EV dilemma: faster charging or extended-range battery?
What’s the best solution? A 350 kW super-fast charger that can get you an extra 100 km after five minutes of charging, or a larger battery that gets you more than 500 km far, before having to charge half an hour?
It is an electric vehicle maker’s dilemma, these days, with European car manufacturers like BMW, Porsche, Audi and Jaguar rather in favour of the super-charger and Elon Musk of Tesla convinced of the need of more powerful batteries lasting longer.
DC current at 350 kW
A super-charger like the one Allego installed in Eindhoven (the Netherlands) last week can charge your car (if its equipped for it) with a DC current at 350 kW, some hundred times faster than when you charge with ‘home’ AC whole night long.
Five minutes charging time is almost as long as taking fuel today. So it won’t bother most drivers. Porsche, for example, claims its Mission E car to be launched later, will add 400 km in 15 minutes this way.
But Tesla CEO, Elon Musk, isn’t convinced that people want to ‘fuel’ every 100 km and believes it is better to have a range of 500 km or more with a powerful battery, even if that means you have to charge half an hour or an hour to get it back to 80% of its capacity.
Musk: ‘350 kW is ridiculous’
In May Musk said that super-fast charging is degrading the battery fast, and he calls the 350 kW European chargers ‘ridiculous’. Tesla itself limits its chargers today to 120 kW and might go as far as 200 kW in the future, not further.
“Musk surely as a point”, Peter Notten, professor battery technology at the Dutch Eindhoven University, says. Batteries today are good at slow-charging, but resistance increases when charging faster. Temperature will rise and if it goes beyond 45° C, the electrodes can break down and the battery loses capacity.
Won’t last for eight years
“Most electrical vehicle (EV) drivers have a lease contract or a company car for three years or more. So probably they won’t care about the batteries decaying”, Notten says. “But this way the battery won’t last for eight years.”
It is technically possible to ‘super-charge’ batteries, but for this the battery has to be built differently in a specific way, the professor explains. “When you charge a battery, in fact you’re pumping loaded lithium ions in it. Normally they spread out, but when quick-charging they tend to pile up at the poles and this causes wear.”
Who is to win?
“You can solve this problem by setting up the battery differently, but then you’re losing capacity, thus range”, Notten says. So it is a dilemma: you have to choose between building a car that can charge in five minutes, or one that can drive as far as possible. Unless new battery technologies emerge, it’s difficult to say which side will win in the future.