Battery Degradation of a high mileage Leaf

[DougWantsALeaf]

A couple of the Nissan dealers in Chicago have an older 25KW Chademo. A bit painful to wait to charge with then, but better than L2.

 

[BillAinCT]

Yeah, almost 4 times better.

 

[Ez2517]

I saw a video recently where the creator of the teslalogger app (who analyzes degradation data from thousands of teslas) said that the worst you can do is to charge at low temperatures with low speed, because the cells then never reach their feelgood temperature. Also the CEO of EV Clinic, a workshop specialized on repairing EVs and EV batteries, says that he sees the worst degradation on cars that were charged primarily on AC.

 

[TronJockey]

Not according to my dealership: they argued with me, that they believe those 20kW fast chargers might have made the battery problems worse? But I'm sure, those battery problems where there already from the start.

It's quite possible that using a 10-20kWh DCFC charger will lead to accelerated battery degradation under certain conditions. The Leaf batteries (especially those of 40kWh or less) if driven for extended periods of time above 80 mph can raise core temperatures appreciably. This is especially true if done during periods of high ambient temperatures (>95F). With core temperatures elevated to well into the red zone, plugging into anything above the Level 2 (6.6kW) charger will risk accelerating degradation.
As well if using DCFC during cold weather, then Lithium plating becomes an issue. I've attached a study performed by the Alaska Center for Energy and Power detailing the Leaf's peculiar cold weather charging characteristics. They suggest only Level 1 or Level 2 charging at essentially any temperature under 49F.

 

[Oostenrijker]

It's quite possible that using a 10-20kWh DCFC charger will lead to accelerated battery degradation under certain conditions. The Leaf batteries (especially those of 40kWh or less) if driven for extended periods of time above 80 mph can raise core temperatures appreciably. This is especially true if done during periods of high ambient temperatures (>95F). With core temperatures elevated to well into the red zone, plugging into anything above the Level 2 (6.6kW) charger will risk accelerating degradation.
As well if using DCFC during cold weather, then Lithium plating becomes an issue. I've attached a study performed by the Alaska Center for Energy and Power detailing the Leaf's peculiar cold weather charging characteristics. They suggest only Level 1 or Level 2 charging at essentially any temperature under 49F.

Here the thing: I drive as snail, so the battery pack wouldn't overheat at all and I also observed. By charging at max 20kW, the temperature wouldn't increase a lot.

Too bad I can't set the fast charging speed manually: the thing with 20kW CHAdeMO chargers is, that they are usually free and being occupied by drivers of German EV's or Tesla's...

So I think, it would not be worth going through this hell everytime: I would wait quite a long time, and once it gets free? Then I would start charging my car and enter the IKEA restaurant. But it has happened more than once, that my charging session was ended all of a sudden.

Which means, someone who uses CCS just ended my charging session. Because that's how free triple chargers work: CCS and CHAdeMO charge the same power. If CHAdeMO is in use, CCS has to wait for me to finish. But with greet chargers, anyone can end your charging session.

I think I might skip they free 20kW chargers in the future, and either charge at 6.6kW at a 22kW Level 2 AC charger. Or just use 50kW fast chargers, because it isn't my fault? Nissan doesn't allow me to set a charging speed!

 

[RYoungberg]

I saw a video recently where the creator of the teslalogger app (who analyzes degradation data from thousands of teslas) said that the worst you can do is to charge at low temperatures with low speed, because the cells then never reach their feelgood temperature. Also the CEO of EV Clinic, a workshop specialized on repairing EVs and EV batteries, says that he sees the worst degradation on cars that were charged primarily on AC.

Do you have the link to that video? My son's 2014 LEAF has only been charged with 120V, sits outside - no garage, sometimes at subzero degree F, and at 90,000 miles has an amazingly strong battery. Seems to be the opposite of the Tesla advice.

 

[mux]

There's a lot of myths and legends going around SOH, but the reality is that there is not one definition of SOH and not one way to measure it 'accurately'. SOH can mean anything from remaining capacity to some derived value from internal resistance, to age, or all of the above weighted to come to a 'best guess' SOH.

