Battery degradation

liamog

We've had quite a few threads around here bring up battery degradation.
Seems it's either been Leaf owners defending Nissan's degradation versus everyone else.

I figured a thread where I could share my current understanding (and no doubt correct it was in order).

Battery Degradation is a perfectly normal behaviour of Lithium Ion batteries. Over time the battery can hold less charge. We've all probably seen this with our smartphones. The main factors that affect degradation are, the depth of discharge (from x to y %), the number of cycles (times charged from x to 100%), the speed of the charge (expressed in a C rating), and the temperature a battery is held at. Battery degradation is commonly measured by a so called State of Health (SoH). State of Health does not have a formal definition, but is generally expressed as a percentage Current Capacity / Initial Capacity.

unkel

Nice thread. This contribution might surprise some. If you keep a Lithium Ion battery in perfect conditions, that is cycle it only between 25% and 75% and keep it at 21C at any time, it will last 50 years at one cycle a day and still have about 70% capacity at the end.

liamog

Kia and Hyundai sell their cars with a usable capacity. The original Kia Soul was sold as a 27 kWh model, the actual battery was 30.5 kWh. Similarly the Hyundai Ioniq is sold as a 28 kWh battery, however in reality it has 30.96 kWh.

Nissan have been selling their cars with a total capacity, the original 24 kWh Leaf had a total capacity of 23.4 kWh, the current 40 kWh model has 39.46 kWh.

I found this great graphic which shows how total capacity reduces over time. For manufacturers that sell as usable capacity they can take advantage of this to claim a SoH of 100% for the first few years. The end-of-life in this image refers to the time that usable range starts to drop.



Kia for instance report their state of health using current total capacity/initial usable capacity. In this case day one of driving the car will have a SoH of 112%. The Kia BMS does not report a SoH figure, but others have calculated one using other figures, they were able to confirm via a dealer report, that any number above 100% is rounded down to 100%. If this is the same for Hyundai it likely explains why we see 100% returned by the BMS for cars that are nearly three years old.

SlowBlowin

A nice technical thread.

Battery care is a weekly chore for me (lead acid) and understanding a cell chemistry likes and dislikes is important. In the consumer marketplace this must be done automatically for the user by the manufacturer, hence on passively cooled EVs we see the wide variation in reported degradation as the users behaviours can have a greater effect on the cells.

Other manufacturers who employ active cooling see a much tighter curve of degradation reports.

Manufacturers are pushing the envelope of charging rates too, which can be a battery killer.

I think if you buy an actively cooled EV now, limit fast charging rates, and keep it between 20% and 80% the battery should out last the car.

handofdog

Interesting!

My car (gen 1 24kWh leaf) has an SOH of approx 65%.

Should I still try to keep the SOC between 25% and 75/80% of the existing (approx 15kWh) capacity?

This will mean a higher number of actual charges. This could result in 50% more charges - i.e. charge every 2nd day rather than every 3rd.

Current estimate range is 100km which is realistically 85 and my daily commute is approx 20km all in so I was trying to eke out 3 days rather than charge every 2nd day.

Any advice appreciated. Cheers.

liamog

From the datasheet for the Ioniq battery cells (https://shop.envites.de/images/pdf_my/LithiumIon43.pdf), using a 100% depth of discharge the Ioniq cells are good for around 600 cycles before they hit 90% capacity. If my position on how Hyundai report SoH is correct, that means the car should be able to supply the equivalent of 600 full charges before we start to see any drop in SoH or apparent usable range. Using the rated efficiency of 15.6kWh/100km means an Ioniq should be capable of around 107,000 km.

liamog

handofdog wrote: »

Current estimate range is 100km which is realistically 85 and my daily commute is approx 20km all in so I was trying to eke out 3 days rather than charge every 2nd day.

Any advice appreciated. Cheers.

Sounds like you need 25% of your current usable battery for your daily needs. To get the best life out it, you would be better charging every day to 65%, and using it down to 40%. In reality life is too short for that so I'd keep the charge limit at 80% and charge every other day.

OH the irony, all the abuse I got when I suggested people take better care of their batteries, like not charging to 100% if People didn't need to, watch the heat etc.

Oh but Nissan knew better than me and that's why the Leaf has a BMS ! lol

listermint

[Deleted User] wrote: »

OH the irony, all the abuse I got when I suggested people take better care of their batteries, like not charging to 100% if People didn't need to, watch the heat etc.

