EV - battery health

Mildly_Miffed

born_again said:

Mildly_Miffed said:

Sorry, but there's very few idiot yooochoobers that don't make me want to rip my ears off in seconds.

But if that's the Tesla video you mention (you can link, y'know), then it's entirely likely one that's covered as few as 3k miles in more than a couple of years is going to have degradation actually relating to that lack of use.

Extremely low mileage is VERY rarely good for cars, whatever they are.

Even then, you miss my point - which was "how long is a piece of string, because there's umpty seven different variables".

I know I can link, but it means a big link on the page.

Pasting a simple link like https://youtube.com/v/5dBqxv0PY3s takes up less space on the page than the description. (First vid for "tesla battery health" - no idea if it's the one you meant.)

As he is a Dealer, he is far from a idiot 👍

Mmmhmm.
No second-hand car dealers are idiots. Gotcha.
And they're all honest and trustworthy, too, right?

HillStreetBlues

MattMattMattUK said:

ElefantEd said:

EV batteries seem to be holding up much better than originally anticipated.

They are holding up in line with scientific predictions rather than the scaremongering amongst the anti-EV crowd.

That's incorrect. As knowledge increased the testing  and prediction changed with it, scientists now admit they got it wrong.
https://news.stanford.edu/stories/2024/12/existing-ev-batteries-may-last-up-to-40-longer-than-expected

Keep_pedalling

This video compares two 3 year old Teslas at the extreme ends of annual milage. Even the one used as a taxi with well over 200k milage on the clock still has plenty of life left in it the one with only 3k on the clock is almost as new at 99.5% capacity.

https://www.youtube.com/watch?v=1zM9mMBi9gw&t=755s

This is going to be the same with any EV with thermal management of the battery. 

Nasqueron

I've seen data on sites that a good battery in a good quality EV drops around 1% a year, even the lower end it's 1.8% or so. For the majority of drivers an EV is fine and the battery will outlive the car. Whenever the topic comes up, some card will pop up with their claim of driving 800 miles a day with 1 refuel or some nonsense that is nothing like the average UK driver - many people drive into cities as a commute, a huge chunk of our travel over distances under 1,2,5 miles is in cars and most will never need to drive hundreds of miles a day without stopping.

Martyn1981

ElefantEd said:

I would think that battery degradation would likely follow an exponential/log model rather than a fixed amount per year; so even if you lose 5% in the first year, you'd lose 5% of the remaining 95% the next and so on, so the actual reduction in range gets less and less. Though that might depend on whether the degradation is a question of complete cells failing or if it's a smaller reduction in lots at the same time.

Irregardless, EV batteries seem to be holding up much better than originally anticipated.

I think you are right, however there is another factor, and that's that BEV batts seem to see a drop in their first year, before settling down.

This may be as high as 5%, but from then on much smaller, perhaps 1%pa, depending on driving.

Most data seems to be available for Tesla's, simply because there are a lot of them, and they've been around for a long time, and as others have mentioned a drop of 10-15% over a longish period and 200k miles or so, seems pretty reasonable to me.

Totally agree with everyone about sellability. Someone buying a new BEV may want for example 300 miles of range. But the SH buyer typically expects a vehicle to be 'less good' than when new, and may well be buying it for a role where 250 miles is absolutely fine. And so on.


Just a note for folk, on something I doubled checked a few years ago, as I was unsure - a drop in battery capacity, isn't a drop in battery efficiency. So, if your SOH is now down to 90%, you will be putting in 'only' 90% of what you did when new. You won't still be filling it with 100% and only getting 90%. So it's more akin to a slowly shrinking petrol tank, than to a less efficient motor.

facade

My 3yr old 30,000 mile Citroen e-C4 shows 91.625% SOH (state of health), which has remained constant for the last 6 months (but I've only covered 1000 miles)

Comparing with the other boys & girls on the e-C4 group, this is pretty much the same as others get.

I'm hoping that keeping the charge between 40 and 70% and only charging at 4.6KW (20A) will help preserve it- I suspect that to do 29,000 in 2 years with a range of between 150-180 miles it did a lot of fast charging which quickly took it down..

Herzlos

Martyn1981 said:

Just a note for folk, on something I doubled checked a few years ago, as I was unsure - a drop in battery capacity, isn't a drop in battery efficiency. So, if your SOH is now down to 90%, you will be putting in 'only' 90% of what you did when new. You won't still be filling it with 100% and only getting 90%. So it's more akin to a slowly shrinking petrol tank, than to a less efficient motor.

That's a good point I hadn't really considered. I'd assumed it mean less efficiency but in reality it just means that bad cells aren't being used so the shrinking tank is a better analogy.

Presumably charging speed is largely unaffected too, so a 90% capacity battery will take 90% of the charge in 90% of the time?

facade

Herzlos said:

Martyn1981 said:

Just a note for folk, on something I doubled checked a few years ago, as I was unsure - a drop in battery capacity, isn't a drop in battery efficiency. So, if your SOH is now down to 90%, you will be putting in 'only' 90% of what you did when new. You won't still be filling it with 100% and only getting 90%. So it's more akin to a slowly shrinking petrol tank, than to a less efficient motor.

That's a good point I hadn't really considered. I'd assumed it mean less efficiency but in reality it just means that bad cells aren't being used so the shrinking tank is a better analogy.

Presumably charging speed is largely unaffected too, so a 90% capacity battery will take 90% of the charge in 90% of the time?

Yes.

The car displays charge as a % of useable capacity and the dashboard  GOM (guess-o-meter) will show a lower range at 100%, because 100% on the dash has now become less (90% of new).

The car will fast charge to 80% of its new lower capacity therefore in 90% of the time it previously took because it is charging to 80% of 90% .

A slow charge will take 90% of the previous time because the amount of charge lost/required has been scaled down accordingly.

Apparently what battery health certificates is going to fix is people are familiar with mobile 'phone batteries losing capacity at an alarming rate, and the same thing happens, they show 100% charge but there is only half the energy stored and they last half as long. (but charge up again quicker)

I'm not convinced tbh.