EV battery degradation - what does it really mean?

Forums › Transport (cars, bikes and boats) › EV battery degradation - what does it really mean?

insane

3236 posts

Uber Geek

ID Verified

Trusted

#302792 20-Dec-2022 23:33

If an theoretical 100KW EV battery degrades to 80% SOH, does it mean that you're still having to charge it with 100KW worth of electricity to fully charge it, or is it's capacity simply reduced, meaning the battery will only take 80KW but still appear to be charging to 100% on the energy gauge?

Asked differently, is the SOH a reflection of remaining battery capacity from new, or do degraded batteries give off say more heat or something which reduces their effective range/capacity?

michaelmurfy

meow
13240 posts

Uber Geek

Moderator

ID Verified

Trusted

Lifetime subscriber

#3012612 21-Dec-2022 00:41

Capacity is reduced so it'll take less energy to charge as it stores less energy. But just also note this isn't really as much of a thing as it used to be.

With the Nissan Leaf the battery was passively (air) cooled and the batteries would cook during DC Fast Charging. Newer cars have liquid cooled batteries so they don't cook themselves + degrade too quickly. Essentially, the battery -should- out-last the actual car.

Bjørn Nyland on YouTube does a whole lot of tests but his Model S P85 is an absolute tank and really has not degraded too much in its years of service. Battery technology has gotten far better since (especially with LFP batteries) so battery degradation on modern EV's is really a thing of the past:

Michael Murphy | https://murfy.nz
Referral Links: Quic Broadband (use R122101E7CV7Q for free setup)

Are you happy with what you get from Geekzone? Please consider supporting us by subscribing.
Opinions are my own and not the views of my employer.

Batman

Mad Scientist
29760 posts

Uber Geek

Trusted

Lifetime subscriber

#3012613 21-Dec-2022 00:47

OP do you have a mobile phone or laptop?

after a while charging to 100% gives you less screen on time

Batman

Mad Scientist
29760 posts

Uber Geek

Trusted

Lifetime subscriber

#3012614 21-Dec-2022 00:54

to be precise it's more complicated.

many manufacturers trick you. i'll give one way they do that.

say the EV has 80khw battery.

when you buy it they advertize 75kwh.

the software when you charge to 100% it stops at 75kwhr and it makes scary graphics at 20% and don't let you drive at 5% which corresponds to 15kwh.

so you are only getting 75-15= 60kwh

as the battery degrades the software manages the range by only allowing you to use 60kwh anyway.

when the battery degrades from 80kwh to 62kwh after 8 years you don't realise anything and you tell everyone the car is amazing same range after 8 years.

but really you were tricked.

insane

3236 posts

Uber Geek

ID Verified

Trusted

#3012736 21-Dec-2022 13:42

Batman:

to be precise it's more complicated.

many manufacturers trick you. i'll give one way they do that.

say the EV has 80khw battery.

when you buy it they advertize 75kwh.

the software when you charge to 100% it stops at 75kwhr and it makes scary graphics at 20% and don't let you drive at 5% which corresponds to 15kwh.

so you are only getting 75-15= 60kwh

as the battery degrades the software manages the range by only allowing you to use 60kwh anyway.

when the battery degrades from 80kwh to 62kwh after 8 years you don't realise anything and you tell everyone the car is amazing same range after 8 years.

but really you were tricked.

So a bit like how SSD's are overprovisioned to allow for a certain amount of blocks to go bad, but not effect overall capacity - okay makes sense, and while sneaky, quite smart on their part.

Getting pressure from the wifey to sell our aging 2nd car and get a ~2017 Leaf for going to the shops etc. Just wanted to make sure I wasn't misunderstanding how it really works, especially given some of the stories I've heard about Leaf batteries in particular.

jonathan18

7413 posts

Uber Geek

ID Verified

Trusted

#3012793 21-Dec-2022 16:03

insane:

Getting pressure from the wifey to sell our aging 2nd car and get a ~2017 Leaf for going to the shops etc. Just wanted to make sure I wasn't misunderstanding how it really works, especially given some of the stories I've heard about Leaf batteries in particular.

In the end, even with the risk of fairly significant range reduction, a Leaf will work perfectly in that kind of situation (unless 'going to the shops' is still a significant journey!).

As an example, my wife's 2013 Leaf is down to a range of around 100km (urban - way lower on open roads), having started at 145km when we bought it four years ago. It too is our 'second car', so the most it needs to do on a daily basis is typically 10-20km, with a very occasional 30-40km trip. On this basis, even if it continues to degrade at the same rate it'll still meet our needs for at least as long again.

The only dilemma we've hit is that my wife's not keen on driving my own recently purchased car on longer trips by herself, given her own car won't work for such trips; in this case, we may have to see if she can swap cars with a family member.

Batman

Mad Scientist
29760 posts

Uber Geek

Trusted

Lifetime subscriber

#3012814 21-Dec-2022 18:10

insane:
Getting pressure from the wifey to sell our aging 2nd car and get a ~2017 Leaf for going to the shops etc. Just wanted to make sure I wasn't misunderstanding how it really works, especially given some of the stories I've heard about Leaf batteries in particular.

Leaf is not that smart.

Range just goes down.

They don't hide anything. They don't manage anything.

I was taking about the latest EVs that have these tricky software built into them.

GV27

5896 posts

Uber Geek

#3013387 23-Dec-2022 08:43

It will vary from vehicle to vehicle. But in general, charging an already-hot battery will damage it. It also takes a long time for batteries that are hot to cool down if they do not have active cooling. Think 'overnight', not minutes. That's why the Leaf will rate-limit on back-to-back DC charging sessions in the same day. The heat will also impair the performance of the battery over time; this is where 'degradation' is mostly focused on with the Leaf.