Oh but Nissan knew better than me and that's why the Leaf has a BMS ! lol

You must have missed the third post.


Nissan are no champions in this .

NIMAN

Since I bought my 2014 Leaf a couple of years ago, I have always charged to 100% every night.

I like the idea of having a 'full tank' at the start of each day, just in case. Usually the battery would be down at 40%-65% at the end of the day. I'd rarely see my battery down in the teens or 20s before charging starts again.

I still have 12 bars, but since I now have a work charger I might start charging overnight to 80% instead of 100. This will mean I will land at work with approx 46/47%, and should there be an issue with the work charger, I can still get home without a charge.

Would it be worth it, or in the long term would it not save the battery that much?

daheff

So I charge my phev to 100% twice nearly every day as I need that capacity to get to work (then charge) and when I get home so I can get to work the next day. So I’m guessing my battery will be screwed quite quickly then??

I’ve a Niro phev with capacity of 8.9kw/58km range (although real range is more like 45km). Work is 30km away

SlowBlowin

Deleted User wrote: »

OH the irony, all the abuse I got when I suggested people take better care of their batteries, like not charging to 100% if People didn't need to, watch the heat etc.

Oh but Nissan knew better than me and that's why the Leaf has a BMS ! lol

Yes I got the same.

Be good to keep this thread on a purely technical footing..

corks finest

NIMAN wrote:

I still have 12 bars, but since I now have a work charger I might start charging overnight to 80% instead of 100. This will mean I will land at work with approx 46/47%, and should there be an issue with the work charger, I can still get home without a charge.

Forgive my ignorance,I drive a hybrid,but when charging an ev can you set it to charge at a set percentage and not charge further?

tedpan

My leaf has 138k kms. It's a 151 gen 1.5, it lost 1 bar 3 months ago at 130k. I do about 100kms a day, always charge up to 100% and use the chademo 2-3 times a week.

I have 90% battery according to leaf spy. As long as I only use one bar every 130k kms I'll be happy

NIMAN

corks finest wrote: »

Forgive my ignorance,I drive a hybrid,but when charging an ev can you set it to charge at a set percentage and not charge further?

In the Leaf you can, there is a setting to stop at 80%.

NIMAN

tedpan wrote: »

My leaf has 138k kms. It's a 151 gen 1.5, it lost 1 bar 3 months ago at 130k. I do about 100kms a day, always charge up to 100% and use the chademo 2-3 times a week.

I have 90% battery according to leaf spy. As long as I only use one bar every 130k kms I'll be happy

Once you lose the 1st bar how does the chemistry work?
When will the next go approximately?

Soarer

In the Leaf, the first bar goes at 15% loss, then every 7.5% after that I think.

tedpan

NIMAN wrote:

Once you lose the 1st bar how does the chemistry work? When will the next go approximately?

Soarer wrote:

In the Leaf, the first bar goes at 15% loss, then every 7.5% after that I think.

I'm not sure on the technical side, but I haven't noticed significant range loss. Still getting around 120kms on a full charge, which is very close to what I got at the start.

NIMAN

tedpan wrote: »

I'm not sure on the technical side, but I haven't noticed significant range loss. Still getting around 120kms on a full charge, which is very close to what I got at the start.

Is this real 120km or what the guessometer is telling you?

tedpan

NIMAN wrote:

Is this real 120km or what the guessometer is telling you?

Real, I don't use the gom. If I drive normally in D, around 100kms, economically is around 120kms.

rivegauche

My Colleague told me last week that his nearly 3 year old Zoe has a SOH value of between 96 and 98%. It appears that battery degradation isn't a problem on the Zoe in the same way it is on the Leaf.
I note that the new e-208 and e-corsa have water cooling. Apart from needing to cool the battery during fast charging it seems like overkill.

Lumen

rivegauche wrote: »

My Colleague told me last week that his nearly 3 year old Zoe has a SOH value of between 96 and 98%. It appears that battery degradation isn't a problem on the Zoe in the same way it is on the Leaf.
I note that the new e-208 and e-corsa have water cooling. Apart from needing to cool the battery during fast charging it seems like overkill.

Does the Zoe have a top buffer?

Active temperature management (cooling and heating) is almost essential for a modern fast charging EV as far as I can tell. But it's difficult to be sure about any of this because the tech is defended for competitiveness reasons, and the industry doesn't want potential customers distracted by degradation anxiety just as they're getting over range anxiety.

tedpan

rivegauche wrote:

My Colleague told me last week that his nearly 3 year old Zoe has a SOH value of between 96 and 98%. It appears that battery degradation isn't a problem on the Zoe in the same way it is on the Leaf. I note that the new e-208 and e-corsa have water cooling. Apart from needing to cool the battery during fast charging it seems like overkill.

