# The 40KWH Battery Topic

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I do not keep the car in the garage. We use our garage for projects. It sits in the sun above half the day. The car is white so that probability helps.

Hi all, I am interested in your opinion...

A free "fast" DC public charger has been opened recently near my location, it can give up to 18kwh to my 2018 Leaf. What do you think will this negatively affect my battery long term if I use it once per week let's say to top up from 30 to 80%. Approx 1h of charging.

Usually when travelling we are putting stress on a battery discharging fast then charging fast then discharging fast again, but this scenario would not have any such demands, just simple 2min drive to the charger, leave it for 1h and then 2min back home.

I could also use the AC 6.6kw option but it would take 3 times longer to do the same charge. Is it worth it if I plan to keep this car for a long time?

My current SOH is 87%.

Astral said:
Hi all, I am interested in your opinion...

A free "fast" DC public charger has been opened recently near my location, it can give up to 18kwh to my 2018 Leaf. What do you think will this negatively affect my battery long term if I use it once per week let's say to top up from 30 to 80%. Approx 1h of charging.

Usually when travelling we are putting stress on a battery discharging fast then charging fast then discharging fast again, but this scenario would not have any such demands, just simple 2min drive to the charger, leave it for 1h and then 2min back home.

I could also use the AC 6.6kw option but it would take 3 times longer to do the same charge. Is it worth it if I plan to keep this car for a long time?

My current SOH is 87%.

18 KW corresponds to a C rate of 0.5, which should not cause problems. The only key issue is the temperature. So it all depends on your ambient temperature. If the battery is at 20-25 degree celcius before the charge and ends up with 30-35 degree celcius after the charge i would not worry about it.

But if the ambient temperature is already at 35 degrees, then its another issue.

aneesh84 said:
But if the ambient temperature is already at 35 degrees, then its another issue.
Hit the nail on the head.

OK thanks. Why is 35c considered too much? What is the standard operating temperature of the battery pack?

Do you think there is any other issue other then temp? Googling I found this (sorry it's a bit long but maybe informative for some):

Fast charging, especially when done daily or frequently, can have negative effects on an electric car battery's overall health and longevity. While the rise in battery temperature is one factor, there are also other reasons why fast charging on a regular basis is considered detrimental to the battery:

Heat Generation: Fast charging generates more heat within the battery cells due to the higher charging currents. Excessive heat can accelerate the degradation of the battery's chemistry and lead to a reduction in its capacity over time. Elevated temperatures can also contribute to other forms of damage, such as electrolyte decomposition and thermal runaway.
Chemical Reactions: Fast charging causes more chemical reactions to occur within the battery cells. These reactions can result in the buildup of undesirable compounds, which can hinder the battery's performance and contribute to capacity loss.
Stress on Battery Cells: High charging currents and rapid charging can subject the battery cells to higher levels of stress. This stress can lead to mechanical damage within the cells, affecting their long-term durability.
Voltage and Current Spikes: Fast charging can lead to voltage and current spikes that may impact the battery's internal components and the overall battery management system. These spikes can cause wear and tear on the battery components.
Irreversible Lithium Plating: Rapid charging at low states of charge can lead to the deposition of lithium metal (lithium plating) on the anode. This can create a condition known as "lithium plating" which reduces the battery's capacity and overall performance over time.
Degradation of Electrode Materials: Faster charging can contribute to the degradation of the anode and cathode materials in the battery cells, leading to a decrease in the battery's capacity and performance.

It's important to note that manufacturers are aware of these concerns and design battery management systems to mitigate the impact of fast charging. These systems aim to balance charging rates, manage heat dissipation, and optimize the charging process to minimize battery degradation. However, even with advanced battery management systems, the cumulative effects of frequent fast charging can still contribute to reduced battery life over the long term.

To maximize the lifespan of an electric car battery, it's recommended to use fast charging sparingly and primarily rely on slower, regular charging for daily use. This approach helps to minimize the stress and heat generated during charging, which can extend the battery's overall health and longevity.

So at the end of this, my question is, can we consider 18kwh as fast charging in my case?

Call it medium rate.

Using the charger the way you mentioned probably won't have any severe effects on the battery so it all depends on what it is worth to have a car at xx% SOH vs (xx-1)% SOH in a few years. Or something like that. No one an tell you exactly what the difference will be but my guess is that it will be small.

Thank you, nevertheless I will try to use it only when necessary.

