Research reveals the truth about electric car battery degradation

Published 26 November 2019

Electric cars lose just one per cent of their battery capacity per year due to degradation, new research claims. 

Electric vehicles account for just over two per cent of all new cars sold in the UK, but are expected to increase in popularity as buyers look to replace their diesel and petrol vehicles with low-emission alternatives.

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However, while the technology behind electric cars has seen significant improvements when it comes to range and cost, some buyers are concerned about the longevity of the tech and the impact of battery degradation.

Indeed, readers frequently contact HonestJohn.co.uk via Ask HJ to find out how long an EV's battery will last before it wears out and requires replacement. However, new research, carried out by Plug In America and analysed by NimbleFins, reveals that a typical Tesla Model S will have 93 per cent of its original battery capacity after seven years - suggesting it loses just one per cent a year.

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Battery degradation is affected by how many charge cycles it's been put through (i.e. how many times it's been charged). Cars with higher mileages will have been charged more, so the battery will have degraded more. The research reveals that the average Tesla Model S battery provides more than 90 per cent of its original range up until around 150,000 miles. After that, the range starts to noticeably drop off.

The car with the highest mileage in the survey was a Model S 85P with 232,442 miles on the clock which could cover 220 miles on a charge - 83 per cent of its original 265-mile range.

While the survey concentrates on the Model S, anecdotal evidence suggests batteries in other electric cars might last just as long as those in Teslas. One HonestJohn.co.uk reader reported covering 160,000 miles in a Nissan Leaf over three years without an issue.

Generally, manufacturers advise that EV batteries are intended to last the lifespan of the car. Nissan, for example, provides an eight-year, 100,000-mile warranty for the battery in its Leaf, while the Hyundai Kona Electric comes with an eight year, 125,000-mile battery warranty. If the battery drops below a certain capacity in this time, the vehicle manufacturer says it will be replaced with a new one at no cost. 

Comments

   on 26 November 2019

That's only half truth. Batteries degrade 1%/year by simply existing only.
Also Tesla has the best chemistry in their batteries in terms of durability and reliability. All other EV have different chemistry compared to tesla-panasonic. All will degrade faster than Tesla

De Sisti    on 26 November 2019

[quote]That's only half truth. Batteries degrade 1%/year by simply existing only. Also Tesla has the best chemistry in their batteries in terms of durability and reliability. All other EV have different chemistry compared to tesla-panasonic. All will degrade faster than Tesla[/quote]

Do you have any evidence, or links to prove this?

Edited by De Sisti on 26/11/2019 at 16:31

DeadBat    on 26 November 2019

Wondering how much power on average will ICE car loose after 7 years.

Keith Moat    on 2 December 2019

Battery degradation is about capacity not power. An ICE car will not lose any capacity, it's fuel tank doesn't shrink.

VINCENT MILLARD    on 3 December 2019

But it will use more Fuel.

paulj56    on 2 December 2019

The difference is an ice will still cover the mileage it's tank will allow, will an ev, I doubt that very much every chargible battery degrades, and what is so environmentally friendly regarding the production and disposal of these toxic batteries, and was is so green about now saying the life span of a car with batteries is now 8 years, the battery replacement alone will be more than the car is worth.

The_Rev    on 2 December 2019

you wrote an ICE will still cover the mileage its tank will allow ; was not the point when new it did 450 miles on a tankful and after 10 years perhaps only 350 ; numbers for example purposes only

The_Rev    on 2 December 2019

interesting point ; I have an Audi A8 with 112,000 7 years old which I think is still very close to 100% ; but how to quantify % loss ; good point

Engineer Andy    on 26 November 2019

I also wonder if the 'report' mainly covers where most Teslas reside, i.e. in warm, sunny California, where battery degridation and range is likely far less affected by the weather - low ambient temperature and higher drain caused by poor weather will surely have a negative affect.

