[Miyata]

One thing I don't yet have a good grip over with respect to the EV tech - The battery life as it ages.

While every portal, news article, and scientific publication I have read claims there is no effect on useful battery life/range with age, I somehow find it hard to believe in the light of our everyday experience. The home UPS system, the laptop batteries, the smartphone batteries, the car batteries (other one!), etc they all die out and eventually need replacement.

So what exactly is different about the EV-tech batteries that make them immune to those issues that plague these other mentioned batteries?

Any thoughts or literature references on this?

[AutoNoob]

Originally Posted by Miyata

One thing I don't yet have a good grip over with respect to the EV tech - The battery life as it ages.

While every portal, news article, and scientific publication I have read claims there is no effect on useful battery life/range with age, I somehow find it hard to believe in the light of our everyday experience. The home UPS system, the laptop batteries, the smartphone batteries, the car batteries (other one!), etc they all die out and eventually need replacement.

So what exactly is different about the EV-tech batteries that make them immune to those issues that plague these other mentioned batteries?

Any thoughts or literature references on this?

You are correct, infact those who claim that EV batteries don't/ won't age, must be living in alternate world. With the tech available today, ageing is a very normal process in a battery's life cycle. Depending on the chemistry, design, usage etc. the ageing rates vary, but EV batteries do age.

I read somewhere, that a typical EV battery deteriorates only by 20~25% when it needs to be replaced. The remaining life is good for many other applications that need slower discharge / charge rates. There are many ongoing discussions/ studies for the afterlife of EV batteries. Some revolve around their usage as power bank in conjunction with Solar arrays or wind farms and some around more complex ideas.

Just a simple google search will give you thousands of news articles, research papers, manufacturers' official releases on this.

[avishar]

Tesla Battery Degradation data

Battery degradation is one of the biggest concerns for electric car owners and potential buyers, but data from Tesla battery packs have been very reassuring so far.

Now the latest data shows less than 10% degradation of the energy capacity after over 160,000 miles on Tesla’s battery packs.
A group of Tesla owners on the Dutch-Belgium Tesla Forum are gathering data from over 350 Tesla vehicles across the world and frequently updating it in a public Google file.

We have previously reported on the data, but they have since added many more vehicles and those vehicles have been driving a lot more – completing more battery cycles.

The data clearly shows that for the first 50,000 miles (100,000 km), most Tesla battery packs will lose about 5% of their capacity, but after the 50,000-mile mark, the capacity levels off and it looks like it could be difficult to make a pack degrade by another 5%.

The trend line currently suggests that the average battery pack could cycle through over 300,000 km (186,000) before coming close to 90% capacity.

Here are the relevant charts from the data gathering effort (full chart on the left and zoomed to 80% on the right):

Screen Shot 2018-04-14 at 2.56.15 PM Screen Shot 2018-04-14 at 2.54.02 PM
There are a few outlier battery packs out there and they tried to figure out why by gathering other data, like frequency of DC fast-charging and daily state of charge, but there’s no clear indication that any of those factors have any significant impact based on their data.

With this said, Jeff Dahn, a renowned battery researcher and the leader of Tesla’s research partnership through his battery-research group at Dalhousie University, said that he recommends charging to only 70% daily in order to extend battery life.

Tesla warns that it does not cover battery degradation from “battery usage” under its Model S and Model X warranty up to any specific level:

“The Battery, like all lithium-ion batteries, will experience gradual energy or power loss with time and use. Loss of Battery energy or power over time or due to or resulting from Battery usage, is NOT covered under this Battery Limited Warranty. See your owner documentation for important information on how to maximize the life and capacity of the Battery.”

But for the Model 3, Tesla introduced a warranty with a new 70% battery capacity retention guarantee.

The Model 3 is equipped with different battery cells and a new battery pack architecture, but if data from the Model S is any indication, it shouldn’t be an issue.

Electrek’s Take

Battery degradation is often a big concern for new electric vehicle buyers. To a certain degree, the Nissan Leaf might be to blame since it had a lot of issues in that regard, which is why Nissan has a much more comprehensive battery capacity warranty now.

A recent study shows that with the original 24 kWh pack loses about 20% of their capacity over 5 years and Nissan’s more recent 30 kWh battery pack loses capacity more quickly than the older pack:


But Tesla’s vehicles arguably have a much more advanced battery thermal management system than the Leaf and data from early Model S vehicles has been really encouraging as we can see above.

As for anecdotal data, my own Model S, which is one of the first 2,000 vehicles ever made, only lost about 6% capacity over 5 years.

CEO Elon Musk has been hyping even more potential for Tesla battery pack by once referring to a battery pack that Tesla was testing in the lab. He said that the company had simulated over 500,000 miles on it by repeatedly cycling it and that it was still operating at over 80% of its original capacity. At that point, the car itself is more likely to give up than the battery pack at this kind of mileage.

Nissan Leaf Battery Degradation data

In a recent study 283 Nissan Leafs manufactured between 2011 and 2017, had their SoH (State of Health) measured 1.382 times. The data is from 82 Nissan Leafs with 30 kWh batteries and 201 with the 24 kWh variants.

