Electric cars are the future. But like petrol and diesel cars, they also have parts that wear out.
In this article, we consider the average lifespan of an electric car battery, how long they will last on a single charge, and what you can do to extend this.
What is the average lifespan of an electric car battery?
We know what you’re thinking - in an age of subscriptions and ‘early upgrades’, are EV batteries actually built to last?
On a related note, are EVs actually any better for the environment? We only have to look at the latest smartphones, which will typically only last for 2 years before the battery can no longer reliably hold charge and we trade them in for new ones.
Despite what you may think, EV batteries are actually surprisingly long-lasting. In most cases, they actually outlive the cars that they’re built for.
That’s because there’s a lot more room for sophisticated thermal management technologies (the same can’t be said for a paper-thin smartphone that lives in your pocket). In basic terms, the batteries are obviously much more powerful than the teeny ones we have in phones and laptops.
Although most current EV batteries will easily last for 400,000-500,000 miles, manufacturers are also experimenting with different battery chemistries, and it’s likely that we’ll soon have a ‘million mile’ battery, according to Tesla.
Why does an electric car battery lose charge?
Batteries lose charge through a process called battery degradation, where the amount of energy they can store and deliver permanently reduces over time.
A battery’s condition is called its State of Health (SOH). This is the ratio of the maximum battery charge to its rated capacity. For example, a 100kWH battery with 90% SOH would behave like a 90kWH battery.
Currently the most popular battery type is Lithium-ion. Time for a mini science lesson:
- Lithium ions are lost through side reactions with the electrolyte.
- Compounds are formed which “trap” free lithium.
- This reduces the number of Li-ions that can move between electrodes.
- The electrode structure becomes disordered over time, resulting in reduced battery capacity.
It’s worth noting that a vehicle’s electric range (the distance the vehicle can travel on those kWhs) does not necessarily reflect its SOH. Electric range can depend on a number of factors, such as charge level, temperature, driving habits, and passenger/cargo load.
What can affect electric car battery life and lifespan?
As we’ve already suggested, electric range is affected by a number of factors. But which factors have the biggest impact on a battery’s longevity?
Unlike petrol or diesel cars, the weather can have a big impact on how far an EV will go on a single charge. Too cold, and the rate of chemical reactions in the Lithium-ion battery is much slower, meaning longer charging times and less range. Too hot, and the battery will be put under increased strain.
Sure, you may not need to use your full range every day, but we’ve got some bad news for you if you live somewhere with a particularly hot climate.
A study by GeoTab compared battery degradation of EVs driven in hot climates (>5 days annually over 27’C) vs temperate climates (<5 days annually over 27’C). Vehicles driven in hot climates showed a noticeably faster rate of decline than those driven in moderate climates.
Maybe living in the cold, wet and windy UK isn’t so bad after all!
While rapid charging has helped many first time EV owners to overcome the dreaded ‘range anxiety’, it may not always be the best thing for your battery.
According to Kia Motors, “Frequent use of DC Fast Charging can negatively impact battery performance and durability, and Kia recommends minimizing use of DC Fast Charging”.
This certainly doesn’t mean you need to give it up for good. Manufacturers are always looking for new ways to prolong the lifespan of their batteries, whether that’s changing what EV batteries are made of, or implementing better thermo-regulation.
For example, recent research by Transport Findings has found that LFP (Lithium Iron Phosphate) batteries can charge at significantly higher ‘C rates’ than NMC (Nickel Manganese Cobalt) batteries without being adversely impacted.
Tesla recently announced a move to LFP batteries, which are also much cheaper to produce. Unfortunately, LFP batteries only have 65-70% of the energy density of NMC batteries, which could mean EV ranges increase more slowly in the future.
Draining the Battery
EV batteries are rated for a number of ‘cycles’. This is the number of times the battery will discharge 100% of its capacity. This does not mean that you need to fully charge and discharge your car to get the most out of it - a ‘cycle’ could start at 80%, and you may decide to recharge mid-cycle.
Charging and discharging a battery completely, from 0% to 100% (known as ‘deep discharge’), will degrade the battery performance much more rapidly than shallower discharge cycles with more frequent charging.
It goes without saying that the more you use a battery, the faster it will deplete. But what impact can high mileage have on the battery over the longer term?