And then Tesla does things differently, where they consider the pack at '100%' SOH even if there is significant degradation, because they don't count their buffer capacity as net capacity loss. Their definition of SOH is any loss of net capacity, not gross capacity. This is how you can have Tesla Model S batteries at 85%+ reported SOH, but (for that car very low) 50kW peak fast charging speeds, which would correspond to a much lower SOH when measured as equivalent internal resistance or gross capacity.

The Leaf does a net capacity test every time you quick charge long enough, and this is used as the main calibration point for SOH. It also tries to do polarization and internal resistance calculations when you do hard regen or acceleration, and it subtracts some constant percentage per year off the SOH due to aging. This means that if you never QC the Leaf, it will - depending on the generation and battery - over/underestimate real SOH. Or maybe by sheer luck it's exactly right

And these different ways in which cars measure degradation means cars respond differently to how you treat them, despite possibly the underlying battery chemistry doing the same thing. Some cars will seem to retain a higher SOH when regularly fast charged, some will show more degradation, and that leads to inferences by those working with the cars that can be mistaken. Or just hard to decipher.

 

[Oostenrijker]

The story came to an end today: I brought back the high mileage Leaf, and actually I will always remember my first experience with this Nissan Leaf. Because I enjoyed some benefits with car, one of those benefits was free charging. That didn't last long, but its priceless to have experienced that. Another thing I enjoyed, was getting discount at a Austrian Touristic Toll road. I even have canvas picture of this at my wall.



What I did not enjoy so much, was the constant stress that came with the battery problems: the weak cells where no fun, and I have experienced Turtle Mode twice. Especially in the winter the battery problems became much worse, whereas in the summer I still kinda could life with the limitations the weak cells gave me. Because I'm a amateur trained hypermiler. With my previous ICE vehicle I managed to get 30KM/L out of a gasoline in the summer, when I used expensive Shell V-Power. The gearbox might not have liked, my hypermiling so much...



That was the main reason I switched to electric driving: after 120.000km's that gearbox didn't feel smooth anymore, and changing the gear oil didn't help at all. But atleast I drove very cheap, and in the end I had a TCO of about € 0.17 a KM! I doubt I can ever match this with the Leaf? But charging costs went down this year and with a SOH of 89% I most likely won't need to fast charge as much, as I had to do before. So with € 0.05 a KM of electricity cost, driving the Leaf is much cheaper than a gasoline car in the same class. Gasoline cost would be approximately twice as much!

In the Netherlands gasoline isnt as cheap as in the USA: so expect to pay about € 2 for a litre of premium gasoline atleast, so with 18km/l that would mean € 0.11 a KM. Anyway now that I have a new Leaf, checked the battery pack throughly during the test driving with Leafspy. So I will be putting the ODB2 Dongle in a drawer, and I will respect the dash SoC. I want to drive, without worrying and as long as there isn't anything wrong? Then I don't see a reason to get out the dongle!



PS anyone able to spot the differences?



I got the bigger navigation screen in this car: it's really a big improvement, compared to the smaller screen I had in the high mileage Leaf.

 

[SageBrush]

Seems to be the opposite of the Tesla advice.

That is not 'Tesla advice,' that is some guy on the internet who posted an opinion contrary to research and expert opinion and large data sets.

 

[Oostenrijker]

Okay someone supposedly though, it was a good idea to import my previous high mileage Leaf. It has left the Netherlands since yesterday....

Why would anyone wanna import a Nissan Leaf with fried battery pack? Or they probably wouldn't have known? Anyone, it might be driving around in Africa now.

 

[kaiat]

Probably gone to Ukraine. Old Leafs and other EVs have been in high demand recently here in Norway. The cars are being exported to Ukraine. They don't mind about any faults, they fix them up. I have been contacted by three different people that wanted to buy my 2014 Leaf. I am not interested in selling though.

 

[Oostenrijker]

Probably gone to Ukraine. Old Leafs and other EVs have been in high demand recently here in Norway. The cars are being exported to Ukraine. They don't mind about any faults, they fix them up. I have been contacted by three different people that wanted to buy my 2014 Leaf. I am not interested in selling though.