How many kms has he done? The 1st gen leaf had significant battery issues, as I said I'm happy with one bar lost every 130,000 kms!

Mike9832

tedpan wrote: »

How many kms has he done? The 1st gen leaf had significant battery issues, as I said I'm happy with one bar lost every 130,000 kms!

All about cost with Nissan, that awful reputation could have easily been avoided, but didn't want to spend a cent, has given EVs a bad name

Thats all it boils down to for everyone, cost

Cheap batteries fix everything

No one has a superior battery, it's just Audi etc can afford to absorb non useable battery cost and care about image

Once batteries get way cheaper, degradation will be a non issue

They will put in a 80kWh pack ( same cost as 40kWh today) and battery will stay between 10-90% forever, 300k km covered and battery will still be at 100% SOH

Its happening already in PHEVs

New Mercedes PHEVs have a 33% buffer, cells will never go below 15% or above 85%, they will not degrade for a long long time

Soarer

Mike9832 wrote: »

All about cost with Nissan, that awful reputation could have easily been avoided, but didn't want to spend a cent, has given EVs a bad name

No it hasn't!

EVs have never been so popular. I've seen more Kona EVs than I ever have Ioniqs.

EV's are flying out the doors everywhere, when dealers can get stock.

Mike9832

Soarer wrote: »

No it hasn't!

EVs have never been so popular. I've seen more Kona EVs than I ever have Ioniqs.

EV's are flying out the doors everywhere, when dealers can get stock.

9 years later

Soarer

Mike9832 wrote: »

9 years later

Nissan only “ruined the reputation of EVs” with rapidgate on the L40.
Before that, they were by far and away the pioneers in EVs...as can be seen by the amount of L24s and L30s on the road.

The L24 and L30 prices are holding firm in the secondhand market.
And the L40 is still flying out the door.
As will the L62, despite the pricing.

I bet a lot of manufacturers wish they could have their reputation so badly tarnished!

Mike9832

Soarer wrote: »

Nissan only “ruined the reputation of EVs” with rapidgate on the L40.
Before that, they were by far and away the pioneers in EVs...as can be seen by the amount of L24s and L30s on the road.

The L24 and L30 prices are holding firm in the secondhand market.
And the L40 is still flying out the door.
As will the L62, despite the pricing.

I bet a lot of manufacturers wish they could have their reputation so badly tarnished!

Those consumers don't know any better, enthusiasts with any bit of knowledge know of Nissans issues and wouldnt touch a Leaf40 or Leaf62

The average consumer still thinks electric car batteries are crap

They think they are like phone batteries and shot after a few years, when that couldnt be less true

Heard of these Leafs losing bars and cant even do 60km journey after 5 years

Nissan are to blame mostly for that negative pub talk

VW, Hyundai, Audi, Kia etc with great efforts are changing that

Lumen

Mike9832 wrote: »

Those consumers don't know any better, enthusiasts with any bit of knowledge know of Nissans issues and wouldnt touch a Leaf40 or Leaf62

Rapidgate is much less of an issue with the 62.

Too early to say whether degradation is better, maybe the bigger battery pack means less stress on the cells.

Chademo and price are the biggest offputters.

A larger battery such as a 60 Kwh will be cycled a hell of a lot less than the 24 Kwh which will help a lot + 10 - 20 % degradation will hardly be noticeable, it certainly won't be nearly as much of an issue as on a low range 24 - 30 Kw EV.

The real issues at 60+ Kwh won't be battery degradation but fast charging "times"

50 - 70 Kw DC charging is just simply not good enough today add to that the increased charge times with cold batteries.

The driver needs to be allowed to heat the battery up to allow max charging power, 20-35 Kw charging with a 50 Kw capable EV is just ridiculous, I know manufactures might think it counter intuitive to heat up a pack only to have to cool it again but I would rather cool it than wait an extra 20 mins or more !

I know top executives in these companies just can't understand this in their luxury Petrol and diesel cars !

Padraig Mor

Mike9832 wrote: »

Those consumers don't know any better, enthusiasts with any bit of knowledge know of Nissans issues and wouldnt touch a Leaf40 or Leaf62

More bull from you. I'm an enthusiast (with a damn sight more knowledge than you I'd imagine) and I'm perfectly happy with my Leaf 40.

