
The downside is that they generally hold less energy for a given size, making for shorter ranges (although it’s worth pointing out that in real-world conditions, thus far, LFP batteries seem to stack up well against lithium-ion ones), and they’re less easy to recycle – a critical factor as given the paucity of lithium and other materials on the planet, when the time comes for mass-adoption of electric cars, many of the batteries are going to have to be made out of old, recycled batteries.
One major advantage of LFP batteries is that, generally, there’s no issue with constantly charging them to 100 per cent capacity, unlike lithium-ion batteries, which generally come with a health warning to charge them to 80 per cent most of the time, and only topping up to 100 per cent for occasional long journeys. However, they’re often slower to charge than the best lithium-ion batteries.
What about solid-state batteries?
These are essentially lithium-ion batteries, but instead of the centre of the battery using a liquid core through which the power flows, there’s a solid mass, usually a form of ceramic. This has, potentially, massive advantages including more reliability, less likelihood of thermal runaway and incredibly fast charging. The problem is that while solid-state batteries have all the promise in the world, no one has yet managed to get them into proper mass production, with the best estimates being that we won’t see a solid-state equipped car on sale until 2028 at the earliest.
For many of us, the critical question will be how quickly a battery can be recharged and you can get back on the road again. For this, sadly, there is no simple, straightforward answer. The very best charging systems – those deployed by Porsche, Hyundai and Kia – run on 800-volt energy, and can swallow more than 300kW of direct current (DC) rapid charging, potentially allowing fast charges of less than 20 minutes to get to 80 per cent power. This makes life much easier if you’re a long-haul driver, but it involves finding and being able to use an ultra-high-powered charger, of which there are not many.
Most other cars run on 400-volt power, which generally allows for charging at up to 200kW of DC power, which usually means 80 per cent recharge times of about 30 minutes, but again that’s (a) assuming that the charger is working at full power and (b) assuming that the car’s battery is in the right temperature range to accept full power. Neither are always the case.
So, we must come back to the question: which is the right battery for me? Or you? The answer is… not simple. Generally speaking, a low-mileage driver would probably be better off with a smaller LFP battery, while a regular long-haul driver would do better with a lithium-ion pack that can charge at 800 volts. As ever, there’s an awful lot of gaps in that answer.
And finally, what is kWh/100km and why should I care?
We had just become used to converting litres per 100km from miles per gallon (and sometimes back again, just to be sure) but now we have to get our heads around kWh/100km (kWh standing for kilowatt-hours).
This is the battery equivalent of fuel consumption, and is a rating of how quickly a given car will burn through its battery charge while driving. As with fuel consumption, there’s the official WLTP test that gives a car its equally-official figure.
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However, there’s a rub – as with fuel consumption, the official kWh/100km will likely be a best-case scenario, achieved in laboratory testing. Real-world driving is another thing.
How do you know if your car is performing well?
So far, the best and most efficient EVs will generally return about 17-18kWh/100km in mixed driving, including some motorway miles – always the hardest yards for any EV. If you drive predominantly in town you might see a little better – say 15kWh/100km – and the best we’ve tested has been the Hyundai Ioniq 6 which, thanks to its slippery body, managed to return an average of 16kWh/100km in mostly motorway driving. Anything over 20kWh/100km on average is generally considered to be fairly thirsty, while anything over 25kWh/100km is properly problematic on a longer journey.
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