In fact, a study by GeoTab suggests that over a period of 4 years, cars that were driven over 20,000 miles a year lost only 2.5% more of their SOH compared to cars that were driven less than 8,000 miles.
Of course, if you are doing this kind of mileage, it’s more likely that you’ll need to rely on the UK’s rapid charging network. This may explain some of the loss in battery capacity, so it’s always worth trying to minimise your rapid charging and use slow or fast chargers where possible.
How to extend your EV's battery life
EV batteries will inevitably degrade over time, but that doesn’t mean there’s nothing you can do to extend their lifetime. Some of the most important things you can do include paying attention to how you charge your electric car, and how often you charge your electric car.
1. Shallow charging (<90%)
EV owners will notice that their car’s battery capacity and ‘usable capacity’ are not the same. The Tesla Model S Plaid, for instance, has a battery capacity of 95kWh. However, the usable capacity is only 90kWh. This ‘buffer’ is to protect the battery from overcharging or discharging too much.
You can set the maximum charge your EV will accept and it’s recommended you set your maximum charge capacity to around 90% to protect the battery.
‘Shallow charges’ like this also mean you’ll be able to make the most of regenerative braking (and reduce unnecessary brake wear), which is usually disabled when the battery is fully charged.
2. Charging before the battery is depleted (>20%)
At 396 miles on a single charge, the Model S Plaid may have the most impressive electric range on the market, but that doesn’t mean you should be constantly pushing it to its limits.
Keeping your EV charged so that it doesn’t fall below 20% is a smart way to prolong the life of its battery.
3.. Minimise rapid charging
Rapid charging is advertised as a key feature in newer EVs with bumper batteries. In most cases, it means the hours-long wait to recharge your car could be cut down to just 30 minutes or less - just enough time to grab a coffee.
Unfortunately, it’s not without tradeoffs. Aside from the often inflated price, rapidly charging a battery means high currents and, as a result, high temperatures. This can put a strain on the battery, which is even greater when the ambient air temperature is already high.
If you are able to, charge your electric car at home, or with slower EV charger types. AC charging at home is much slower, but will put less strain on your battery. If you’re concerned about how long it will take to charge an electric car without rapid charging, try to plan your charging around times when you know the car will be idle (overnight, or from 9-5pm, for example).
4. Don’t leave it for a while on zero or full charge
If you don’t plan on using your EV for a while, it’s a good idea to not leave the battery empty or fully charged. Both states can place increased stress on the battery.
Most manufacturers recommend leaving the EV stationary with a State of Charge (SOC) between 30-75%. This takes into account ‘vampire drain’, which is the amount of charge the car loses when it’s sat idle for a long time.
All lithium-ion batteries self-discharge when not in use, but EVs also use sophisticated battery management processes when idle. Therefore, it’s a good idea to ensure that your EV battery will not run down to zero when not in use.
One way to do this may be to park your EV in a shaded spot, or garage, so that the car’s thermal management systems don’t need to kick in to keep the battery at the optimum temperature.
Do manufacturers provide a warranty on electric car batteries?
Yes, most manufacturers provide a warranty on the battery based on years owned or miles driven. Typically, this is between 5 and 8 years and 80,000- 125,000 miles. For example, a Mercedes EQC comes with a battery warranty that covers you for 8 years, or 100,000 miles, whichever comes soonest.
However, battery degradation is a given and you won’t be able to make a claim on your warranty for any loss in performance. For example, the Mercedes EQC has a ‘minimum allowable capacity’ of 70%, which means if your battery still holds 80% of the charge it did when it was first purchased, you can’t make a claim.
What if I lease my battery?
If you leased the battery under a separate agreement (a popular choice with people who buy electric cars like the Renault Zoe and Nissan Leaf) the battery will be replaced or repaired free of charge if it’s found to have degraded.
All cars degrade over time - electric cars are no exception. But should you be worried about how long electric car batteries last? Probably not.
Battery technology has come on leaps and bounds in recents years, offering longer ranges, better thermal regulation, and reduced lifetime degradation - and with an ever-expanding network of public chargers, you’ll never be far away from a charger if you need it.
Of course, battery degradation is just one small part of owning an electric car, and there’s a lot to weigh up if you’re considering whether or not you should buy (or lease) an electric car now or wait. Check out our electric car pros and cons to help you decide.