MoDo613    on 27 November 2019

On the contrary. Cooler climates are better for batteries, so sunny California will have put the batteries through a worst case scenario. Higher drain isn't an issue as the 'C' rates (charge/discharge rates) are carefully matched between pack sizes and power draw.

Engineer Andy    on 28 November 2019

On the contrary. Cooler climates are better for batteries, so sunny California will have put the batteries through a worst case scenario. Higher drain isn't an issue as the 'C' rates (charge/discharge rates) are carefully matched between pack sizes and power draw.

I thought it was well known that in cold climates, like in cold weather, battery efficiency drops and thus they need charging more often (as well as because they need to be used more, e.g. for heating) and thus how long they last in such climates is far lower than in warmer ones (even accounting for the use of A/C). Recharging more often reduces battery life.

MoDo613    on 28 November 2019

Indeed you are correct, the batteries are less efficient and drain for heating is higher in cold climates/weather. However degradation has only been observed to have a damaging effect due to very high temperatures. So in winter whilst range will be reduced (same as for petrol or diesel - only more noticeable due to the lower density of energy store held in the car) the battery hasn't actually suffered. In theory more charging cycles are damaging, but thats only full cycles from 0-100% and no EV allows full use of a charge cycle ever, its only ever a band well inside the 0-100% range (for example 60% useable capacity in the case of 1st gen Chevrolet Volt). Small cycles are potentially beneficial for the battery health overall in fact. See for example this study www.sciencedirect.com/science/article/pii/S0360544...#!

paulj56    on 2 December 2019

My diesel seems to love the cold dense air that enters it, I travel 50 miles to work 5 days a week and I never go below 70 mpg hot or cold

Ted Tomlin    on 3 December 2019

Agreed batteries don't like the cold.

   on 26 November 2019

There's never any coverage is there about how combustion vehicles "degrade" in a multitude of ways - no mention of the fact that most combustion vehicles are considered either ready for the scrapyard after 150,000 miles or not sell-able for more than £2000-4000 - no matter what the original price may have been and no matter how many $thousands may have been blown on ICE maintenance and repairs over the years.
Paul G

DeadBat    on 27 November 2019

There's never any coverage is there about how combustion vehicles "degrade" in a multitude of ways - no mention of the fact that most combustion vehicles are considered either ready for the scrapyard after 150,000 miles or not sell-able for more than £2000-4000 - no matter what the original price may have been and no matter how many $thousands may have been blown on ICE maintenance and repairs over the years. Paul G

Agree, ICE engine after 150,000 miles is considered to be almost at the end of its life.

Mino    18 hours ago

I'd say that a car with 150k on it is "worthless" because by then it's knackered..

However it's more likely that worn out transmission, suspension, brakes and exhausts etc. are the hight cost items that generally make them undesirable.. not to mention that it'll be 15 years old, so the interior will be worn, faded and just plain old fashioned. The engine itself will be the least knackered component, if it's been serviced anywhere near regularly.

Edited by Mino on 27/01/2020 at 11:37

paulj56    on 2 December 2019

150000 miles and done for,, look at the mileage of any taxi it ranges from either a new taxi up to 400000 miles my old panda multi jet had 220000 on the clock when it was sold on and it is still on the road, and all that car cost me was a radiator that had a stone through it and a turbo through Fiat warranty

   on 27 November 2019

Probably true for a big battery doing 300miles per charge in Sunny California.
Lithium batteries will be seriously degraded after 1000 full charge which in the case of a Tesla is around 300k miles (which is why Tesla claims in the first place). Buy a second hand Leaf or Zoe with a 22kwh battery who spend its time in cold England and it might be a different story... Worst, get a plug in hybrid with a small battery that is being constantly charged and emptied on a daily basis and you're in for a bad surprise quite early in the life of the car... Car maker should be more upfront about the estimated longevity of their batteries.