Ukraine? I read stories, that owning an EV isn't a good idea there. Russia also attacks the electricity infrastructure.

 

[knightmb]

Electricity is needed to run gas pumps too, so it would not make much difference if you drove ICE or EV. Gas stations are easier targets in my opinion than trying to target every possible power outlet. One gallon of gas will get you further in an EV via generator than straight burning it in a ICE if gas is scarce or priced too high. Don't know if it has reached the mad max level there to be doing that...

 

[Drew21]

The Leaf does a net capacity test every time you quick charge long enough, and this is used as the main calibration point for SOH. It also tries to do polarization and internal resistance calculations when you do hard regen or acceleration, and it subtracts some constant percentage per year off the SOH due to aging. This means that if you never QC the Leaf, it will - depending on the generation and battery - over/underestimate real SOH

Hmm. This is interesting and not something I've heard before. Our 2014 Leaf still shows 11 bars (same as when we got it), but I have a sense that the range has declined a bit, although this could be the solely related to winter driving conditions. We've never done a QC in our 2.5 years of ownership; we L1 charge at home when necessary but the majority of charging occurs (L2 for free) at my wife's work.

We also don't do (any?) hard acceleration. I floored it one time for a couple seconds during our test drive and that's probably it. Yep, we're the annoying folks who are not exceeding the speed limit and holding you back. The roads we drive on have 25-45 mph limits so I can't see the need for hard acceleration, although I do add my own Fast and Furious exhaust noises.

Would you define hard regen as regularly hitting the fourth regen bubble? We do that pretty frequently as there's a long downhill before the turn onto our road, plus plenty of other hills around our local driving area.

 

[kaiat]

Ukraine? I read stories, that owning an EV isn't a good idea there. Russia also attacks the electricity infrastructure.

Ukraine has been dependant on Russian oil and gas, so there has been an interest in EVs even before the 2022 invasion over there. I don't know how it is to use an EV there under the current situation, but there is a steady stream of secondhand EVs going there from Norway and other countries too. If they couldn't use them, I guess they wouldn't buy them either...

 

[SageBrush]

And then Tesla does things differently, where they consider the pack at '100%' SOH even if there is significant degradation, because they don't count their buffer capacity as net capacity loss.

I think that is correct, but I cannot reconcile it with the observation that the degradation is not seen to increase once the buffer is used up. I'm thinking of the mostly European database of Tesla cars

 

[Oostenrijker]

This is the degradation test done by a Dutch car magazine: it was recorded last year, and published today.

 

[GTH]

Hi all,

I also bought a Nissan Leaf Tekna from 2019 in January 2020.

Time based degradation is not true for me! I don't (yet) have a LeafSpy
so can only use the BMS readouts. My car is now 4.25 years old and I am
convinced I have not lost more than 5% at most and probably a lot less.
This is properly checked on a long trip of 160 miles each year. Always
a summer trip and mostly at 50mph, so near the optimum. Nissan quote
239 miles at 50mph and 20 degC for my 62.5kWh battery.

After 160 miles the BMS said I had used:
68% in 2021 at car age 1.5 years (air temp 21 degC)
72% in 2022 at car age 2.5 years (air temp 18 degC - below optimum)
68% in 2023 at car age 3.5 years (air temp 25 degC)

Recently with temperatures around 18 degC I used 33% for 80 miles but
this is at a mix of speeds on local roads which compensates for the
slightly below optimum temperature.

In all cases I am still very close to the 239 miles quoted for 100%.

To be fair I do always drive for maximum range - I normally avoid using
more than 3 bars when accelerating but at this level I can keep up with
all normal drivers. On dual carriageways I try to restrict my speed to
the low 60s (mph) unless this causes issues with any other road users.

The rest is down to very carefully researched battery care as follows:

1) NO high speed charging ever (so far!)- I use 13A sockets always.
This avoids damage due to excessive battery temperatures.

2) ALWAYS charge to 100%, roughly once a week at home but more on
holiday. This ensures good cell balancing which is very important.