The measurements were made by using a OBD device and the Leaf Spy app.



The study has some interesting conclusions and I recommend you to read it (only 14 pages), but in this article I’ll focus on one:

30 kWh batteries are more affected by charge/discharge cycles (distance traveled) while 24 kWh versions were more affected by time.


Why are 30 kWh batteries more affected by charge/discharge cycles?

It’s not surprising that the 30 kWh versions suffer more from charge/discharge cycles, since they are more often charged to 100 %. Remember that the option to limit the charge to 80 % was removed when the 2014 model year debuted (to game EPA range ratings). This means that none Nissan Leaf with the 30 kWh battery has this option.

If you want to improve your electric car battery lifespan, you should know that it’s better to charge to 80 % and discharge till 0 % than to charge to 100 % and discharge to 20 %. Nonetheless, if you can use the battery between a SoC (State of Charge) of 80 and 20 % even better… And if you really want to take care of your battery, try to use it only between 70 and 20 %.

Moreover, having the battery sitting at 100 % SoC is worse with the 30 kWh version than it’s in the 24 kWh variants. Because in the same conditions the 30 kWh battery will likely be hotter. In the 24 kWh battery pack, each module has 4 cells, while in the 30 kWh variant there are 8 cells per module. A more dense battery pack will dissipate heat more slowly.



Why are 24 kWh batteries more affected by time?

It’s also not surprising that the 24 kWh versions are more affected by time and older Leafs show much higher degradation levels, since the “lizard” battery only arrived in 2014 with the 2015 Nissan Leaf.

24 kWh battery (model years 2011-2014): higher degradation levels
24 kWh battery (model years 2015-2016): lower degradation levels (“lizard battery”)
While the “lizard” battery cells remained with LMO cathodes, they had the electrolyte improved to be more heat tolerant. Only in 2016, Nissan finally started using NCM cathodes in their battery cells with the introduction of the 30 kWh battery version.

[Miyata]

After a bit of further digging around for more scoop on the topic of battery degradation with age and how exactly the EV-tech battery manages to perform better than the our everyday appliance battery, here more from at least one link -

...the EV manufacturer must guarantee the battery for eight years. This is done by oversizing the battery. When the battery is new, only about half of the available energy is utilized.

As the battery fades, more of the battery storage is demanded. The driving range stays constant but unknown to the driver, the battery is gradually charged to a higher level and discharged deeper to compensate for the fade.

Battery replacement may become necessary but the cost will be steep.

I have absolutely no idea about the technical competency or the degree of authority these guys have on the subject, but much of what they say does appear to stand to reason. Adding few more points that's in consonance with what AutoNoob and Avishar have shared:

The EV begins to impersonate a mobile phone in terms of obsolescence when the battery fades. This may be the time when the buyer is flooded with faster and flashier models;

...EV batteries operating in a warm climate faded prematurely

EV does not disclose the battery capacity to the driver and only reveals state-of-charge (SoC) in the form of driving range. This is done in part for fear of customer complaints should the capacity drop below the mandated level at the end of the warranty period. Less knowledge is often better.

[tarik.arora]

Having seen it in person, this thing looks damn cool. I wont mind having one in my garage just to flaunt that i am riding the EV wave (if i had the money). Maruti surely knows how to keep its market share intact even though it is the largest OEM by volumes.

Coming to the battery degradation part, the cost of battery replacement could be fairly high (20-25% of car cost?). In the initial years, till the range anxiety and battery tech improves in India, i see these cars as additional buys for people who have money. This may solve the pollution issue, but will increase the parking issues as people will not exchange their IC engine cars for these. The 'real' EV is still a good 15 years away. Remember initial year smart phone that were laggy, had battery issues, used to overheat and so on? Same is the case with these EV's, they will need time to come up to technology but the change has started!

[GTO]

Mod Note: Moving all battery degradation posts into a new thread for a dedicated discussion. Thanks!

[joybhowmik]

Originally Posted by tarik.arora

Remember initial year smart phone that were laggy, had battery issues, used to overheat and so on? Same is the case with these EV's, they will need time to come up to technology but the change has started!

Taking a lesson from hindsight, I think we ought to learn as a society. It's not good enough to say that batteries will degrade by such and such time to X% of the OEM capacity.
It will be enough if all the EV manufacturers embrace a standard battery charging interface though which does not depend on the kind of EV battery in use.

Remember As batteries age, there will also be evolution of battery technology - and I think that if open standards are de-rigeur, not only the customer wins, but so also does the EV manufacturer and the Battery manufacturer.

At the heart of the problem is entry barriers erected to keep competition out of the fray. However, if this insecurity continues to play out, the resultant insularity will anyway force such players out of the market when the developing technology matures.

We have seen this in the ICE era as well. Buyers tend to trust those manufacturers that support well known industry standards. They hate lock-in - as that basically says - "I don't trust you enough to be loyal to me".

[aashishnb]

The one most important factor IMO in battery life-cycle is the ambient temperature and use conditions.
While most of the research is based in Europe and US, as a logical extension, the batteries in EVs here should degrade much faster for many reasons - climate, stop-go usage pattern, etc. This would make the EV even more costlier than an ICE.

