Do they keep going and going?
Batteries in cars may last a lot longer than the sort of batteries found in your phone or laptop, but how much longer?
While it is true that electric cars lose battery capacity over time, the continuing advances in technology mean the precise degradation is difficult to define as a whole. The main factor is all down to the owner and how they treat the battery: the way energy is added, the way it is removed and how many charging cycles the battery experiences.
It isn’t uncommon to see Teslas or other electric cars with 100,000-miles on the odometer and experiencing battery degradation of less than 10%. Meet Wizzy, for example, a Nissan LEAF taxi from England that clocked up more than 170,000-miles on its original battery before being sold to another happy owner.
So there are a number of factors that help batteries stay healthy.
The first may seem slightly counter-intuitive, but lithium batteries don’t like to be fully charged. That’s because heat is the enemy of battery systems and lots of heat is generated by both rapid charging and keeping the battery at high-voltage. While batteries like to be cycled and used, the general rule is not to be too reliant on rapid chargers, nor to overcharge the battery or let it go completely flat.
The risk here is that dendrites can form, which are like weeds in the garden of battery chemistry and can cause failure. Instead, it’s advised that owners should always try to drive and charge their EVs in that happy middle ground between 20 and 80%. That’s because heat is the enemy of battery systems and lots of heat is generated by both rapid charging and keeping the battery at high-voltage.
Lots of heat is also produced if you like showing off to your friends how quickly your electric car can accelerate from a standstill. When you select Ludicrous+ Mode on a Tesla, it actually warns you that you’ll be impacting the battery life.
Fortunately, most electric cars are fitted with sophisticated battery management systems that can regulate power if you’re doing too many drag races, as well as create artificial buffers at the top and bottom of a battery’s capacity - to ensure cells in the battery pack don’t overcharge or over-discharge.
Battery management systems in performance EVs like the Porsche Taycan, for example, can even work with satellite navigation, so it knows to pre-condition the battery when approaching a charging station.
Ambient temperature is another factor that needs consideration, because extremes of heat and cold can negatively impact a car’s battery life. This is where battery packs that feature active thermal management degrade less than those that rely on air cooling, because they’re better at maintaining a stable temperature range for the battery.
Carmakers are well aware that potential buyers are concerned about the longevity of electric car batteries, which is why these specific warranties often far exceed a typical vehicle warranty. There’s no better example than the new Lexus UX300e, which is the first vehicle to feature a 10-year, 1 million kilometre warranty on the battery pack. If that’s not confidence in the technology, we don’t know what is.