3) NEVER leave the SOC above 80%. I charge overnight and drive down to
90% or lower but then always down again to under 80% on the second day.

4) NEVER go below 25% SOC but if I get below 50% always charge back immediately to nearer 80%. This avoids risk of any weak cell damage.

The critical concerns to avoid are high battery temperatures from repeated fast charging and never leaving the SOC below 50% or above 80% for any length of time as different degradations occur under long term low or high charge. I was fortunate that, when Covid lockdowns hit, my SOC was around 80% and not above!

Whether this continued care will maintain my battery life long term I
will only find out in future years but so far it seems to be working.
My next test will be later this year when I do my 160 miles trip again.

 

[GTH]

Hi all,

I also bought a Nissan Leaf Tekna from 2019 in January 2020.

Time based degradation is not true for me! I don't (yet) have a LeafSpy
so can only use the BMS readouts. My car is now 4.25 years old and I am
convinced I have not lost more than 5% at most and probably a lot less.
This is properly checked on a long trip of 160 miles each year. Always
a summer trip and mostly at 50mph, so near the optimum. Nissan quote
239 miles at 50mph and 20 degC for my 62.5kWh battery.

After 160 miles the BMS said I had used:
68% in 2021 at car age 1.5 years (air temp 21 degC)
72% in 2022 at car age 2.5 years (air temp 18 degC - below optimum)
68% in 2023 at car age 3.5 years (air temp 25 degC)

Recently with temperatures around 18 degC I used 33% for 80 miles but
this is at a mix of speeds on local roads which compensates for the
slightly below optimum temperature.

In all cases I am still very close to the 239 miles quoted for 100%.

To be fair I do always drive for maximum range - I normally avoid using
more than 3 bars when accelerating but at this level I can keep up with
all normal drivers. On dual carriageways I try to restrict my speed to
the low 60s (mph) unless this causes issues with any other road users.

The rest is down to very carefully researched battery care as follows:

1) NO high speed charging ever (so far!)- I use 13A sockets always.
This avoids damage due to excessive battery temperatures.

2) ALWAYS charge to 100%, roughly once a week at home but more on
holiday. This ensures good cell balancing which is very important.

3) NEVER leave the SOC above 80%. I charge overnight and drive down to
90% or lower but then always down again to under 80% on the second day.

4) NEVER go below 25% SOC but if I get below 50% always charge back immediately to nearer 80%. This avoids risk of any weak cell damage.

The critical concerns to avoid are high battery temperatures from repeated fast charging and never leaving the SOC below 50% or above 80% for any length of time as different degradations occur under long term low or high charge. I was fortunate that, when Covid lockdowns hit, my SOC was around 80% and not above!

Whether this continued care will maintain my battery life long term I
will only find out in future years but so far it seems to be working.
My next test will be later this year when I do my 160 miles trip again.

 

[Oostenrijker]

This is properly checked on a long trip of 160 miles each year. Always
a summer trip and mostly at 50mph, so near the optimum. Nissan quote
239 miles at 50mph and 20 degC for my 62.5kWh battery.

After 160 miles the BMS said I had used:
68% in 2021 at car age 1.5 years (air temp 21 degC)
72% in 2022 at car age 2.5 years (air temp 18 degC - below optimum)
68% in 2023 at car age 3.5 years (air temp 25 degC)

I'm sorry to say so: but you are fooling yourself. You can't measure degradation like that, and it's bollocks that you would have only 5% battery degradation with a 2019...

If you haven't checked it in Leafspy, then it's no more then guesses: and your driving skills might have improved over the years, which maybe makes that you are driving more energy efficient now?

My current 2019 Leaf has a SoH of about 90% and the GoM showed 273km of range the other days at 100% SoC. After 100km of driving, my SoC was 72% and my energy consumption was 9.77kWh/100km.

But if I didn't tell my consumption: then people would think? Ow your Leaf is still able to drive 270km on a full charge... only the fact is, I was hypermiling the **** out of that day. So that I had enough juice, to get back home after returning with the airplane.