For many of us, the cost of replacing battery after say 3-4 years would be more than the entire petrol cost over those 3-4 years (considering the fact that the vehicle is going to be used largely for smaller trips within the city), effectively there being no savings.

[volkman10]

Volkswagen: Our Electric Car Batteries Last The Life Of The Car

VW To Guarantee 70% Battery Capacity For 8 Years Or 160,000 km

The goal for the upcoming MEB-based electric car is to guarantee a minimum capacity of 70% for eight years or 160,000 km (around 100,000 miles).


The new generation of models (I.D. family) are essentially cars built around the battery.

Link

[Ravi Parwan]

Originally Posted by joybhowmik

Taking a lesson from hindsight, I think we ought to learn as a society. It's not good enough to say that batteries will degrade by such and such time to X% of the OEM capacity.
It will be enough if all the EV manufacturers embrace a standard battery charging interface though which does not depend on the kind of EV battery in use.

Remember As batteries age, there will also be evolution of battery technology - and I think that if open standards are de-rigeur, not only the customer wins, but so also does the EV manufacturer and the Battery manufacturer.

....

There is a problem with this hypothesis. The interface has to be dependent on the battery type, it can't be independent. two noninvasive methods for battery charge estimation
1. The SoC of a battery is estimated on the voltage across its terminals, compared to the initial voltage achieved when the battery was new/ last charged to 100%. The gradual drop in voltage is "approximated" to the level of charge.
2. The SoC of a battery is estimated with the "net" current outgo from the battery. The storage is calculated on the last known full charged state of the battery. The net input and outgo of current is stored with the device and on the chip in the battery.

In first scenario, different types of batteries can't be linked to a single interface. batteries from the same manufacturer will also not behave in the same manner, if the underlying technology in the battery has been changed/upgraded.
In second scenario, the current outgo from a battery once charged will be stored on the battery chip, but if the battery is left to discharge, not sure if that will be lead to inaccuracy in charge calculations.
I believe the chemical batteries are on their way out, to be replaced by kinetic batteries. Only time will tell whether this is true or a chimera.

[COMMUTER]

EVs will make a great option to lease rather than own exactly due to this issue. The only way to break this deadlock is to get the EV manufacturers to provide swappable battery systems and open charged battery outlets where one can instantly swap his empty battery for a charged one. But they won't do this because they know that maintenance of EVs is an expensive issue.

I am being doubtful of the production of the EVs being viable after the diesel and petrol sources go dry.

[Lobogris]

I had a Toyota Prius hybrid for nearly 9 years. I drove it for around 200,000 kms.
There was no noticeable degradation of the battery at all. Toyota provided a 10 year warranty on the battery and very few hybrids have needed a battery change even after 10 years. Hence a 10 year time frame is reasonable for a high quality battery and around 5 years for a budget vehicle.

[COMMUTER]

Originally Posted by Lobogris

I had a Toyota Prius hybrid for nearly 9 years. I drove it for around 200,000 kms.
There was no noticeable degradation of the battery at all. Toyota provided a 10 year warranty on the battery and very few hybrids have needed a battery change even after 10 years. Hence a 10 year time frame is reasonable for a high quality battery and around 5 years for a budget vehicle.

A hybrid is a completely different breed from EV since its very hard to notice the degradation of the battery. We wouldn't be able to arrive at the miles travelled on battery and miles travelled when on full charge. This makes it difficult to judge the competence of the battery. When we say that our vehicle has lasted us for a long time, we might have been leaning more heavily on the advanced ICE technology.

[Lobogris]

Originally Posted by COMMUTER

A hybrid is a completely different breed from EV since its very hard to notice the degradation of the battery. We wouldn't be able to arrive at the miles travelled on battery and miles travelled when on full charge. This makes it difficult to judge the competence of the battery. When we say that our vehicle has lasted us for a long time, we might be leaning on the advanced ICE technology only.

I was afraid such arguments would crop up. It is true that a hybrid is different than a full EV but the Prius is a full hybrid. This means it is a fully functional electric vehicle capable of electric only propulsion. You start off only on electric most of the time. Even when you are using the ICE, the electric motor is providing additional power. The ICE is low powered in the Prius as the electric motor adds to the total power. If the battery degraded on the hybrid motor, you would immediately feel a loss of power. Still, I accept that the hybrid battery would have less wear than a fully electric one but I wanted to share the firsthand experience I had.

[ashlok94]

I believe that battery technology forms the heart of any EV vehicle. Battery manufacturers would not want to publicise that technology to other market players.
The IC engines came in a variety of configurations like the in-line 4s, 5s and 6s and also V4s, V6s, V8s and V10s (RIP V12s).
Most EV manufacturers today are using brushless motors and that is like the pinnacle of electric motors. The only way to distinguish performance in an EV remains the battery technology, it’s ability to support performance and its other characteristics.
Hence, OEM battery manufacturers would lose their edge if they open source their propriety hardware and software.
Case in point is the Nissan Leaf batteries. Poor thermal management systems have lead to a loss in sales.
Just my two bits.