Mike9832

Padraig Mor wrote: »

More bull from you. I'm an enthusiast (with a damn sight more knowledge than you I'd imagine) and I'm perfectly happy with my Leaf 40.

Thats my cue

unkel

SlowBlowin wrote: »

I think if you buy an actively cooled EV now, limit fast charging rates, and keep it between 20% and 80% the battery should out last the car.

It depends on how you define out last the car. Let's say an average EV will last 15 years before it is scrapped and let's say that at the very end of it's life it still has a SOH of 60%. I'd say you are being conservative there! Even if charged every cycle from say 10% to say 95% (BMS won't let you charge higher), the car does 15kWh/100km and you drive 20k km per year (25% more than the national average)

Then you will have 88 cycles per year, or 1,324 over the 15 year lifetime of the car



Worst case scenario in that picture is cycling between 25% and 100%. What we do above is probably slightly better. Yet after 4,400 cycles (equivalent of our car when it is 50 years old), it still has 78% capacity retention!

Now I know that's a lab test at 1C (many EVs can charge and discharge faster than that) and I know that's at a constant 20C temp, but going forward I'd say we will see very, very few EVs that will need a battery replacement. I'd say most batteries of EVs sold today will still be >60% SOH after 15 years. We will see!

krissovo

Just out of interest what would be better for battery health?

1 - Charge every weekday to 80% from ~40%
2 - Charge every other week day to 90% from ~15%

liamog

It's all about balancing the utility of a car versus the "hassle" of charging.
Here's a good site which discuss details https://pushevs.com/2018/04/27/battery-charging-full-versus-partial/

During lab conditions for a specific battery (every battery is different, but the principal broadly holds),
If you cycle a battery from 10% to 90% it should last 1,500 cycles before it hits 70% SoH.
If you cycle the same battery from 20% to 80% it should last 3,500 cycles.

If that battery was in an Ioniq it would hit 70% SoH at 215,000km for 10%-90% and 377,000km for 20% to 80%.
Now imagine the 64kWh Kona, cycling from 10% to 90% would last 492,000km vs 862,000km.

As unkel has mentioned, reality is newer batteries behave differently, you can make them cheaper and lighter by sacrificing some cycle life.

unkel

krissovo wrote: »

Just out of interest what would be better for battery health?

1 - Charge every weekday to 80% from ~40%
2 - Charge every other week day to 90% from ~15%

The first. See my graph. Your first scenario is very close to the second best line (purple) where they cycle between 75% and 45%

But in practice the difference between both your scenarios will lead to one car having 75% SOH after 15 years and the other 73%. And a car cycled between 25% and 100% (indicated) maybe 65%. So it has zero economical value to do any of this careful charging to prolong battery life.

krissovo

So drive it like I stole it then:D

unkel

Yep. Don't worry about it, it'll be fine! All EVs for sale today (afaik) come with an 8 year warranty on the battery. So very little chance it is at lower than 70% by then even if you abuse it (drive like you stole it / only ever fast charge it, etc.) and if it was, they'll replace it. And who cares if a 15 year old EV that is being scrapped has 50% or 80% SOH?

handofdog

Some further questions if you don't mind.

I'm witnessing fairly rapid degradation - albeit over a small window of time.

On 19th August (not long after purchasing the car, Gen 1 Leaf) SOH was 64.85 and 9 bars.

Today (i.e. approx 14 days later) SOH has dropped by approx 1.5 to 63.33 and I've just noticed that I'm on 8 bars.

I think that I recall reading that charging with a granny cable can lead to incorrect SOH measurements but I can't find this link just now. Almost all charges to date have been via granny cable.

So

1. Should I be concerned about this apparent rapid (to me anyway) SOH degradation? Or can this be attributed to the granny cable charging?

2. If so, is there anything that I can do to slow down the SOH decline?

Here's some background data

• The first week I would have been charging to 100% from 7pm to whenever it finished (wife doesn't want cable through window at night time) and recently I'm charging to 80% (again, starting at approx 7pm). i.e. for 1st week car could have been sitting overnight at 100% which I've since been led to believe is a bad idea.
• Daily commute is 2km to drop off child + 10km to work followed by 9km to get home. Sometimes I would go home at lunch as well (18km round trip).
• I was initially trying to get 3 days between charges so I'd charge to 100% and then it could be very low (15km GOM left) before re-charging. I now intend to charge to 80% every 2nd day.
• I don't tend to turn on climate control but the last 2 Saturdays we have driven approx 40km round trip and climate control would have been on full. Would this contribute to SOH decline?