MoDo613    on 27 November 2019

Except ex Nissan Leaf taxis with 170k miles sell for roughly double an equivalent Focus with half the mileage sells for of the same age. Ebay history can confirm this as does my own experiance. Reason being, the batteries do not suffer practical degradation even after mileages that decimate ICE cars. The drivetrains similarly are so durable the existing dealer network system built on warranty, servicing and repairs is under serious threat. Why do you think Kia banned its dealers from selling EV's until the EU penalty deadline?!

PHEV's like the Chevrolet Volt/Ampera use only 60% battery SOC for a full 'cycle'. This is why despite large numbers sold in the US there have been no batteries replaced for degradation! In fact these cars still have full factory range after 400k miles - one particular such car is known worldwide as Sparky (google it). Please stop believing the naysayers, anyone who's owned an EV or proper PHEV loves it and looks at ICE cars as history.

The only ones in for a surprise are those still buying expensive diesel or petrol cars of which values are likely to plummet (more than they do already) when the fossil fuel funded EV deriding campaigns start to be seen as the lies they are. But yet some people still believe OneCoin is going to make them rich!

Edited by MoDo613 on 27/11/2019 at 23:31

madf    on 29 November 2019

Anyone quoting a US survey on only one make (and a top range model as well) and using it as applicable to the UK is either naive or disingenuous.

willywonker    on 30 November 2019

We bought our 1st Toyota Prius in 2001.
What a wonderful smooth and easy drive. Brilliant car, nothing else like it at the time.
At 40,000m in 2010 we sold it to a friend and replaced it with a second generation Prius which we still have with 50,000m on the clock.
Our friend still owns and drives our first generation Prius, which is now 18years old. This year the battery gave out but has been replaced at £1700.
This equates to approx £100 p.a. battery depreciation cost or around £2 per week.

jchinuk    on 2 December 2019

While your experience of the Prius is positive, judging by the Prius minicabs locally, they are driven so fast they are running on petrol most of the time anyway. There are also apocryphal of people buying second-hand plug-in hybrids and finding still wrapped charging leads in the boot.

willywonker    on 2 December 2019

Yes I have heard reports of plug in hybrids never being plugged in.

Our Prius is not plug in. As a matter of interest our recorded mpg is 49mpg in the Winter and 58 mpg in the summer.

Lee Hutchins    on 2 December 2019

Prius batteries - a Taxi driver in Southampton told me they get exchange batteries for around £400, they may not be genuine but cheaper alternatives are out thee (170,000m car that I was in)

Model Flyer    on 2 December 2019

Lithium batteries DO degrade . Look at power tools, tablets or virtually any cordless device you can think of . An EV will probably last reasonably well if its used regularly but low mileage cars will suffer from battery degradation unless they are parked up with a the battery discharged to the Storage charge (approx 30% charge ). The downside as far as I can see is when nearly all cars are electric and charging becomes a problem as we or the national grid just doesn't have the capacity to charge them at peak times like in the evenong when we get home ,and certainly not Fast Charge as many makers are boasting about as this can take a hefty 3Kw and even then only gives a 40% charge after an hour or so . You wont be able to drive the distances we have become used to and society WILL have to change its ways and use Publiic transport more : but is there the capacity to to do that ? Those green lovies should look at the way lithium is sourced . It ruins large ares of land and they don't give a damn about the people who have to live in those areas.. EV are very green at point of use but look back down the trail and the polution is just as bad .

Edited by Model Flyer on 02/12/2019 at 17:09

VINCENT MILLARD    on 3 December 2019

That's only half truth. Batteries degrade 1%/year by simply existing only. Also Tesla has the best chemistry in their batteries in terms of durability and reliability. All other EV have different chemistry compared to tesla-panasonic. All will degrade faster than Tesla

Come on evidence is needed. I worked in the Electronics Industry for 45 Years and Laterly with Li-Ion, They don't degrade like all other types. Also All Li=Ion Batts Have very much the same Makeup, unless you are privy to a Miraculous new design that Tesla have.

Even if they do degrade slightly Quicker due to differing conditions, the Batts still last longer than the Life of any Car, Van, Bus or HGV.

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