Our 2018 40kWh battery was slow charged 1550 times and 8 times fast in 60.000 miles and SOH is 85% and 3 cell pairs are weak.

hornstudio said:
Our 2018 40kWh battery was slow charged 1550 times and 8 times fast in 60.000 miles and SOH is 85% and 3 cell pairs are weak.

Do you live in a very hot climate? what mV cell difference you see and at what SOH?

Do you charge to 100% or 80%?

The LEAF pack does not have thermal control, so it is up to the owner to do what they can/choose to do to mitigate pack temperatures excursions.

Pack heating is due to charging, driving, and ambient. The more aggressive the driving or higher rate the charging, the more heat in the pack. OP: you can only manage this issue if you know the pack temperature, and the gauge in the LEAF is not good enough. Get an OBD2 adapter and pay the couple of dollars for TorquePro App. If your charging session ends up with a pack temp of around 75F or less you are in good shape to minimize the rate of long term degradation.

This is summer, so discussion is focused on high temperatures. In cold winter the same problem exists in reverse: it is a bad idea to use 0.5 C-rate charging into a cold pack

You are looking for a magic temperature threshold, but it does not exist. As pack temps climb, degradation accelerates. In the winter as pack temps drop, the degradation accelerates. Do your best to keep the pack in the 50F - 75F range. Here is the most useful and important point: high (or low) pack temps are particularly a problem at SoC over 85% -- ish, and particularly so when the pack stews in those conditions for hours. If you could charge the pack quickly to 90% SoC and then cool off the pack within an hour, you would not have a worry. But you cannot, so try to avoid that behavior.

Oh -- don't sweat a hot pack day here or there. If it is most days -- not so great.

It is possible to 'manage' pack temperature so long as your climate is not too extreme, but it can be annoying. Do yourself a favor and next time you buy a car, get an EV with thermal control.

-----
The underlying arithmetic:
18 kW charging dumps 4x the heat into the pack as 9 kW
36 kW charging dumps 16x the heat into the pack as 9 kW

I wanted an EV and I wanted a cheap one - the one I can actually afford. So I guess you get what you pay for and now I am dealing with this as everyone else here. So far actually it was quite easy to live with a Leaf. 5 months passed, if it had thermal management and CCS charging, it would be a sweet sweet car.

Astral said:
So far actually it was quite easy to live with a Leaf. 5 months passed, if it had thermal management and CCS charging, it would be a sweet sweet car.
Pretty much sums up about 75% of the discussions on this Forum for the last 10+ years (with the rest seemingly about 12v battery behavior).
What's amazing is the Leaf platform has largely existed untouched (I put a Gen2 battery pack in a Gen1 Leaf: try that with any other EV) for over 10 years now, and (while it's not without it's faults) the latest battery packs will most likely provide many years of service with some common sense charging habits (like avoiding extreme heat and extreme cold).

Astral said:
Thank you, nevertheless I will try to use it only when necessary.
I would just use it whenever you want: when free DC charging was still available at Lidl Belgium. I made sure to make use of it, so I drove through Belgium instead of the Netherlands when going to South Holland.

Those chargers where also limited to 20kW which meant getting 18kW and honestly: that isn't considering fast charging speed at all! You can get 22kW from AC if the car supported, and that isn't considered fast charging. But still faster than the 18kW of the free DC charger.

On my trip to Austria, I tried using the free DC chargers from IKEA: with the idea, that it would not inflect any potential extra degradation. But I guess, in the end of the day it would not matter much. You lose a lot of time by depending of free DC chargers.....

But you save quite some money: if I was living in any city with free DC chargers, than I would just go there once a week and charge to 90% max. Because 1kWh is atleast € 0,40 when charging at home, at public AC chargers.

aneesh84 said:
hornstudio said:
Our 2018 40kWh battery was slow charged 1550 times and 8 times fast in 60.000 miles and SOH is 85% and 3 cell pairs are weak.

Do you live in a very hot climate? what mV cell difference you see and at what SOH?

Do you charge to 100% or 80%?

Car came from Austria. So average temperature. It was maybe unneccessarily charged too often or too early to 100% (of course).

Car is now at Nissan to get free repair of cell pairs, hopefully.

Symptoms: if you run it around 20% SOC and drive around 60mph its SOC sweeps around +-10-20% and if you push the metal power will be reduced like on turtle mode.