But any Lithium Ion battery will degrade, and in some cases that's a function of time as much as usage. That's a factor in degradation as well.

If you like reading about battery developments, researchers talk about 'cycles' in a laboratory context, which is usually a 100% charge and then discharge down to zero. It's not likely that any modern EV BMS would ever allow that to happen, so the batteries that perform well in lab tests are generally withstanding some pretty brutal usage. So 'degradation' in that context is something entirely different.

Getting those promising chemistries and tech to scale from a small button or pouch to a commercial cell that can be produced on existing manufacturing lines is where most battery 'advances' seem to falter. LFP is getting better all the time and seems to be providing big improvements in densities at lower costs, on an already pretty resilient chemistry. It's a high bar for anything new to get over.

Equinox IT

Cloud spending continues to surge globally, but most organisations haven’t made the changes necessary to maximise the value and cost-efficiency benefits of their cloud investments. Download the whitepaper From Overspend to Advantage now.

Batman

Mad Scientist
29760 posts

Uber Geek

Trusted

Lifetime subscriber

#3013709 24-Dec-2022 02:32

slightly off topic

- some people might get caught out so it's good to know

there are cars that 0-100% on the software scale display is not a Linear measure

100-80% might give you more juice (kms) than say 40-20% might give you less range.

other trick for newbies is - some cars the estimated range is accurate, some not accurate - such that if you relied on those you might get stuck with a flat battery

you need to know your car.

it's a bit too much for an old fart like me, i used to flash ROMs on my samsung and this is the type of people who would really do well with figuring these things out on EV. right now i just want to drive and not think about range.

unspecified

19 posts

Geek

#3026540 24-Jan-2023 18:29

I'm prepared to say there's very little degradation in a well-managed battery, such as -- in my personal experience -- a 2017 or 2018 Hyundai Ioniq, and later.

My 28kWh (usable) battery will still charge to a range of 225km, as new.

(The dashboard guessometer range varies slightly from time-to-time as it reacts to my driving history; 215-228km, and, yes, it will do that distance.)

The canIoniq phone app that connects to a BlueTooth standard plug-in device in the OBD port and does the LeafSpy equivalent shows my 4&1/2 year old Ioniq, at 90,000km, has the same battery capacity you'd expect in a nearly brand new battery. EG: individual cells are consistent and show a cell voltage of 4.02v at 95% charge, out of 4.2v max.

There's a YT video where a UK Ioniq owner inspects his 2017 Ioniq that has done 100,000 *miles* (160,000km) and it shows the same, and he discusses how the high and low buffers work, and how these haven't been used yet. He runs through his more sophisticated device and explains what it shows the car reporting.

The video, one of several about various EVs: https://www.youtube.com/watch?v=ybw9B4NbHLM

Batteries, except for Leafs (afaik), seem pretty bloody durable.

Cheers.

Batman

Mad Scientist
29760 posts

Uber Geek

Trusted

Lifetime subscriber

#3026670 24-Jan-2023 20:50

unspecified:

I'm prepared to say there's very little degradation in a well-managed battery, such as -- in my personal experience -- a 2017 or 2018 Hyundai Ioniq, and later.

My 28kWh (usable) battery will still charge to a range of 225km, as new.

(The dashboard guessometer range varies slightly from time-to-time as it reacts to my driving history; 215-228km, and, yes, it will do that distance.)

The canIoniq phone app that connects to a BlueTooth standard plug-in device in the OBD port and does the LeafSpy equivalent shows my 4&1/2 year old Ioniq, at 90,000km, has the same battery capacity you'd expect in a nearly brand new battery. EG: individual cells are consistent and show a cell voltage of 4.02v at 95% charge, out of 4.2v max.

There's a YT video where a UK Ioniq owner inspects his 2017 Ioniq that has done 100,000 *miles* (160,000km) and it shows the same, and he discusses how the high and low buffers work, and how these haven't been used yet. He runs through his more sophisticated device and explains what it shows the car reporting.

The video, one of several about various EVs: https://www.youtube.com/watch?v=ybw9B4NbHLM

Batteries, except for Leafs (afaik), seem pretty bloody durable.

Cheers.

can you tell us your charging habits?

do you charge to 100%? how often do you charge? how low do you let your battery % get when you plug it to charge?

how many kms does the car have? is it parked in the garage? which city are you in?

[PS - without finding out the software buffer management/trickery when new vs now - as I explained at the top, it's hard to know that your battery "has not degraded" - not saying I don't believe you, we just don't know]

unspecified

19 posts

Geek

#3026674 24-Jan-2023 21:13

The car has done 4000+ charge cycles.

It used to be purely charged on HV charge points before I bought it, recently.

I've told you the kms.

I charge mostly at home now, perhaps one in four at a fast charger -- they're [relatively] expensive.

I'm trying to train myself out of plugging it in every time I get home, because I understand it's better for the car to let it run down a bit.

I don't normally let it drop below 30% charged.

I'm not going to bother with garage & city, but the climate is moderate.

There is no reply I can give that will convince you, other than to mention that my experience mirrors many other peoples'.

____________________________________________

can you tell us your charging habits?

do you charge to 100%? how often do you charge? how low do you let your battery % get when you plug it to charge?

how many kms does the car have? is it parked in the garage? which city are you in?

Batman

Mad Scientist
29760 posts

Uber Geek

Trusted

Lifetime subscriber

#3027629 26-Jan-2023 17:49

6 yr old 160,000km at 100% SOH