I do realise that I'm dealing with a very small dataset - perhaps too small to draw any conclusions - but I think it's best to ask anyway. Apologies if some of these questions seem obvious, I'm very new to EVs!

Thanks in advance. Cheers

AhHaor

1. Should I be concerned about this apparent rapid (to me anyway) SOH degradation? Or can this be attributed to the granny cable charging?

SOH fluctuates greatly, and you'll notice it go up in the cold weather. It isn't caused by granny cable charging, however giving it 30 minutes on a fast charger can help

2. If so, is there anything that I can do to slow down the SOH decline?


The best thing you can do is just enjoy the car and use as required, these batteries are very robust and worrying about minute details isn't going to affect them.

What range and efficiency are you getting if you mind me asking and what is your battery capacity after a charge to 100%

handofdog

AhHaor wrote: »

The best thing you can do is just enjoy the car and use as required, these batteries are very robust and worrying about minute details isn't going to affect them.

What range and efficiency are you getting if you mind me asking and what is your battery capacity after a charge to 100%

Thanks! I'm certainly enjoying driving it...



The GOM estimates 102km (111km ECO) at 100%. Realistically this seems to be approx 80km.



Carwings reports .22kWh/mile (i.e. approc .14 kWh/km)


I think the capacity was reported as 15.2kWh on leaf spy at 100% but I can't be certain. It's claiming 7.9kWh remaining at 55.2% SOC so it might be 14.2kWh at full.


Cheers.

Thegalwayman

How much is a new battery?

unkel

Thegalwayman wrote: »

How much is a new battery?

Free under warranty. As long as the car is under 8 years old. If it is over 8 years old, it would not be an economic repair to replace a battery. Best to sell on as is with a limited range, or scrap the car (you will get thousands back for the battery). And there are plenty of options to refurbish the battery. Many companies are starting to specialise in that now. Can even do it DIY if you know what you are doing

Very unlikely though that an EV sold today will be scrapped because the battery range is too limited. Far more likely that when the car is end of life at say 15 years old, that the battery is taken out and will have another 15 year life as grid or home attached storage

tedpan

Thegalwayman wrote:

How much is a new battery?

Nissan have always tried to turn me off a new battery saying trade up for a new car instead. Apparently somewhere between 6 and 8k when I pushed them for an answer. Not sure if that includes the trade in of the old battery.

unkel

tedpan wrote: »

Nissan have always tried to turn me off a new battery saying trade up for a new car instead. Apparently somewhere between 6 and 8k when I pushed them for an answer. Not sure if that includes the trade in of the old battery.

I don't think anyone has ever paid for a battery replacement for an EV in this country. To do so would be a financial mistake.

SlowBlowin

US Leaf battery replacement/upgrade.

https://fenix.systems/leafbattery

krissovo

tedpan wrote: »

My leaf has 138k kms. It's a 151 gen 1.5, it lost 1 bar 3 months ago at 130k. I do about 100kms a day, always charge up to 100% and use the chademo 2-3 times a week.

I have 90% battery according to leaf spy. As long as I only use one bar every 130k kms I'll be happy

Similar results to the Ionic that Bjorn did the 1000km's challenge in. That had 92k on the clock.

Interesting part where he got his thermal camera out to view the hbattery cooling fan expelling the heat to the back.

Not a very scientific "guess" as to the actual degradation rate.......

i3 hasn't reached this level of Kms yet , it has 65,600 Kms and showing the same 29.6 Kwh as it did when I got it. it's a 171.

Leaf at almost 3 years and 85,000 was showing around 8-10% loss and I noticed the low battery warning coming on earlier and I had to drive it slower sometimes.

Duckjob

liamog wrote: »

It's all about balancing the utility of a car versus the "hassle" of charging.
Here's a good site which discuss details https://pushevs.com/2018/04/27/battery-charging-full-versus-partial/

I found very surprising that cycling from 100% to 20% was 1,000 cycles whereas cycling 80% to 0% was 3,000 cycles.

I was always under the impression that the running an EV battery low was far more stressful to it than charging it high. You learn something new everyday!

Mupchease

Anybody know what it’s like for an egolf ?

charlieIRL

Mupchease wrote: »

Anybody know what it’s like for an egolf ?

Hard to know, there’s very few 2015/16 ones here, no 2017 and a few 2018’s so too new to tell.