I've dipped my toes in the EV world about a month ago by impulse acquiring a 2018 SL with a really nice Carfax.
(single owner, lady, averaged a bit over 3000 miles annually. Car is immaculate)

So I've driven every day for about 4 weeks and knew very little until I found this site. I'm on page 31 of this thread and sponging Leaf-Knowledge nightly.

Last night I charged (trickle) to 100% for the first time just to get some answers that the first 31 pages were begging for.
I'm no expert, if course, but I think I snagged a good one? Especially considering the ~6 year old car has spent it's life in tropical (HOT) Texas?

Welcome. And yes, you got a good one. SOH is unremarkable for a Northern state, but good for Texas. The pack is well-balanced, probably from lots of charges to 100%, which you should avoid in Summer.

Thanks for the feedback.
That's only it's second charge to 100% this summer, I suspect.

But who knows what the good lady that cared for it did for all those years?

The reason for the impulse is just my 65 year long interest/passion for all things with wheels. And there's now more than a decade of me watching from the sidelines as the EV has mechanically progressed from the.... well, original Leaf, to the explosion of the current releases. Fascinating.

I think I stole the car, relatively speaking. It was listed several thou\$and less than what other similar condition Leafs are in my area. (Especially considering it is the SL trim with the tech package)

Again, thanks for the reply. I should stop rambling off topic.

On topic: By page 33 of this thread, a newbie like myself quickly progressed from "what is Leafspy", to "Uhoh, these batteries are a disaster" to "wait! Breath. Maybe it's not quite what you first thought", and now to "not bad. Not bad at all. This thing has a lot of life left in it".

My daily commute is ~50 miles. It easily fits the mission. I have other cars/trucks for when it wouldn't.

SageBrush said:
The LEAF pack does not have thermal control, so it is up to the owner to do what they can/choose to do to mitigate pack temperatures excursions.

Pack heating is due to charging, driving, and ambient. The more aggressive the driving or higher rate the charging, the more heat in the pack. OP: you can only manage this issue if you know the pack temperature, and the gauge in the LEAF is not good enough. Get an OBD2 adapter and pay the couple of dollars for TorquePro App. If your charging session ends up with a pack temp of around 75F or less you are in good shape to minimize the rate of long term degradation.

This is summer, so discussion is focused on high temperatures. In cold winter the same problem exists in reverse: it is a bad idea to use 0.5 C-rate charging into a cold pack

You are looking for a magic temperature threshold, but it does not exist. As pack temps climb, degradation accelerates. In the winter as pack temps drop, the degradation accelerates. Do your best to keep the pack in the 50F - 75F range. Here is the most useful and important point: high (or low) pack temps are particularly a problem at SoC over 85% -- ish, and particularly so when the pack stews in those conditions for hours. If you could charge the pack quickly to 90% SoC and then cool off the pack within an hour, you would not have a worry. But you cannot, so try to avoid that behavior.

Oh -- don't sweat a hot pack day here or there. If it is most days -- not so great.

It is possible to 'manage' pack temperature so long as your climate is not too extreme, but it can be annoying. Do yourself a favor and next time you buy a car, get an EV with thermal control.

-----
The underlying arithmetic:
18 kW charging dumps 4x the heat into the pack as 9 kW
36 kW charging dumps 16x the heat into the pack as 9 kW

Very well said. However 75 Farenheit (24 degree celcius) is quite impractical since my ambient temperatures are higher than that during the day most of the summer. Based on data 2018 cars have the NCM chemistry which is much more heat tolerant than the previous generation LiMn chemistry used in 24 kwh and 30 kwh leafs. So I try to keep it within 86 Farenheit (30 degree celcius) as far as possible. The 40 Kwh leafs aged 5 years generally all have SOH between 85 to 90 percent no matter how they have been used.

Do we know at which temp the battery starts to rapidgate? https://ibb.co/NCCRYLb

Apparently it's in the red from 51c but seems to me the charging rates go down much sooner on fast charger.

aneesh84 said:
Very well said. However 75 Farenheit (24 degree celcius) is quite impractical since my ambient temperatures are higher than that during the day most of the summer.
My local climate has 90 - 100F daily temperatures for about two months a year. Lucky for us though, the car lives outside in the shade and nights are cooler so the pack tends to hang out at the average of peak and nadir daily temperatures when not driven, and some 5 - 10F degrees hotter depending on daily driving.

Now that we own an EV (Bolt) with thermal control the pack temp control is much less of an issue