Editor’s letter: Bigger no longer better for EV batteries
The BMW iX's battery – at slightly more than 100kWh – provides a real-world range of around 250 miles
Balancing what's perceived as a 'good' battery size with efficiency is a new challenge for manufacturers
The electric car world is moving apace, and so are the language and reference points we use. Not only is there range (still expressed in good old-fashioned miles), but also battery size (kWh). Then there’s efficiency (miles per kWh), charging speed (kW), and now also the consistency that speed is delivered.
Most important at the dawn of the electric era was range, and to this day electric cars are largely marketed around that number. Range has typically been dictated by battery size, but now as efficiency improves, battery size becomes less relevant. A larger battery actually hurts efficiency, as the car is heavier.
“My personal sense is that bigger is seen as better” when it comes to battery size, according to Nissan’s European R&D boss David Moss. “If you buy with range in mind, you pay a lot more money and you add weight to the car,” says Moss. “If 75% of your miles are in town, you’re just carrying extra weight and hurting efficiency.
“If your goal is to have the most efficient EV, then you use the smallest battery. It can be confusing.”
Clearly no car maker is going to go for that; it would be a nightmare for the marketing department. So the optimum size, type and chemistry of battery to make a car useful and usable to a customer will consider “how far you have to drive, and how quick you can charge”, according to Moss, and it’s not just charging speed but the consistency of speed that is likely to become the next dominant number in the electric car lexicon.
Key to car makers will be “balancing the range and the ability to charge”, and for customers “to get a stable amount of [charging] power, not something that peaks and drops off. They want reliability, and if it says it’ll charge at that speed it charges at that speed”.
I’m speaking with Moss in the deep south of Belgium, having travelled here in a BMW iX. Its battery is vast, at just over 100kWh, and I can expect a range of about 250 miles on the types of roads and speeds that stand between me and my 400-plus-mile drive home to Berkshire. He asks me what I’m looking for when it comes to charging on the way home (the iX can charge quickly, at speeds of up to 190kW), which I’ll have to do.
Stop once, I say. “And you want to stop for as little time as possible,” Moss adds. Which brings the conversation back to the amount of miles you drive versus the speed at which you can recharge. He believes home charging, and 22kW AC charging when out and about in public car parks like supermarkets covers off most of the charging needs people will do, and “only use highway charging when you need to” on journeys such as the one awaiting me.
“On a long run you’ll need it, and you’ll want to stop for the toilet or a coffee anyway. But for how long? How do we get to that optimum number of 15 minutes? Most would be happy with that, and you can get into a habit of that working, like with an F1 splash-and-dash. You just want to get to the end of the race,” says Moss, adding that at double the cost of charging at home, you’re not going to want to make a habit of charging on the DC motorway charging network anyway. Once that time and expectation is set at 15 minutes, the car needs to deliver the consistent range of charge to support it.
What’s optimum, then, in balancing battery size with efficiency and charging speeds? In the future, it sounds very much like the solid-state batteries Nissan will have with us by 2028, halving costs, doubling energy density and trebling charging speeds versus today’s lithium-ion batteries.
In the meantime, “it’s innovation again”, says Moss, “not just with the battery but its ability to take power, and not with the size of the charger but the ability to take charge”.
We’re beyond range anxiety - and past the first stage of charging anxiety (being able to find a charger to charge an EV). And now comes part two of charging anxiety: the worry over the speed at which it is able to charge when we’re plugged in.
As Moss admits himself, it is confusing, and you’d be forgiven for thinking as much. Like so much in the ever-changing world of electric cars, charging speeds and consistency are a learning and education job, and car makers as much as customers need to do their homework.